--- a/.eslintrc-test-paths.js
+++ b/.eslintrc-test-paths.js
@@ -258,17 +258,16 @@ const extraChromeTestPaths = [
   "gfx/layers/apz/test/mochitest/",
   "image/test/mochitest/",
   "layout/forms/test/",
   "layout/generic/test/",
   "layout/mathml/tests/",
   "layout/svg/tests/",
   "layout/xul/test/",
   "toolkit/components/aboutmemory/tests/",
-  "toolkit/components/osfile/tests/mochi/",
   "toolkit/components/printing/tests/",
   "toolkit/components/url-classifier/tests/mochitest/",
   "toolkit/components/viewsource/test/",
   "toolkit/components/windowcreator/test/",
   "toolkit/components/windowwatcher/test/",
   "toolkit/components/workerloader/tests/",
   "toolkit/content/tests/widgets/",
   "toolkit/profile/test/",

--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -305,17 +305,16 @@ module.exports = {
         "toolkit/components/glean/tests/browser/**",
         "toolkit/components/kvstore/kvstore.sys.mjs",
         "toolkit/components/lz4/lz4.js",
         "toolkit/components/messaging-system/**",
         "toolkit/components/mozintl/mozIntl.sys.mjs",
         "toolkit/components/narrate/Narrator.jsm",
         "toolkit/components/nimbus/**",
         "toolkit/components/normandy/**",
-        "toolkit/components/osfile/**",
         "toolkit/components/passwordmgr/**",
         "toolkit/components/pdfjs/**",
         "toolkit/components/pictureinpicture/**",
         "toolkit/components/places/**",
         "toolkit/components/printing/content/print*.*",
         "toolkit/components/processtools/tests/browser/browser_test_powerMetrics.js",
         "toolkit/components/promiseworker/**/PromiseWorker.*",
         "toolkit/components/prompts/**",
@@ -609,23 +608,16 @@ module.exports = {
       extends: ["plugin:react-hooks/recommended"],
       files: [
         "browser/components/newtab/**",
         "browser/components/pocket/**",
         "devtools/**",
       ],
     },
     {
-      // Turn off the osfile rule for osfile.
-      files: ["toolkit/components/osfile/**"],
-      rules: {
-        "mozilla/reject-osfile": "off",
-      },
-    },
-    {
       // Exempt files with these paths since they have to use http for full coverage
       files: httpTestingPaths.map(path => `${path}**`),
       rules: {
         "@microsoft/sdl/no-insecure-url": "off",
       },
     },
     {
       // Exempt all components and test files that explicitly want to test http urls from 'no-insecure-url' rule.

--- a/browser/base/content/test/performance/browser_startup.js
+++ b/browser/base/content/test/performance/browser_startup.js
@@ -97,17 +97,16 @@ const startupPhases = {
   // Things that are expected to be completely out of the startup path
   // and loaded lazily when used for the first time by the user should
   // be listed here.
   "before becoming idle": {
     denylist: {
       modules: new Set([
         "resource://gre/modules/AsyncPrefs.sys.mjs",
         "resource://gre/modules/LoginManagerContextMenu.sys.mjs",
-        "resource://gre/modules/osfile.jsm",
         "resource://pdf.js/PdfStreamConverter.sys.mjs",
       ]),
     },
   },
 };
 
 if (
   Services.prefs.getBoolPref("browser.startup.blankWindow") &&

--- a/browser/base/content/test/static/browser_all_files_referenced.js
+++ b/browser/base/content/test/static/browser_all_files_referenced.js
@@ -66,22 +66,16 @@ var gExceptionPaths = [
   // Nimbus schemas are referenced programmatically.
   "resource://nimbus/schemas/",
 
   // Activity stream schemas are referenced programmatically.
   "resource://activity-stream/schemas",
 
   // Localization file added programatically in featureCallout.jsm
   "resource://app/localization/en-US/browser/featureCallout.ftl",
-
-  // Will be removed in bug 1737308
-  "resource://gre/modules/lz4.js",
-  "resource://gre/modules/lz4_internal.js",
-  "resource://gre/modules/osfile.jsm",
-  "resource://gre/modules/osfile/",
 ];
 
 // These are not part of the omni.ja file, so we find them only when running
 // the test on a non-packaged build.
 if (AppConstants.platform == "macosx") {
   gExceptionPaths.push("resource://gre/res/cursors/");
   gExceptionPaths.push("resource://gre/res/touchbar/");
 }

--- a/docs/code-quality/lint/linters/eslint-plugin-mozilla.rst
+++ b/docs/code-quality/lint/linters/eslint-plugin-mozilla.rst
@@ -53,17 +53,16 @@ The plugin implements the following rule
    eslint-plugin-mozilla/reject-chromeutils-import-params
    eslint-plugin-mozilla/reject-eager-module-in-lazy-getter
    eslint-plugin-mozilla/reject-global-this
    eslint-plugin-mozilla/reject-globalThis-modification
    eslint-plugin-mozilla/reject-importGlobalProperties
    eslint-plugin-mozilla/reject-lazy-imports-into-globals
    eslint-plugin-mozilla/reject-mixing-eager-and-lazy
    eslint-plugin-mozilla/reject-multiple-getters-calls
-   eslint-plugin-mozilla/reject-osfile
    eslint-plugin-mozilla/reject-relative-requires
    eslint-plugin-mozilla/reject-requires-await
    eslint-plugin-mozilla/reject-scriptableunicodeconverter
    eslint-plugin-mozilla/reject-some-requires
    eslint-plugin-mozilla/reject-top-level-await
    eslint-plugin-mozilla/reject-import-system-module-from-non-system
    eslint-plugin-mozilla/use-cc-etc
    eslint-plugin-mozilla/use-chromeutils-generateqi

deleted file mode 100644
--- a/docs/code-quality/lint/linters/eslint-plugin-mozilla/reject-osfile.rst
+++ /dev/null
@@ -1,13 +0,0 @@
-reject-osfile
-=============
-
-Rejects calls into ``OS.File`` and ``OS.Path``. This is configured as a warning.
-You should use |IOUtils|_ and |PathUtils|_ respectively for new code.  If
-modifying old code, please consider swapping it in if possible; if this is
-tricky please ensure a bug is on file.
-
-.. |IOUtils| replace:: ``IOUtils``
-.. _IOUtils: https://searchfox.org/mozilla-central/source/dom/chrome-webidl/IOUtils.webidl
-
-.. |PathUtils| replace:: ``PathUtils``
-.. _PathUtils: https://searchfox.org/mozilla-central/source/dom/chrome-webidl/PathUtils.webidl

--- a/dom/system/OSFileConstants.cpp
+++ b/dom/system/OSFileConstants.cpp
@@ -830,107 +830,22 @@ bool OSFileConstantsService::DefineOSFil
 
   // Build OS.Constants.Sys
 
   JS::Rooted<JSObject*> objSys(aCx);
   if (!(objSys = GetOrCreateObjectProperty(aCx, objConstants, "Sys"))) {
     return false;
   }
 
-  nsCOMPtr<nsIXULRuntime> runtime =
-      do_GetService(XULRUNTIME_SERVICE_CONTRACTID);
-  if (runtime) {
-    nsAutoCString os;
-    DebugOnly<nsresult> rv = runtime->GetOS(os);
-    MOZ_ASSERT(NS_SUCCEEDED(rv));
-
-    JSString* strVersion = JS_NewStringCopyZ(aCx, os.get());
-    if (!strVersion) {
-      return false;
-    }
-
-    JS::Rooted<JS::Value> valVersion(aCx, JS::StringValue(strVersion));
-    if (!JS_SetProperty(aCx, objSys, "Name", valVersion)) {
-      return false;
-    }
-  }
-
-#if defined(DEBUG)
-  JS::Rooted<JS::Value> valDebug(aCx, JS::TrueValue());
-  if (!JS_SetProperty(aCx, objSys, "DEBUG", valDebug)) {
-    return false;
-  }
-#endif
-
-#if defined(HAVE_64BIT_BUILD)
-  JS::Rooted<JS::Value> valBits(aCx, JS::Int32Value(64));
-#else
-  JS::Rooted<JS::Value> valBits(aCx, JS::Int32Value(32));
-#endif  // defined (HAVE_64BIT_BUILD)
-  if (!JS_SetProperty(aCx, objSys, "bits", valBits)) {
-    return false;
-  }
-
   if (!JS_DefineProperty(
           aCx, objSys, "umask", mUserUmask,
           JSPROP_ENUMERATE | JSPROP_READONLY | JSPROP_PERMANENT)) {
     return false;
   }
 
-  // Build OS.Constants.Path
-
-  JS::Rooted<JSObject*> objPath(aCx);
-  if (!(objPath = GetOrCreateObjectProperty(aCx, objConstants, "Path"))) {
-    return false;
-  }
-
-  // Locate libxul
-  // Note that we don't actually provide the full path, only the name of the
-  // library, which is sufficient to link to the library using js-ctypes.
-
-#if defined(XP_MACOSX)
-  // Under MacOS X, for some reason, libxul is called simply "XUL",
-  // and we need to provide the full path.
-  nsAutoString libxul;
-  libxul.Append(mPaths->libDir);
-  libxul.AppendLiteral("/XUL");
-#else
-  // On other platforms, libxul is a library "xul" with regular
-  // library prefix/suffix.
-  nsAutoString libxul;
-  libxul.AppendLiteral(MOZ_DLL_PREFIX);
-  libxul.AppendLiteral("xul");
-  libxul.AppendLiteral(MOZ_DLL_SUFFIX);
-#endif  // defined(XP_MACOSX)
-
-  if (!SetStringProperty(aCx, objPath, "libxul", libxul)) {
-    return false;
-  }
-
-  if (!SetStringProperty(aCx, objPath, "libDir", mPaths->libDir)) {
-    return false;
-  }
-
-  if (!SetStringProperty(aCx, objPath, "tmpDir", mPaths->tmpDir)) {
-    return false;
-  }
-
-  // Configure profileDir only if it is available at this stage
-  if (!mPaths->profileDir.IsVoid() &&
-      !SetStringProperty(aCx, objPath, "profileDir", mPaths->profileDir)) {
-    return false;
-  }
-
-  // Configure localProfileDir only if it is available at this stage
-  if (!mPaths->localProfileDir.IsVoid() &&
-      !SetStringProperty(aCx, objPath, "localProfileDir",
-                         mPaths->localProfileDir)) {
-    return false;
-  }
-
   return true;
 }
 
 NS_IMPL_ISUPPORTS(OSFileConstantsService, nsIOSFileConstantsService,
                   nsIObserver)
 
 /* static */
 already_AddRefed<OSFileConstantsService> OSFileConstantsService::GetOrCreate() {

--- a/dom/system/moz.build
+++ b/dom/system/moz.build
@@ -3,19 +3,16 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 # This picks up *hapticfeedback* which is graveyard
 with Files("**"):
     BUG_COMPONENT = ("Core", "DOM: Core & HTML")
 
-with Files("*OSFile*"):
-    BUG_COMPONENT = ("Toolkit", "OS.File")
-
 with Files("*ocationProvider*"):
     BUG_COMPONENT = ("Core", "DOM: Geolocation")
 
 with Files("windows/*LocationProvider*"):
     BUG_COMPONENT = ("Core", "DOM: Geolocation")
 
 with Files("IOUtils*"):
     BUG_COMPONENT = ("Toolkit", "OS.File")

--- a/dom/system/tests/chrome.ini
+++ b/dom/system/tests/chrome.ini
@@ -1,9 +1,9 @@
 [DEFAULT]
+
+[test_constants.xhtml]
 support-files =
   worker_constants.js
-
-[test_constants.xhtml]
 [test_pathutils.html]
 [test_pathutils_worker.xhtml]
 support-files =
   pathutils_worker.js

--- a/dom/system/tests/ioutils/test_ioutils_read_write.html
+++ b/dom/system/tests/ioutils/test_ioutils_read_write.html
@@ -10,21 +10,16 @@
   <link rel="stylesheet" href="chrome://mochikit/content/tests/SimpleTest/test.css" />
   <script src="file_ioutils_test_fixtures.js"></script>
   <script>
     "use strict";
 
     const { Assert } = ChromeUtils.import("resource://testing-common/Assert.jsm");
     const { ObjectUtils } = ChromeUtils.import("resource://gre/modules/ObjectUtils.jsm");
 
-    // This is presently only used to test compatability between OS.File and
-    // IOUtils when it comes to writing compressed files. The import and the
-    // test `test_lz4_osfile_compat` can be removed with OS.File is removed.
-    const { OS } = ChromeUtils.import("resource://gre/modules/osfile.jsm");
-
     add_task(async function test_read_failure() {
       const doesNotExist = PathUtils.join(PathUtils.tempDir, "does_not_exist.tmp");
       await Assert.rejects(
         IOUtils.read(doesNotExist),
         /Could not open the file at .*/,
         "IOUtils::read rejects when file does not exist"
       );
     });
@@ -335,41 +330,16 @@
       const readEmptyRaw = await IOUtils.read(tmpFileName, { decompress: false });
       is(readEmptyRaw.length, 12, "Expected to read back just the LZ4 header");
       const expectedHeader = Uint8Array.of(109, 111, 122, 76, 122, 52, 48, 0, 0, 0, 0, 0); // "mozLz40\0\0\0\0"
       ok(readEmptyRaw.equals(expectedHeader), "Expected to read header with content length of 0");
 
       await cleanup(tmpFileName);
     });
 
-    add_task(async function test_lz4_osfile_compat() {
-      const osfileTmpFile = PathUtils.join(PathUtils.tempDir, "test_ioutils_lz4_compat_osfile.tmp");
-      const ioutilsTmpFile = PathUtils.join(PathUtils.tempDir, "test_ioutils_lz4_compat_ioutils.tmp");
-
-      info("Test OS.File and IOUtils write the same file with LZ4 compression enabled")
-      const repeatedBytes = Uint8Array.of(...new Array(50).fill(1));
-      let expectedBytes = 23;
-      let ioutilsBytes = await IOUtils.write(ioutilsTmpFile, repeatedBytes, { compress: true });
-      let osfileBytes = await OS.File.writeAtomic(osfileTmpFile, repeatedBytes, { compression: "lz4" });
-      is(ioutilsBytes, expectedBytes, "IOUtils writes the expected number of bytes for compression");
-      is(osfileBytes, ioutilsBytes, "OS.File and IOUtils write the same number of bytes for LZ4 compression");
-
-      info("Test OS.File can read a file compressed by IOUtils");
-      const osfileReadBytes = await OS.File.read(ioutilsTmpFile, { compression: "lz4" });
-      ok(osfileReadBytes.every(byte => byte === 1), "OS.File can read a file compressed by IOUtils");
-      is(osfileReadBytes.length, 50, "OS.File reads the right number of bytes from a file compressed by IOUtils")
-
-      info("Test IOUtils can read a file compressed by OS.File");
-      const ioutilsReadBytes = await IOUtils.read(osfileTmpFile, { decompress: true });
-      ok(ioutilsReadBytes.every(byte => byte === 1), "IOUtils can read a file compressed by OS.File");
-      is(ioutilsReadBytes.length, 50, "IOUtils reads the right number of bytes from a file compressed by OS.File")
-
-      await cleanup(osfileTmpFile, ioutilsTmpFile);
-    });
-
     add_task(async function test_lz4_bad_call() {
       const tmpFileName = PathUtils.join(PathUtils.tempDir, "test_ioutils_lz4_bad_call.tmp");
 
       info("Test decompression with invalid options");
       const varyingBytes = Uint8Array.of(...new Array(50).keys());
       let bytesWritten = await IOUtils.write(tmpFileName, varyingBytes, { compress: true });
       is(bytesWritten, 64, "Expected to write 64 bytes");
       await Assert.rejects(

--- a/dom/system/tests/ioutils/test_ioutils_read_write_utf8.html
+++ b/dom/system/tests/ioutils/test_ioutils_read_write_utf8.html
@@ -10,21 +10,16 @@
   <link rel="stylesheet" href="chrome://mochikit/content/tests/SimpleTest/test.css" />
   <script src="file_ioutils_test_fixtures.js"></script>
   <script>
     "use strict";
 
     const { Assert } = ChromeUtils.import("resource://testing-common/Assert.jsm");
     const { ObjectUtils } = ChromeUtils.import("resource://gre/modules/ObjectUtils.jsm");
 
-    // This is presently only used to test compatability between OS.File and
-    // IOUtils when it comes to writing compressed files. The import and the
-    // test `test_lz4_osfile_compat` can be removed with OS.File is removed.
-    const { OS } = ChromeUtils.import("resource://gre/modules/osfile.jsm");
-
     // This is an impossible sequence of bytes in an UTF-8 encoded file.
     // See section 3.5.3 of this text:
     // https://www.cl.cam.ac.uk/~mgk25/ucs/examples/UTF-8-test.txt
     const invalidUTF8 = Uint8Array.of(0xfe, 0xfe, 0xff, 0xff);
 
     add_task(async function test_read_utf8_failure() {
       info("Test attempt to read non-existent file (UTF8)");
       const doesNotExist = PathUtils.join(PathUtils.tempDir, "does_not_exist.tmp");
@@ -285,39 +280,16 @@
       const readEmpty = await IOUtils.readUTF8(tmpFileName, { decompress: true });
       is(readEmpty, empty, "IOUtils can write and read back empty buffers with LZ4");
       const readEmptyRaw = await IOUtils.readUTF8(tmpFileName, { decompress: false });
       is(readEmptyRaw.length, 12, "Expected to read back just the LZ4 header");
 
       await cleanup(tmpFileName);
     });
 
-    add_task(async function test_utf8_lz4_osfile_compat() {
-      const osfileTmpFile = PathUtils.join(PathUtils.tempDir, "test_ioutils_utf8_lz4_compat_osfile.tmp");
-      const ioutilsTmpFile = PathUtils.join(PathUtils.tempDir, "test_ioutils_utf8_lz4_compat_ioutils.tmp");
-
-      info("Test OS.File and IOUtils write the same UTF-8 file with LZ4 compression enabled")
-      const emoji = "☕️ ⚧️ 😀 🖖🏿 🤠 🏳️‍🌈 🥠 🏴‍☠️ 🪐";
-      let expectedBytes = 83;
-      let ioutilsBytes = await IOUtils.writeUTF8(ioutilsTmpFile, emoji, { compress: true });
-      let osfileBytes = await OS.File.writeAtomic(osfileTmpFile, emoji, { compression: "lz4" });
-      is(ioutilsBytes, expectedBytes, "IOUtils writes the expected number of bytes for compression");
-      is(osfileBytes, ioutilsBytes, "OS.File and IOUtils write the same number of bytes for LZ4 compression");
-
-      info("Test OS.File can read an UTF-8 file compressed by IOUtils");
-      const osfileReadStr = await OS.File.read(ioutilsTmpFile, { compression: "lz4", encoding: "utf-8" });
-      is(osfileReadStr, emoji, "OS.File can read an UTF-8 file compressed by IOUtils")
-
-      info("Test IOUtils can read an UTF-8 file compressed by OS.File");
-      const ioutilsReadString = await IOUtils.readUTF8(ioutilsTmpFile, { decompress: true });
-      is(ioutilsReadString, emoji, "IOUtils can read an UTF-8 file compressed by OS.File");
-
-      await cleanup(osfileTmpFile, ioutilsTmpFile);
-    });
-
     add_task(async function test_utf8_lz4_bad_call() {
       const tmpFileName = PathUtils.join(PathUtils.tempDir, "test_ioutils_utf8_lz4_bad_call.tmp");
 
       info("readUTF8 ignores the maxBytes option if provided");
       const emoji = "☕️ ⚧️ 😀 🖖🏿 🤠 🏳️‍🌈 🥠 🏴‍☠️ 🪐";
       let bytesWritten = await IOUtils.writeUTF8(tmpFileName, emoji, { compress: true });
       is(bytesWritten, 83, "Expected to write 83 bytes");
 

--- a/dom/system/tests/test_constants.xhtml
+++ b/dom/system/tests/test_constants.xhtml
@@ -11,31 +11,16 @@
   <script src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"/>
   <script type="application/javascript">
   <![CDATA[
 
 /* global OS */
 
 let worker;
 
-function test_xul() {
-  let lib;
-  isnot(null, OS.Constants.Path.libxul, "libxulpath is defined");
-  try {
-    lib = ctypes.open(OS.Constants.Path.libxul);
-    lib.declare("DumpJSStack", ctypes.default_abi, ctypes.void_t);
-  } catch (x) {
-    ok(false, "Could not open libxul " + x);
-  }
-  if (lib) {
-    lib.close();
-  }
-  ok(true, "test_xul: opened libxul successfully");
-}
-
 // Test that OS.Constants.libc is defined
 function test_libc() {
   isnot(null, OS.Constants.libc, "OS.Constants.libc is defined");
   is(0o001, OS.Constants.libc.S_IXOTH, "OS.Constants.libc.S_IXOTH is defined");
   is(0o002, OS.Constants.libc.S_IWOTH, "OS.Constants.libc.S_IWOTH is defined");
   is(0o007, OS.Constants.libc.S_IRWXO, "OS.Constants.libc.S_IRWXO is defined");
   is(0o010, OS.Constants.libc.S_IXGRP, "OS.Constants.libc.S_IXGRP is defined");
   is(0o020, OS.Constants.libc.S_IWGRP, "OS.Constants.libc.S_IWGRP is defined");
@@ -53,44 +38,35 @@ function test_Win() {
                            .getService(Ci.nsIXULRuntime);
   if(xulRuntime.OS == "Windows") {
     ok("Win" in OS.Constants, "OS.Constants.Win is defined");
     is(OS.Constants.Win.INVALID_HANDLE_VALUE, -1,
       "OS.Constants.Win.INVALID_HANDLE_VALUE is defined and correct");
   }
 }
 
-// Test that OS.Constants.Sys.DEBUG is set properly on main thread
-function test_debugBuildMainThread(isDebugBuild) {
-  is(isDebugBuild, !!OS.Constants.Sys.DEBUG, "OS.Constants.Sys.DEBUG is set properly on main thread");
-}
-
 // Test that OS.Constants.Sys.umask is set properly on main thread
 function test_umaskMainThread(umask) {
   is(umask, OS.Constants.Sys.umask,
      "OS.Constants.Sys.umask is set properly on main thread: " +
      ("0000"+umask.toString(8)).slice(-4));
 }
 
 var ctypes;
 function test() {
   ok(true, "test_constants.xhtml: Starting test");
 
   // Test 1: Load libxul from main thread
   Cc["@mozilla.org/net/osfileconstantsservice;1"].
     getService(Ci.nsIOSFileConstantsService).
     init();
   ({ctypes} = ChromeUtils.import("resource://gre/modules/ctypes.jsm"));
-  test_xul();
   test_libc();
   test_Win();
 
-  let isDebugBuild = Cc["@mozilla.org/xpcom/debug;1"]
-                            .getService(Ci.nsIDebug2).isDebugBuild;
-  test_debugBuildMainThread(isDebugBuild);
 
   let umask = Cc["@mozilla.org/system-info;1"].
     getService(Ci.nsIPropertyBag2).
     getProperty("umask");
   test_umaskMainThread(umask);
 
   // Test 2: Load libxul from chrome thread
   worker = new ChromeWorker("worker_constants.js");
@@ -118,17 +94,16 @@ function test() {
       SimpleTest.ok(false, "test_constants.xhtml: wrong message " + JSON.stringify(msg.data));
       return;
     }
   };
 
   // pass expected values that are unavailable off-main-thread
   // to the worker
   worker.postMessage({
-    isDebugBuild: isDebugBuild,
     umask: umask
   });
   ok(true, "test_constants.xhtml: Test in progress");
 };
 ]]>
   </script>
 
   <body xmlns="http://www.w3.org/1999/xhtml">

--- a/dom/system/tests/worker_constants.js
+++ b/dom/system/tests/worker_constants.js
@@ -10,23 +10,19 @@ function log(text) {
 function send(message) {
   self.postMessage(message);
 }
 
 self.onmessage = function(msg) {
   self.onmessage = function(msgInner) {
     log("ignored message " + JSON.stringify(msgInner.data));
   };
-  let { isDebugBuild, umask } = msg.data;
+  let { umask } = msg.data;
   try {
-    test_name();
-    test_xul();
-    test_debugBuildWorkerThread(isDebugBuild);
     test_umaskWorkerThread(umask);
-    test_bits();
   } catch (x) {
     log("Catching error: " + x);
     log("Stack: " + x.stack);
     log("Source: " + x.toSource());
     ok(false, x.toString() + "\n" + x.stack);
   }
   finish();
 };
@@ -40,56 +36,17 @@ function ok(condition, description) {
 }
 function is(a, b, description) {
   send({ kind: "is", a, b, description });
 }
 function isnot(a, b, description) {
   send({ kind: "isnot", a, b, description });
 }
 
-// Test that OS.Constants.Sys.Name is defined
-function test_name() {
-  isnot(null, OS.Constants.Sys.Name, "OS.Constants.Sys.Name is defined");
-}
-
-// Test that OS.Constants.Sys.DEBUG is set properly in ChromeWorker thread
-function test_debugBuildWorkerThread(isDebugBuild) {
-  is(
-    isDebugBuild,
-    !!OS.Constants.Sys.DEBUG,
-    "OS.Constants.Sys.DEBUG is set properly on worker thread"
-  );
-}
-
 // Test that OS.Constants.Sys.umask is set properly in ChromeWorker thread
 function test_umaskWorkerThread(umask) {
   is(
     umask,
     OS.Constants.Sys.umask,
     "OS.Constants.Sys.umask is set properly on worker thread: " +
       ("0000" + umask.toString(8)).slice(-4)
   );
 }
-
-// Test that OS.Constants.Path.libxul lets us open libxul
-function test_xul() {
-  let lib;
-  isnot(null, OS.Constants.Path.libxul, "libxul is defined");
-  try {
-    lib = ctypes.open(OS.Constants.Path.libxul);
-    lib.declare("DumpJSStack", ctypes.default_abi, ctypes.void_t);
-  } catch (x) {
-    ok(false, "test_xul: Could not open libxul: " + x);
-  }
-  if (lib) {
-    lib.close();
-  }
-  ok(true, "test_xul: opened libxul successfully");
-}
-
-// Check if the value of OS.Constants.Sys.bits is 32 or 64
-function test_bits() {
-  is(
-    OS.Constants.Sys.bits,
-    ctypes.int.ptr.size * 8,
-    "OS.Constants.Sys.bits is either 32 or 64"
-  );
-}

deleted file mode 100644
--- a/dom/webidl/NativeOSFileInternals.webidl
+++ /dev/null
@@ -1,60 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtaone at http://mozilla.org/MPL/2.0/. */
-
-/**
- * Options for nsINativeOSFileInternals::Read
- */
-[GenerateInit]
-dictionary NativeOSFileReadOptions
-{
-  /**
-   * If specified, convert the raw bytes to a String
-   * with the specified encoding. Otherwise, return
-   * the raw bytes as a TypedArray.
-   */
-  DOMString? encoding;
-
-  /**
-   * If specified, limit the number of bytes to read.
-   */
-  unsigned long long? bytes;
-};
-
-/**
- * Options for nsINativeOSFileInternals::WriteAtomic
- */
-[GenerateInit]
-dictionary NativeOSFileWriteAtomicOptions
-{
-  /**
-   * If specified, specify the number of bytes to write.
-   * NOTE: This takes (and should take) a uint64 here but the actual
-   * value is limited to int32. This needs to be fixed, see Bug 1063635.
-   */
-  unsigned long long? bytes;
-
-  /**
-   * If specified, write all data to a temporary file in the
-   * |tmpPath|. Else, write to the given path directly.
-   */
-  DOMString? tmpPath = null;
-
-  /**
-   * If specified and true, a failure will occur if the file
-   * already exists in the given path.
-   */
-  boolean noOverwrite = false;
-
-  /**
-   * If specified and true, this will sync any buffered data
-   * for the file to disk. This might be slower, but safer.
-   */
-  boolean flush = false;
-
-  /**
-   * If specified, this will backup the destination file as
-   * specified.
-   */
-  DOMString? backupTo = null;
-};

--- a/dom/webidl/moz.build
+++ b/dom/webidl/moz.build
@@ -224,19 +224,16 @@ with Files("MIDI*"):
     BUG_COMPONENT = ("Core", "DOM: Device Interfaces")
 
 with Files("Mouse*"):
     BUG_COMPONENT = ("Core", "DOM: UI Events & Focus Handling")
 
 with Files("MutationEvent.webidl"):
     BUG_COMPONENT = ("Core", "DOM: Events")
 
-with Files("NativeOSFileInternals.webidl"):
-    BUG_COMPONENT = ("Toolkit", "OS.File")
-
 with Files("NavigationPreloadManager.webidl"):
     BUG_COMPONENT = ("Core", "DOM: Service Workers")
 
 with Files("Net*"):
     BUG_COMPONENT = ("Core", "Networking")
 
 with Files("OfflineAudio*"):
     BUG_COMPONENT = ("Core", "Web Audio")
@@ -741,17 +738,16 @@ WEBIDL_FILES = [
     "MimeType.webidl",
     "MimeTypeArray.webidl",
     "MouseEvent.webidl",
     "MouseScrollEvent.webidl",
     "MozFrameLoaderOwner.webidl",
     "MutationEvent.webidl",
     "MutationObserver.webidl",
     "NamedNodeMap.webidl",
-    "NativeOSFileInternals.webidl",
     "NavigationPreloadManager.webidl",
     "Navigator.webidl",
     "NetErrorInfo.webidl",
     "NetworkInformation.webidl",
     "NetworkOptions.webidl",
     "NodeFilter.webidl",
     "NodeIterator.webidl",
     "NodeList.webidl",

--- a/js/xpconnect/tests/browser/browser_import_mapped_jsm.js
+++ b/js/xpconnect/tests/browser/browser_import_mapped_jsm.js
@@ -23,17 +23,16 @@ const JSMs = [
   "resource://gre/modules/FileUtils.jsm",
   "resource://gre/modules/LightweightThemeManager.jsm",
   "resource://gre/modules/NetUtil.jsm",
   "resource://gre/modules/PlacesUtils.jsm",
   "resource://gre/modules/PluralForm.jsm",
   "resource://gre/modules/PrivateBrowsingUtils.jsm",
   "resource://gre/modules/Timer.jsm",
   "resource://gre/modules/XPCOMUtils.jsm",
-  "resource://gre/modules/osfile.jsm",
   "resource://gre/modules/addons/XPIDatabase.jsm",
   "resource://gre/modules/addons/XPIProvider.jsm",
   "resource://gre/modules/addons/XPIInstall.jsm",
   "resource:///modules/BrowserWindowTracker.jsm",
 ];
 
 if (AppConstants.platform === "win") {
   JSMs.push("resource:///modules/WindowsJumpLists.jsm");

--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -619,19 +619,16 @@ pref("findbar.matchdiacritics", 0);
 pref("findbar.modalHighlight", false);
 
 // use Mac OS X Appearance panel text smoothing setting when rendering text, disabled by default
 pref("gfx.use_text_smoothing_setting", false);
 
 // Number of characters to consider emphasizing for rich autocomplete results
 pref("toolkit.autocomplete.richBoundaryCutoff", 200);
 
-// Variable controlling logging for osfile.
-pref("toolkit.osfile.log", false);
-
 pref("toolkit.scrollbox.smoothScroll", true);
 pref("toolkit.scrollbox.scrollIncrement", 20);
 pref("toolkit.scrollbox.clickToScroll.scrollDelay", 150);
 
 // Controls logging for Sqlite.sys.mjs.
 pref("toolkit.sqlitejsm.loglevel", "Error");
 
 pref("toolkit.tabbox.switchByScrolling", false);

--- a/testing/runtimes/manifest-runtimes-android.json
+++ b/testing/runtimes/manifest-runtimes-android.json
@@ -1559,17 +1559,16 @@
     "toolkit/components/autocomplete/tests/unit/xpcshell.ini": 12.66,
     "toolkit/components/captivedetect/test/unit/xpcshell.ini": 6.15,
     "toolkit/components/cascade_bloom_filter/test/xpcshell/xpcshell.ini": 0.54,
     "toolkit/components/contextualidentity/tests/unit/xpcshell.ini": 1.87,
     "toolkit/components/extensions/test/xpcshell/xpcshell-remote.ini": 0.85,
     "toolkit/components/extensions/test/xpcshell/xpcshell.ini": 19.12,
     "toolkit/components/featuregates/test/unit/xpcshell.ini": 1.71,
     "toolkit/components/mozintl/test/xpcshell.ini": 1.82,
-    "toolkit/components/osfile/tests/xpcshell/xpcshell.ini": 27.1,
     "toolkit/components/telemetry/tests/unit/xpcshell.ini": 42.36,
     "toolkit/components/timermanager/tests/unit/xpcshell.ini": 9.07,
     "toolkit/components/utils/test/unit/xpcshell.ini": 2.22,
     "toolkit/components/windowcreator/tests/unit/xpcshell.ini": 1.15,
     "toolkit/content/tests/unit/xpcshell.ini": 0.53,
     "toolkit/modules/tests/xpcshell/xpcshell.ini": 28.47,
     "toolkit/mozapps/downloads/tests/unit/xpcshell.ini": 2.41,
     "uriloader/exthandler/tests/unit/xpcshell.ini": 5.05,

--- a/testing/runtimes/manifest-runtimes-unix.json
+++ b/testing/runtimes/manifest-runtimes-unix.json
@@ -381,17 +381,16 @@
     "layout/xul/test/chrome.ini": 13.96,
     "security/manager/ssl/tests/mochitest/stricttransportsecurity/chrome.ini": 4.78,
     "services/fxaccounts/tests/mochitest/chrome.ini": 1.3,
     "testing/mochitest/chrome/chrome.ini": 2.22,
     "toolkit/components/aboutmemory/tests/chrome.ini": 23.09,
     "toolkit/components/certviewer/tests/chrome/chrome.ini": 2.78,
     "toolkit/components/ctypes/tests/chrome/chrome.ini": 1.4,
     "toolkit/components/extensions/test/mochitest/chrome.ini": 11.29,
-    "toolkit/components/osfile/tests/mochi/chrome.ini": 9.12,
     "toolkit/components/places/tests/chrome/chrome.ini": 1.87,
     "toolkit/components/prompts/test/chrome.ini": 106.31,
     "toolkit/components/resistfingerprinting/tests/chrome.ini": 3.99,
     "toolkit/components/url-classifier/tests/mochitest/chrome.ini": 35.15,
     "toolkit/components/viewsource/test/chrome.ini": 1.14,
     "toolkit/components/windowcreator/test/chrome.ini": 1.54,
     "toolkit/components/windowwatcher/test/chrome.ini": 1.32,
     "toolkit/components/workerloader/tests/chrome.ini": 1.19,

--- a/testing/runtimes/manifest-runtimes-windows.json
+++ b/testing/runtimes/manifest-runtimes-windows.json
@@ -383,17 +383,16 @@
     "layout/xul/test/chrome.ini": 12.69,
     "security/manager/ssl/tests/mochitest/stricttransportsecurity/chrome.ini": 3.14,
     "services/fxaccounts/tests/mochitest/chrome.ini": 1.37,
     "testing/mochitest/chrome/chrome.ini": 2.22,
     "toolkit/components/aboutmemory/tests/chrome.ini": 24.16,
     "toolkit/components/certviewer/tests/chrome/chrome.ini": 2.35,
     "toolkit/components/ctypes/tests/chrome/chrome.ini": 1.38,
     "toolkit/components/extensions/test/mochitest/chrome.ini": 8.63,
-    "toolkit/components/osfile/tests/mochi/chrome.ini": 7.73,
     "toolkit/components/places/tests/chrome/chrome.ini": 1.89,
     "toolkit/components/prompts/test/chrome.ini": 41.2,
     "toolkit/components/resistfingerprinting/tests/chrome.ini": 3.59,
     "toolkit/components/url-classifier/tests/mochitest/chrome.ini": 22.42,
     "toolkit/components/viewsource/test/chrome.ini": 1.14,
     "toolkit/components/windowcreator/test/chrome.ini": 1.51,
     "toolkit/components/windowwatcher/test/chrome.ini": 1.56,
     "toolkit/components/workerloader/tests/chrome.ini": 1.21,

--- a/toolkit/components/build/components.conf
+++ b/toolkit/components/build/components.conf
@@ -70,22 +70,16 @@ Classes = [
         'cid': '{91fa9e67-1427-4ee9-8ee0-1a6ed578bee1}',
         'contract_ids': ['@mozilla.org/reputationservice/login-reputation-service;1'],
         'singleton': True,
         'type': 'mozilla::LoginReputationService',
         'headers': ['/toolkit/components/reputationservice/LoginReputation.h'],
         'constructor': 'mozilla::LoginReputationService::GetSingleton',
     },
     {
-        'cid': '{63a69303-8a64-45a9-848c-d4e2792794e6}',
-        'contract_ids': ['@mozilla.org/toolkit/osfile/native-internals;1'],
-        'type': 'mozilla::NativeOSFileInternalsService',
-        'headers': ['mozilla/NativeOSFileInternals.h'],
-    },
-    {
         'name': 'Alerts',
         'cid': '{a0ccaaf8-09da-44d8-b250-9ac3e93c8117}',
         'contract_ids': ['@mozilla.org/alerts-service;1'],
         'type': 'nsAlertsService',
         'headers': ['/toolkit/components/alerts/nsAlertsService.h'],
         'overridable': True,
     },
     {

deleted file mode 100644
--- a/toolkit/components/lz4/lz4.cpp
+++ /dev/null
@@ -1,66 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include "mozilla/Compression.h"
-
-/**
- * LZ4 is a very fast byte-wise compression algorithm.
- *
- * Compared to Google's Snappy it is faster to compress and decompress and
- * generally produces output of about the same size.
- *
- * Compared to zlib it compresses at about 10x the speed, decompresses at about
- * 4x the speed and produces output of about 1.5x the size.
- *
- */
-
-using namespace mozilla::Compression;
-
-/**
- * Compresses 'inputSize' bytes from 'source' into 'dest'.
- * Destination buffer must be already allocated,
- * and must be sized to handle worst cases situations (input data not
- * compressible) Worst case size evaluation is provided by function
- * LZ4_compressBound()
- *
- * @param inputSize is the input size. Max supported value is ~1.9GB
- * @param return the number of bytes written in buffer dest
- */
-extern "C" MOZ_EXPORT size_t workerlz4_compress(const char* source,
-                                                size_t inputSize, char* dest) {
-  return LZ4::compress(source, inputSize, dest);
-}
-
-/**
- * If the source stream is malformed, the function will stop decoding
- * and return a negative result, indicating the byte position of the
- * faulty instruction
- *
- * This function never writes outside of provided buffers, and never
- * modifies input buffer.
- *
- * note : destination buffer must be already allocated.
- *        its size must be a minimum of 'outputSize' bytes.
- * @param outputSize is the output size, therefore the original size
- * @return true/false
- */
-extern "C" MOZ_EXPORT int workerlz4_decompress(const char* source,
-                                               size_t inputSize, char* dest,
-                                               size_t maxOutputSize,
-                                               size_t* bytesOutput) {
-  return LZ4::decompress(source, inputSize, dest, maxOutputSize, bytesOutput);
-}
-
-/*
-  Provides the maximum size that LZ4 may output in a "worst case"
-  scenario (input data not compressible) primarily useful for memory
-  allocation of output buffer.
-  note : this function is limited by "int" range (2^31-1)
-
-  @param inputSize is the input size. Max supported value is ~1.9GB
-  @return maximum output size in a "worst case" scenario
-*/
-extern "C" MOZ_EXPORT size_t workerlz4_maxCompressedSize(size_t inputSize) {
-  return LZ4::maxCompressedSize(inputSize);
-}

deleted file mode 100644
--- a/toolkit/components/lz4/lz4.js
+++ /dev/null
@@ -1,188 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-"use strict";
-
-var SharedAll;
-if (typeof Components != "undefined") {
-  SharedAll = ChromeUtils.import(
-    "resource://gre/modules/osfile/osfile_shared_allthreads.jsm"
-  );
-  var { Primitives } = ChromeUtils.import(
-    "resource://gre/modules/lz4_internal.js"
-  );
-  var { ctypes } = ChromeUtils.importESModule(
-    "resource://gre/modules/ctypes.sys.mjs"
-  );
-
-  this.EXPORTED_SYMBOLS = ["Lz4"];
-  this.exports = {};
-} else if (typeof module != "undefined" && typeof require != "undefined") {
-  /* eslint-env commonjs */
-  SharedAll = require("resource://gre/modules/osfile/osfile_shared_allthreads.jsm");
-  Primitives = require("resource://gre/modules/lz4_internal.js");
-  ctypes = self.ctypes;
-} else {
-  throw new Error(
-    "Please load this module with Component.utils.import or with require()"
-  );
-}
-
-const MAGIC_NUMBER = new Uint8Array([109, 111, 122, 76, 122, 52, 48, 0]); // "mozLz40\0"
-
-const BYTES_IN_SIZE_HEADER = ctypes.uint32_t.size;
-
-const HEADER_SIZE = MAGIC_NUMBER.byteLength + BYTES_IN_SIZE_HEADER;
-
-/**
- * An error during (de)compression
- *
- * @param {string} operation The name of the operation ("compress", "decompress")
- * @param {string} reason A reason to be used when matching errors. Must start
- * with "because", e.g. "becauseInvalidContent".
- * @param {string} message A human-readable message.
- */
-function LZError(operation, reason, message) {
-  SharedAll.OSError.call(this);
-  this.operation = operation;
-  this[reason] = true;
-  this.message = message;
-}
-LZError.prototype = Object.create(SharedAll.OSError);
-LZError.prototype.toString = function toString() {
-  return this.message;
-};
-exports.Error = LZError;
-
-/**
- * Compress a block to a form suitable for writing to disk.
- *
- * Compatibility note: For the moment, we are basing our code on lz4
- * 1.3, which does not specify a *file* format. Therefore, we define
- * our own format. Once lz4 defines a complete file format, we will
- * migrate both |compressFileContent| and |decompressFileContent| to this file
- * format. For backwards-compatibility, |decompressFileContent| will however
- * keep the ability to decompress files provided with older versions of
- * |compressFileContent|.
- *
- * Compressed files have the following layout:
- *
- * | MAGIC_NUMBER (8 bytes) | content size (uint32_t, little endian) | content, as obtained from lz4_compress |
- *
- * @param {TypedArray|void*} buffer The buffer to write to the disk.
- * @param {object=} options An object that may contain the following fields:
- *  - {number} bytes The number of bytes to read from |buffer|. If |buffer|
- *    is an |ArrayBuffer|, |bytes| defaults to |buffer.byteLength|. If
- *    |buffer| is a |void*|, |bytes| MUST be provided.
- * @return {Uint8Array} An array of bytes suitable for being written to the
- * disk.
- */
-function compressFileContent(array, options = {}) {
-  // Prepare the output array
-  let inputBytes;
-  if (SharedAll.isTypedArray(array) && !(options && "bytes" in options)) {
-    inputBytes = array.byteLength;
-  } else if (options && options.bytes) {
-    inputBytes = options.bytes;
-  } else {
-    throw new TypeError("compressFileContent requires a size");
-  }
-  let maxCompressedSize = Primitives.maxCompressedSize(inputBytes);
-  let outputArray = new Uint8Array(HEADER_SIZE + maxCompressedSize);
-
-  // Compress to output array
-  let payload = new Uint8Array(
-    outputArray.buffer,
-    outputArray.byteOffset + HEADER_SIZE
-  );
-  let compressedSize = Primitives.compress(array, inputBytes, payload);
-
-  // Add headers
-  outputArray.set(MAGIC_NUMBER);
-  let view = new DataView(outputArray.buffer);
-  view.setUint32(MAGIC_NUMBER.byteLength, inputBytes, true);
-
-  return new Uint8Array(outputArray.buffer, 0, HEADER_SIZE + compressedSize);
-}
-exports.compressFileContent = compressFileContent;
-
-function decompressFileContent(array, options = {}) {
-  let bytes = SharedAll.normalizeBufferArgs(array, options.bytes || null);
-  if (bytes < HEADER_SIZE) {
-    throw new LZError(
-      "decompress",
-      "becauseLZNoHeader",
-      `Buffer is too short (no header) - Data: ${options.path || array}`
-    );
-  }
-
-  // Read headers
-  let expectMagicNumber = new DataView(
-    array.buffer,
-    0,
-    MAGIC_NUMBER.byteLength
-  );
-  for (let i = 0; i < MAGIC_NUMBER.byteLength; ++i) {
-    if (expectMagicNumber.getUint8(i) != MAGIC_NUMBER[i]) {
-      throw new LZError(
-        "decompress",
-        "becauseLZWrongMagicNumber",
-        `Invalid header (no magic number) - Data: ${options.path || array}`
-      );
-    }
-  }
-
-  let sizeBuf = new DataView(
-    array.buffer,
-    MAGIC_NUMBER.byteLength,
-    BYTES_IN_SIZE_HEADER
-  );
-  let expectDecompressedSize =
-    sizeBuf.getUint8(0) +
-    (sizeBuf.getUint8(1) << 8) +
-    (sizeBuf.getUint8(2) << 16) +
-    (sizeBuf.getUint8(3) << 24);
-  if (expectDecompressedSize == 0) {
-    // The underlying algorithm cannot handle a size of 0
-    return new Uint8Array(0);
-  }
-
-  // Prepare the input buffer
-  let inputData = new DataView(array.buffer, HEADER_SIZE);
-
-  // Prepare the output buffer
-  let outputBuffer = new Uint8Array(expectDecompressedSize);
-  let decompressedBytes = new SharedAll.Type.size_t.implementation(0);
-
-  // Decompress
-  let success = Primitives.decompress(
-    inputData,
-    bytes - HEADER_SIZE,
-    outputBuffer,
-    outputBuffer.byteLength,
-    decompressedBytes.address()
-  );
-  if (!success) {
-    throw new LZError(
-      "decompress",
-      "becauseLZInvalidContent",
-      `Invalid content: Decompression stopped at ${
-        decompressedBytes.value
-      } - Data: ${options.path || array}`
-    );
-  }
-  return new Uint8Array(
-    outputBuffer.buffer,
-    outputBuffer.byteOffset,
-    decompressedBytes.value
-  );
-}
-exports.decompressFileContent = decompressFileContent;
-
-if (typeof Components != "undefined") {
-  this.Lz4 = {
-    compressFileContent,
-    decompressFileContent,
-  };
-}

deleted file mode 100644
--- a/toolkit/components/lz4/lz4_internal.js
+++ /dev/null
@@ -1,76 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-/* eslint-env commonjs */
-
-"use strict";
-
-var Primitives = {};
-
-var SharedAll;
-if (typeof Components != "undefined") {
-  SharedAll = ChromeUtils.import(
-    "resource://gre/modules/osfile/osfile_shared_allthreads.jsm"
-  );
-
-  this.EXPORTED_SYMBOLS = ["Primitives"];
-  this.Primitives = Primitives;
-  this.exports = {};
-} else if (typeof module != "undefined" && typeof require != "undefined") {
-  SharedAll = require("resource://gre/modules/osfile/osfile_shared_allthreads.jsm");
-} else {
-  throw new Error(
-    "Please load this module with Component.utils.import or with require()"
-  );
-}
-
-var libxul = new SharedAll.Library("libxul", SharedAll.Constants.Path.libxul);
-var Type = SharedAll.Type;
-
-libxul.declareLazyFFI(
-  Primitives,
-  "compress",
-  "workerlz4_compress",
-  null,
-  /* return*/ Type.size_t,
-  /* const source*/ Type.void_t.in_ptr,
-  /* inputSize*/ Type.size_t,
-  /* dest*/ Type.void_t.out_ptr
-);
-
-libxul.declareLazyFFI(
-  Primitives,
-  "decompress",
-  "workerlz4_decompress",
-  null,
-  /* return*/ Type.int,
-  /* const source*/ Type.void_t.in_ptr,
-  /* inputSize*/ Type.size_t,
-  /* dest*/ Type.void_t.out_ptr,
-  /* maxOutputSize*/ Type.size_t,
-  /* actualOutputSize*/ Type.size_t.out_ptr
-);
-
-libxul.declareLazyFFI(
-  Primitives,
-  "maxCompressedSize",
-  "workerlz4_maxCompressedSize",
-  null,
-  /* return*/ Type.size_t,
-  /* inputSize*/ Type.size_t
-);
-
-if (typeof module != "undefined") {
-  module.exports = {
-    get compress() {
-      return Primitives.compress;
-    },
-    get decompress() {
-      return Primitives.decompress;
-    },
-    get maxCompressedSize() {
-      return Primitives.maxCompressedSize;
-    },
-  };
-}

deleted file mode 100644
--- a/toolkit/components/lz4/moz.build
+++ /dev/null
@@ -1,21 +0,0 @@
-# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
-# vim: set filetype=python:
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at http://mozilla.org/MPL/2.0/.
-
-with Files("**"):
-    BUG_COMPONENT = ("Toolkit", "OS.File")
-
-XPCSHELL_TESTS_MANIFESTS += ["tests/xpcshell/xpcshell.ini"]
-
-EXTRA_JS_MODULES += [
-    "lz4.js",
-    "lz4_internal.js",
-]
-
-SOURCES += [
-    "lz4.cpp",
-]
-
-FINAL_LIBRARY = "xul"

deleted file mode 100644
--- a/toolkit/components/lz4/tests/xpcshell/data/chrome.manifest
+++ /dev/null
@@ -1,1 +0,0 @@
-content test_lz4 ./

deleted file mode 100644
index a354edc03673f2d3fc3b9f07f9f39d1bd59bf656..0000000000000000000000000000000000000000
GIT binary patch
literal 0
Hc$@<O00001

deleted file mode 100644
--- a/toolkit/components/lz4/tests/xpcshell/data/worker_lz4.js
+++ /dev/null
@@ -1,166 +0,0 @@
-/* eslint-env mozilla/chrome-worker */
-
-/* import-globals-from /toolkit/components/workerloader/require.js */
-importScripts("resource://gre/modules/workers/require.js");
-/* import-globals-from /toolkit/components/osfile/osfile.jsm */
-importScripts("resource://gre/modules/osfile.jsm");
-
-function info(x) {
-  // self.postMessage({kind: "do_print", args: [x]});
-  dump("TEST-INFO: " + x + "\n");
-}
-
-const Assert = {
-  ok(x) {
-    self.postMessage({ kind: "assert_ok", args: [!!x] });
-    if (x) {
-      dump("TEST-PASS: " + x + "\n");
-    } else {
-      throw new Error("Assert.ok failed");
-    }
-  },
-
-  equal(a, b) {
-    let result = a == b;
-    self.postMessage({ kind: "assert_ok", args: [result] });
-    if (!result) {
-      throw new Error("Assert.equal failed " + a + " != " + b);
-    }
-  },
-};
-
-function do_test_complete() {
-  self.postMessage({ kind: "do_test_complete", args: [] });
-}
-
-self.onmessage = function() {
-  try {
-    run_test();
-  } catch (ex) {
-    let { message, moduleStack, moduleName, lineNumber } = ex;
-    let error = new Error(message, moduleName, lineNumber);
-    error.stack = moduleStack;
-    dump("Uncaught error: " + error + "\n");
-    dump("Full stack: " + moduleStack + "\n");
-    throw error;
-  }
-};
-
-var Lz4;
-var Internals;
-function test_import() {
-  Lz4 = require("resource://gre/modules/lz4.js");
-  Internals = require("resource://gre/modules/lz4_internal.js");
-}
-
-function test_bound() {
-  for (let k of ["compress", "decompress", "maxCompressedSize"]) {
-    try {
-      info("Checking the existence of " + k + "\n");
-      Assert.ok(!!Internals[k]);
-      info(k + " exists");
-    } catch (ex) {
-      // Ignore errors
-      info(k + " doesn't exist!");
-    }
-  }
-}
-
-function test_reference_file() {
-  info("Decompress reference file");
-  let path = OS.Path.join("data", "compression.lz");
-  let data = OS.File.read(path);
-  let decompressed = Lz4.decompressFileContent(data);
-  let text = new TextDecoder().decode(decompressed);
-  Assert.equal(text, "Hello, lz4");
-}
-
-function compare_arrays(a, b) {
-  return Array.prototype.join.call(a) == Array.prototype.join.call(b);
-}
-
-function run_rawcompression(name, array) {
-  info("Raw compression test " + name);
-  let length = array.byteLength;
-  let compressedArray = new Uint8Array(Internals.maxCompressedSize(length));
-  let compressedBytes = Internals.compress(array, length, compressedArray);
-  compressedArray = new Uint8Array(compressedArray.buffer, 0, compressedBytes);
-  info("Raw compressed: " + length + " into " + compressedBytes);
-
-  let decompressedArray = new Uint8Array(length);
-  let decompressedBytes = new ctypes.size_t();
-  let success = Internals.decompress(
-    compressedArray,
-    compressedBytes,
-    decompressedArray,
-    length,
-    decompressedBytes.address()
-  );
-  info("Raw decompression success? " + success);
-  info("Raw decompression size: " + decompressedBytes.value);
-  Assert.ok(compare_arrays(array, decompressedArray));
-}
-
-function run_filecompression(name, array) {
-  info("File compression test " + name);
-  let compressed = Lz4.compressFileContent(array);
-  info(
-    "Compressed " + array.byteLength + " bytes into " + compressed.byteLength
-  );
-
-  let decompressed = Lz4.decompressFileContent(compressed);
-  info(
-    "Decompressed " +
-      compressed.byteLength +
-      " bytes into " +
-      decompressed.byteLength
-  );
-  Assert.ok(compare_arrays(array, decompressed));
-}
-
-function run_faileddecompression(name, array) {
-  info("invalid decompression test " + name);
-
-  // Ensure that raw decompression doesn't segfault
-  let length = 1 << 14;
-  let decompressedArray = new Uint8Array(length);
-  let decompressedBytes = new ctypes.size_t();
-  Internals.decompress(
-    array,
-    array.byteLength,
-    decompressedArray,
-    length,
-    decompressedBytes.address()
-  );
-
-  // File decompression should fail with an acceptable exception
-  let exn = null;
-  try {
-    Lz4.decompressFileContent(array);
-  } catch (ex) {
-    exn = ex;
-  }
-  Assert.ok(exn);
-  if (array.byteLength < 10) {
-    Assert.ok(exn.becauseLZNoHeader);
-  } else {
-    Assert.ok(exn.becauseLZWrongMagicNumber);
-  }
-}
-
-function run_test() {
-  test_import();
-  test_bound();
-  test_reference_file();
-  for (let length of [0, 1, 1024]) {
-    let array = new Uint8Array(length);
-    for (let i = 0; i < length; ++i) {
-      array[i] = i % 256;
-    }
-    let name = length + " bytes";
-    run_rawcompression(name, array);
-    run_filecompression(name, array);
-    run_faileddecompression(name, array);
-  }
-  do_test_complete();
-}

deleted file mode 100644
--- a/toolkit/components/lz4/tests/xpcshell/test_lz4.js
+++ /dev/null
@@ -1,35 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
-   http://creativecommons.org/publicdomain/zero/1.0/ */
-
-var WORKER_SOURCE_URI = "chrome://test_lz4/content/worker_lz4.js";
-do_load_manifest("data/chrome.manifest");
-
-add_task(function() {
-  let worker = new ChromeWorker(WORKER_SOURCE_URI);
-  return new Promise((resolve, reject) => {
-    worker.onmessage = function(event) {
-      let data = event.data;
-      switch (data.kind) {
-        case "assert_ok":
-          try {
-            Assert.ok(data.args[0]);
-          } catch (ex) {
-            // Ignore errors
-          }
-          return;
-        case "do_test_complete":
-          resolve();
-          worker.terminate();
-          break;
-        case "do_print":
-          info(data.args[0]);
-      }
-    };
-    worker.onerror = function(event) {
-      let error = new Error(event.message, event.filename, event.lineno);
-      worker.terminate();
-      reject(error);
-    };
-    worker.postMessage("START");
-  });
-});

deleted file mode 100644
--- a/toolkit/components/lz4/tests/xpcshell/test_lz4_sync.js
+++ /dev/null
@@ -1,41 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
-   http://creativecommons.org/publicdomain/zero/1.0/ */
-
-const { Lz4 } = ChromeUtils.import("resource://gre/modules/lz4.js");
-const { OS } = ChromeUtils.import("resource://gre/modules/osfile.jsm");
-
-function compare_arrays(a, b) {
-  return Array.prototype.join.call(a) == Array.prototype.join.call(b);
-}
-
-add_task(async function() {
-  let path = OS.Path.join("data", "compression.lz");
-  let data = await OS.File.read(path);
-  let decompressed = Lz4.decompressFileContent(data);
-  let text = new TextDecoder().decode(decompressed);
-  Assert.equal(text, "Hello, lz4");
-});
-
-add_task(async function() {
-  for (let length of [0, 1, 1024]) {
-    let array = new Uint8Array(length);
-    for (let i = 0; i < length; ++i) {
-      array[i] = i % 256;
-    }
-
-    let compressed = Lz4.compressFileContent(array);
-    info(
-      "Compressed " + array.byteLength + " bytes into " + compressed.byteLength
-    );
-
-    let decompressed = Lz4.decompressFileContent(compressed);
-    info(
-      "Decompressed " +
-        compressed.byteLength +
-        " bytes into " +
-        decompressed.byteLength
-    );
-
-    Assert.ok(compare_arrays(array, decompressed));
-  }
-});

deleted file mode 100644
--- a/toolkit/components/lz4/tests/xpcshell/xpcshell.ini
+++ /dev/null
@@ -1,10 +0,0 @@
-[DEFAULT]
-head =
-skip-if = toolkit == 'android'
-support-files =
-  data/worker_lz4.js
-  data/chrome.manifest
-  data/compression.lz
-
-[test_lz4.js]
-[test_lz4_sync.js]

--- a/toolkit/components/moz.build
+++ b/toolkit/components/moz.build
@@ -41,21 +41,19 @@ DIRS += [
     "formautofill",
     "finalizationwitness",
     "find",
     "forgetaboutsite",
     "glean",
     "httpsonlyerror",
     "jsoncpp/src/lib_json",
     "kvstore",
-    "lz4",
     "mediasniffer",
     "mozintl",
     "mozprotocol",
-    "osfile",
     "parentalcontrols",
     "passwordmgr",
     "pdfjs",
     "perfmonitoring",
     "pictureinpicture",
     "places",
     "processtools",
     "processsingleton",

deleted file mode 100644
--- a/toolkit/components/osfile/NativeOSFileInternals.cpp
+++ /dev/null
@@ -1,1263 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set ts=8 sts=2 et sw=2 tw=80: */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-/**
- * Native implementation of some OS.File operations.
- */
-
-#include "NativeOSFileInternals.h"
-
-#include "nsString.h"
-#include "nsNetCID.h"
-#include "nsThreadUtils.h"
-#include "nsCycleCollectionParticipant.h"
-#include "nsServiceManagerUtils.h"
-#include "nsProxyRelease.h"
-
-#include "mozilla/dom/NativeOSFileInternalsBinding.h"
-
-#include "mozilla/Encoding.h"
-#include "nsIEventTarget.h"
-
-#include "mozilla/DebugOnly.h"
-#include "mozilla/Scoped.h"
-#include "mozilla/HoldDropJSObjects.h"
-#include "mozilla/TimeStamp.h"
-#include "mozilla/UniquePtr.h"
-
-#include "prio.h"
-#include "prerror.h"
-#include "private/pprio.h"
-
-#include "jsapi.h"
-#include "jsfriendapi.h"
-#include "js/ArrayBuffer.h"  // JS::GetArrayBufferByteLength,IsArrayBufferObject,NewArrayBufferWithContents,StealArrayBufferContents
-#include "js/experimental/TypedData.h"  // JS_NewUint8ArrayWithBuffer
-#include "js/Utility.h"
-#include "xpcpublic.h"
-
-#include <algorithm>
-#if defined(XP_UNIX)
-#  include <errno.h>
-#endif  // defined (XP_UNIX)
-
-#if defined(XP_WIN)
-#  include <windows.h>
-#endif  // defined (XP_WIN)
-
-namespace mozilla {
-
-MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLATE(ScopedPRFileDesc, PRFileDesc,
-                                          PR_Close)
-
-namespace {
-
-// Utilities for safely manipulating ArrayBuffer contents even in the
-// absence of a JSContext.
-
-/**
- * The C buffer underlying to an ArrayBuffer. Throughout the code, we manipulate
- * this instead of a void* buffer, as this lets us transfer data across threads
- * and into JavaScript without copy.
- */
-struct ArrayBufferContents {
-  /**
-   * The data of the ArrayBuffer. This is the pointer manipulated to
-   * read/write the contents of the buffer.
-   */
-  uint8_t* data;
-  /**
-   * The number of bytes in the ArrayBuffer.
-   */
-  size_t nbytes;
-};
-
-/**
- * RAII for ArrayBufferContents.
- */
-struct ScopedArrayBufferContentsTraits {
-  typedef ArrayBufferContents type;
-  const static type empty() {
-    type result = {0, 0};
-    return result;
-  }
-  static void release(type ptr) {
-    js_free(ptr.data);
-    ptr.data = nullptr;
-    ptr.nbytes = 0;
-  }
-};
-
-struct MOZ_NON_TEMPORARY_CLASS ScopedArrayBufferContents
-    : public Scoped<ScopedArrayBufferContentsTraits> {
-  explicit ScopedArrayBufferContents()
-      : Scoped<ScopedArrayBufferContentsTraits>() {}
-
-  ScopedArrayBufferContents& operator=(ArrayBufferContents ptr) {
-    Scoped<ScopedArrayBufferContentsTraits>::operator=(ptr);
-    return *this;
-  }
-
-  /**
-   * Request memory for this ArrayBufferContent. This memory may later
-   * be used to create an ArrayBuffer object (possibly on another
-   * thread) without copy.
-   *
-   * @return true In case of success, false otherwise.
-   */
-  bool Allocate(uint32_t length) {
-    dispose();
-    ArrayBufferContents& value = rwget();
-    void* ptr = js_calloc(1, length);
-    if (ptr) {
-      value.data = (uint8_t*)ptr;
-      value.nbytes = length;
-      return true;
-    }
-    return false;
-  }
-
- private:
-  explicit ScopedArrayBufferContents(ScopedArrayBufferContents& source) =
-      delete;
-  ScopedArrayBufferContents& operator=(ScopedArrayBufferContents& source) =
-      delete;
-};
-
-///////// Cross-platform issues
-
-// Platform specific constants. As OS.File always uses OS-level
-// errors, we need to map a few high-level errors to OS-level
-// constants.
-#if defined(XP_UNIX)
-#  define OS_ERROR_FILE_EXISTS EEXIST
-#  define OS_ERROR_NOMEM ENOMEM
-#  define OS_ERROR_INVAL EINVAL
-#  define OS_ERROR_TOO_LARGE EFBIG
-#  define OS_ERROR_RACE EIO
-#elif defined(XP_WIN)
-#  define OS_ERROR_FILE_EXISTS ERROR_ALREADY_EXISTS
-#  define OS_ERROR_NOMEM ERROR_NOT_ENOUGH_MEMORY
-#  define OS_ERROR_INVAL ERROR_BAD_ARGUMENTS
-#  define OS_ERROR_TOO_LARGE ERROR_FILE_TOO_LARGE
-#  define OS_ERROR_RACE ERROR_SHARING_VIOLATION
-#else
-#  error "We do not have platform-specific constants for this platform"
-#endif
-
-///////// Results of OS.File operations
-
-/**
- * Base class for results passed to the callbacks.
- *
- * This base class implements caching of JS values returned to the client.
- * We make use of this caching in derived classes e.g. to avoid accidents
- * when we transfer data allocated on another thread into JS. Note that
- * this caching can lead to cycles (e.g. if a client adds a back-reference
- * in the JS value), so we implement all Cycle Collector primitives in
- * AbstractResult.
- */
-class AbstractResult : public nsINativeOSFileResult {
- public:
-  NS_DECL_NSINATIVEOSFILERESULT
-  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
-  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(AbstractResult)
-
-  /**
-   * Construct the result object. Must be called on the main thread
-   * as the AbstractResult is cycle-collected.
-   *
-   * @param aStartDate The instant at which the operation was
-   * requested.  Used to collect Telemetry statistics.
-   */
-  explicit AbstractResult(TimeStamp aStartDate) : mStartDate(aStartDate) {
-    MOZ_ASSERT(NS_IsMainThread());
-    mozilla::HoldJSObjects(this);
-  }
-
-  /**
-   * Setup the AbstractResult once data is available.
-   *
-   * @param aDispatchDate The instant at which the IO thread received
-   * the operation request. Used to collect Telemetry statistics.
-   * @param aExecutionDuration The duration of the operation on the
-   * IO thread.
-   */
-  void Init(TimeStamp aDispatchDate, TimeDuration aExecutionDuration) {
-    MOZ_ASSERT(!NS_IsMainThread());
-
-    mDispatchDuration = (aDispatchDate - mStartDate);
-    mExecutionDuration = aExecutionDuration;
-  }
-
-  /**
-   * Drop any data that could lead to a cycle.
-   */
-  void DropJSData() { mCachedResult = JS::UndefinedValue(); }
-
- protected:
-  virtual ~AbstractResult() {
-    MOZ_ASSERT(NS_IsMainThread());
-    mozilla::DropJSObjects(this);
-  }
-
-  virtual nsresult GetCacheableResult(JSContext* cx,
-                                      JS::MutableHandle<JS::Value> aResult) = 0;
-
- private:
-  TimeStamp mStartDate;
-  TimeDuration mDispatchDuration;
-  TimeDuration mExecutionDuration;
-  JS::Heap<JS::Value> mCachedResult;
-};
-
-NS_IMPL_CYCLE_COLLECTING_ADDREF(AbstractResult)
-NS_IMPL_CYCLE_COLLECTING_RELEASE(AbstractResult)
-
-NS_IMPL_CYCLE_COLLECTION_CLASS(AbstractResult)
-
-NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(AbstractResult)
-  NS_INTERFACE_MAP_ENTRY(nsINativeOSFileResult)
-  NS_INTERFACE_MAP_ENTRY(nsISupports)
-NS_INTERFACE_MAP_END
-
-NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(AbstractResult)
-  NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mCachedResult)
-NS_IMPL_CYCLE_COLLECTION_TRACE_END
-
-NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(AbstractResult)
-NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
-
-NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(AbstractResult)
-  tmp->DropJSData();
-NS_IMPL_CYCLE_COLLECTION_UNLINK_END
-
-NS_IMETHODIMP
-AbstractResult::GetDispatchDurationMS(double* aDispatchDuration) {
-  *aDispatchDuration = mDispatchDuration.ToMilliseconds();
-  return NS_OK;
-}
-
-NS_IMETHODIMP
-AbstractResult::GetExecutionDurationMS(double* aExecutionDuration) {
-  *aExecutionDuration = mExecutionDuration.ToMilliseconds();
-  return NS_OK;
-}
-
-NS_IMETHODIMP
-AbstractResult::GetResult(JSContext* cx, JS::MutableHandle<JS::Value> aResult) {
-  if (mCachedResult.isUndefined()) {
-    nsresult rv = GetCacheableResult(cx, aResult);
-    if (NS_FAILED(rv)) {
-      return rv;
-    }
-    mCachedResult = aResult;
-    return NS_OK;
-  }
-  aResult.set(mCachedResult);
-  return NS_OK;
-}
-
-/**
- * Return a result as a string.
- *
- * In this implementation, attribute |result| is a string. Strings are
- * passed to JS without copy.
- */
-class StringResult final : public AbstractResult {
- public:
-  explicit StringResult(TimeStamp aStartDate) : AbstractResult(aStartDate) {}
-
-  /**
-   * Initialize the object once the contents of the result as available.
-   *
-   * @param aContents The string to pass to JavaScript. Ownership of the
-   * string and its contents is passed to StringResult. The string must
-   * be valid UTF-16.
-   */
-  void Init(TimeStamp aDispatchDate, TimeDuration aExecutionDuration,
-            nsString& aContents) {
-    AbstractResult::Init(aDispatchDate, aExecutionDuration);
-    mContents = aContents;
-  }
-
- protected:
-  nsresult GetCacheableResult(JSContext* cx,
-                              JS::MutableHandle<JS::Value> aResult) override;
-
- private:
-  nsString mContents;
-};
-
-nsresult StringResult::GetCacheableResult(
-    JSContext* cx, JS::MutableHandle<JS::Value> aResult) {
-  MOZ_ASSERT(NS_IsMainThread());
-  MOZ_ASSERT(mContents.get());
-
-  // Convert mContents to a js string without copy. Note that this
-  // may have the side-effect of stealing the contents of the string
-  // from XPCOM and into JS.
-  if (!xpc::StringToJsval(cx, mContents, aResult)) {
-    return NS_ERROR_FAILURE;
-  }
-  return NS_OK;
-}
-
-/**
- * Return a result as a Uint8Array.
- *
- * In this implementation, attribute |result| is a Uint8Array. The array
- * is passed to JS without memory copy.
- */
-class TypedArrayResult final : public AbstractResult {
- public:
-  explicit TypedArrayResult(TimeStamp aStartDate)
-      : AbstractResult(aStartDate) {}
-
-  /**
-   * @param aContents The contents to pass to JS. Calling this method.
-   * transmits ownership of the ArrayBufferContents to the TypedArrayResult.
-   * Do not reuse this value anywhere else.
-   */
-  void Init(TimeStamp aDispatchDate, TimeDuration aExecutionDuration,
-            ArrayBufferContents aContents) {
-    AbstractResult::Init(aDispatchDate, aExecutionDuration);
-    mContents = aContents;
-  }
-
- protected:
-  nsresult GetCacheableResult(JSContext* cx,
-                              JS::MutableHandle<JS::Value> aResult) override;
-
- private:
-  ScopedArrayBufferContents mContents;
-};
-
-nsresult TypedArrayResult::GetCacheableResult(
-    JSContext* cx, JS::MutableHandle<JS::Value> aResult) {
-  MOZ_ASSERT(NS_IsMainThread());
-  // We cannot simply construct a typed array using contents.data as
-  // this would allow us to have several otherwise unrelated
-  // ArrayBuffers with the same underlying C buffer. As this would be
-  // very unsafe, we need to cache the result once we have it.
-
-  const ArrayBufferContents& contents = mContents.get();
-  MOZ_ASSERT(contents.data);
-
-  // This takes ownership of the buffer and notes the memory allocation.
-  JS::Rooted<JSObject*> arrayBuffer(
-      cx, JS::NewArrayBufferWithContents(cx, contents.nbytes, contents.data));
-  if (!arrayBuffer) {
-    return NS_ERROR_OUT_OF_MEMORY;
-  }
-
-  JS::Rooted<JSObject*> result(
-      cx, JS_NewUint8ArrayWithBuffer(cx, arrayBuffer, 0, contents.nbytes));
-  if (!result) {
-    return NS_ERROR_OUT_OF_MEMORY;
-  }
-  mContents.forget();
-
-  aResult.setObject(*result);
-  return NS_OK;
-}
-
-/**
- * Return a result as an int32_t.
- *
- * In this implementation, attribute |result| is an int32_t.
- */
-class Int32Result final : public AbstractResult {
- public:
-  explicit Int32Result(TimeStamp aStartDate)
-      : AbstractResult(aStartDate), mContents(0) {}
-
-  /**
-   * Initialize the object once the contents of the result are available.
-   *
-   * @param aContents The contents to pass to JS. This is an int32_t.
-   */
-  void Init(TimeStamp aDispatchDate, TimeDuration aExecutionDuration,
-            int32_t aContents) {
-    AbstractResult::Init(aDispatchDate, aExecutionDuration);
-    mContents = aContents;
-  }
-
- protected:
-  nsresult GetCacheableResult(JSContext* cx,
-                              JS::MutableHandle<JS::Value> aResult) override;
-
- private:
-  int32_t mContents;
-};
-
-nsresult Int32Result::GetCacheableResult(JSContext* cx,
-                                         JS::MutableHandle<JS::Value> aResult) {
-  MOZ_ASSERT(NS_IsMainThread());
-  aResult.set(JS::NumberValue(mContents));
-  return NS_OK;
-}
-
-//////// Callback events
-
-/**
- * An event used to notify asynchronously of an error.
- */
-class OSFileErrorEvent final : public Runnable {
- public:
-  /**
-   * @param aOnSuccess The success callback.
-   * @param aOnError The error callback.
-   * @param aDiscardedResult The discarded result.
-   * @param aOperation The name of the operation, used for error reporting.
-   * @param aOSError The OS error of the operation, as returned by errno/
-   * GetLastError().
-   *
-   * Note that we pass both the success callback and the error
-   * callback, as well as the discarded result to ensure that they are
-   * all released on the main thread, rather than on the IO thread
-   * (which would hopefully segfault). Also, we pass the callbacks as
-   * alread_AddRefed to ensure that we do not manipulate main-thread
-   * only refcounters off the main thread.
-   */
-  OSFileErrorEvent(
-      nsMainThreadPtrHandle<nsINativeOSFileSuccessCallback>& aOnSuccess,
-      nsMainThreadPtrHandle<nsINativeOSFileErrorCallback>& aOnError,
-      already_AddRefed<AbstractResult>& aDiscardedResult,
-      const nsACString& aOperation, int32_t aOSError)
-      : Runnable("OSFileErrorEvent"),
-        mOnSuccess(aOnSuccess),
-        mOnError(aOnError),
-        mDiscardedResult(aDiscardedResult),
-        mOSError(aOSError),
-        mOperation(aOperation) {
-    MOZ_ASSERT(!NS_IsMainThread());
-  }
-
-  NS_IMETHOD Run() override {
-    MOZ_ASSERT(NS_IsMainThread());
-    (void)mOnError->Complete(mOperation, mOSError);
-
-    // Ensure that the callbacks are released on the main thread.
-    mOnSuccess = nullptr;
-    mOnError = nullptr;
-    mDiscardedResult = nullptr;
-
-    return NS_OK;
-  }
-
- private:
-  // The callbacks. Maintained as nsMainThreadPtrHandle as they are generally
-  // xpconnect values, which cannot be manipulated with nsCOMPtr off
-  // the main thread. We store both the success callback and the
-  // error callback to ensure that they are safely released on the
-  // main thread.
-  nsMainThreadPtrHandle<nsINativeOSFileSuccessCallback> mOnSuccess;
-  nsMainThreadPtrHandle<nsINativeOSFileErrorCallback> mOnError;
-  RefPtr<AbstractResult> mDiscardedResult;
-  int32_t mOSError;
-  nsCString mOperation;
-};
-
-/**
- * An event used to notify of a success.
- */
-class SuccessEvent final : public Runnable {
- public:
-  /**
-   * @param aOnSuccess The success callback.
-   * @param aOnError The error callback.
-   *
-   * Note that we pass both the success callback and the error
-   * callback to ensure that they are both released on the main
-   * thread, rather than on the IO thread (which would hopefully
-   * segfault). Also, we pass them as alread_AddRefed to ensure that
-   * we do not manipulate xpconnect refcounters off the main thread
-   * (which is illegal).
-   */
-  SuccessEvent(
-      nsMainThreadPtrHandle<nsINativeOSFileSuccessCallback>& aOnSuccess,
-      nsMainThreadPtrHandle<nsINativeOSFileErrorCallback>& aOnError,
-      already_AddRefed<nsINativeOSFileResult>& aResult)
-      : Runnable("SuccessEvent"),
-        mOnSuccess(aOnSuccess),
-        mOnError(aOnError),
-        mResult(aResult) {
-    MOZ_ASSERT(!NS_IsMainThread());
-  }
-
-  NS_IMETHOD Run() override {
-    MOZ_ASSERT(NS_IsMainThread());
-    (void)mOnSuccess->Complete(mResult);
-
-    // Ensure that the callbacks are released on the main thread.
-    mOnSuccess = nullptr;
-    mOnError = nullptr;
-    mResult = nullptr;
-
-    return NS_OK;
-  }
-
- private:
-  // The callbacks. Maintained as nsMainThreadPtrHandle as they are generally
-  // xpconnect values, which cannot be manipulated with nsCOMPtr off
-  // the main thread. We store both the success callback and the
-  // error callback to ensure that they are safely released on the
-  // main thread.
-  nsMainThreadPtrHandle<nsINativeOSFileSuccessCallback> mOnSuccess;
-  nsMainThreadPtrHandle<nsINativeOSFileErrorCallback> mOnError;
-  RefPtr<nsINativeOSFileResult> mResult;
-};
-
-//////// Action events
-
-/**
- * Base class shared by actions.
- */
-class AbstractDoEvent : public Runnable {
- public:
-  AbstractDoEvent(
-      nsMainThreadPtrHandle<nsINativeOSFileSuccessCallback>& aOnSuccess,
-      nsMainThreadPtrHandle<nsINativeOSFileErrorCallback>& aOnError)
-      : Runnable("AbstractDoEvent"),
-        mOnSuccess(aOnSuccess),
-        mOnError(aOnError)
-#if defined(DEBUG)
-        ,
-        mResolved(false)
-#endif  // defined(DEBUG)
-  {
-    MOZ_ASSERT(NS_IsMainThread());
-  }
-
-  /**
-   * Fail, asynchronously.
-   */
-  void Fail(const nsACString& aOperation,
-            already_AddRefed<AbstractResult>&& aDiscardedResult,
-            int32_t aOSError = 0) {
-    Resolve();
-
-    RefPtr<OSFileErrorEvent> event = new OSFileErrorEvent(
-        mOnSuccess, mOnError, aDiscardedResult, aOperation, aOSError);
-    nsresult rv = NS_DispatchToMainThread(event);
-    if (NS_FAILED(rv)) {
-      // Last ditch attempt to release on the main thread - some of
-      // the members of event are not thread-safe, so letting the
-      // pointer go out of scope would cause a crash.
-      NS_ReleaseOnMainThread("AbstractDoEvent::OSFileErrorEvent",
-                             event.forget());
-    }
-  }
-
-  /**
-   * Succeed, asynchronously.
-   */
-  void Succeed(already_AddRefed<nsINativeOSFileResult>&& aResult) {
-    Resolve();
-    RefPtr<SuccessEvent> event =
-        new SuccessEvent(mOnSuccess, mOnError, aResult);
-    nsresult rv = NS_DispatchToMainThread(event);
-    if (NS_FAILED(rv)) {
-      // Last ditch attempt to release on the main thread - some of
-      // the members of event are not thread-safe, so letting the
-      // pointer go out of scope would cause a crash.
-      NS_ReleaseOnMainThread("AbstractDoEvent::SuccessEvent", event.forget());
-    }
-  }
-
- private:
-  /**
-   * Mark the event as complete, for debugging purposes.
-   */
-  void Resolve() {
-#if defined(DEBUG)
-    MOZ_ASSERT(!mResolved);
-    mResolved = true;
-#endif  // defined(DEBUG)
-  }
-
- private:
-  nsMainThreadPtrHandle<nsINativeOSFileSuccessCallback> mOnSuccess;
-  nsMainThreadPtrHandle<nsINativeOSFileErrorCallback> mOnError;
-#if defined(DEBUG)
-  // |true| once the action is complete
-  bool mResolved;
-#endif  // defined(DEBUG)
-};
-
-/**
- * An abstract event implementing reading from a file.
- *
- * Concrete subclasses are responsible for handling the
- * data obtained from the file and possibly post-processing it.
- */
-class AbstractReadEvent : public AbstractDoEvent {
- public:
-  /**
-   * @param aPath The path of the file.
-   */
-  AbstractReadEvent(
-      const nsAString& aPath, const uint64_t aBytes,
-      nsMainThreadPtrHandle<nsINativeOSFileSuccessCallback>& aOnSuccess,
-      nsMainThreadPtrHandle<nsINativeOSFileErrorCallback>& aOnError)
-      : AbstractDoEvent(aOnSuccess, aOnError), mPath(aPath), mBytes(aBytes) {
-    MOZ_ASSERT(NS_IsMainThread());
-  }
-
-  NS_IMETHOD Run() override {
-    MOZ_ASSERT(!NS_IsMainThread());
-    TimeStamp dispatchDate = TimeStamp::Now();
-
-    nsresult rv = BeforeRead();
-    if (NS_FAILED(rv)) {
-      // Error reporting is handled by BeforeRead();
-      return NS_OK;
-    }
-
-    ScopedArrayBufferContents buffer;
-    rv = Read(buffer);
-    if (NS_FAILED(rv)) {
-      // Error reporting is handled by Read();
-      return NS_OK;
-    }
-
-    AfterRead(dispatchDate, buffer);
-    return NS_OK;
-  }
-
- private:
-  /**
-   * Read synchronously.
-   *
-   * Must be called off the main thread.
-   *
-   * @param aBuffer The destination buffer.
-   */
-  nsresult Read(ScopedArrayBufferContents& aBuffer) {
-    MOZ_ASSERT(!NS_IsMainThread());
-
-    ScopedPRFileDesc file;
-#if defined(XP_WIN)
-    // On Windows, we can't use PR_OpenFile because it doesn't
-    // handle UTF-16 encoding, which is pretty bad. In addition,
-    // PR_OpenFile opens files without sharing, which is not the
-    // general semantics of OS.File.
-    HANDLE handle =
-        ::CreateFileW(mPath.get(), GENERIC_READ,
-                      FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
-                      /*Security attributes*/ nullptr, OPEN_EXISTING,
-                      FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN,
-                      /*Template file*/ nullptr);
-
-    if (handle == INVALID_HANDLE_VALUE) {
-      Fail("open"_ns, nullptr, ::GetLastError());
-      return NS_ERROR_FAILURE;
-    }
-
-    file = PR_ImportFile((PROsfd)handle);
-    if (!file) {
-      // |file| is closed by PR_ImportFile
-      Fail("ImportFile"_ns, nullptr, PR_GetOSError());
-      return NS_ERROR_FAILURE;
-    }
-
-#else
-    // On other platforms, PR_OpenFile will do.
-    NS_ConvertUTF16toUTF8 path(mPath);
-    file = PR_OpenFile(path.get(), PR_RDONLY, 0);
-    if (!file) {
-      Fail("open"_ns, nullptr, PR_GetOSError());
-      return NS_ERROR_FAILURE;
-    }
-
-#endif  // defined(XP_XIN)
-
-    PRFileInfo64 stat;
-    if (PR_GetOpenFileInfo64(file, &stat) != PR_SUCCESS) {
-      Fail("stat"_ns, nullptr, PR_GetOSError());
-      return NS_ERROR_FAILURE;
-    }
-
-    uint64_t bytes = std::min((uint64_t)stat.size, mBytes);
-    if (bytes > UINT32_MAX) {
-      Fail("Arithmetics"_ns, nullptr, OS_ERROR_INVAL);
-      return NS_ERROR_FAILURE;
-    }
-
-    if (!aBuffer.Allocate(bytes)) {
-      Fail("allocate"_ns, nullptr, OS_ERROR_NOMEM);
-      return NS_ERROR_FAILURE;
-    }
-
-    uint64_t total_read = 0;
-    int32_t just_read = 0;
-    char* dest_chars = reinterpret_cast<char*>(aBuffer.rwget().data);
-    do {
-      just_read = PR_Read(file, dest_chars + total_read,
-                          std::min(uint64_t(PR_INT32_MAX), bytes - total_read));
-      if (just_read == -1) {
-        Fail("read"_ns, nullptr, PR_GetOSError());
-        return NS_ERROR_FAILURE;
-      }
-      total_read += just_read;
-    } while (just_read != 0 && total_read < bytes);
-    if (total_read != bytes) {
-      // We seem to have a race condition here.
-      Fail("read"_ns, nullptr, OS_ERROR_RACE);
-      return NS_ERROR_FAILURE;
-    }
-
-    return NS_OK;
-  }
-
- protected:
-  /**
-   * Any steps that need to be taken before reading.
-   *
-   * In case of error, this method should call Fail() and return
-   * a failure code.
-   */
-  virtual nsresult BeforeRead() { return NS_OK; }
-
-  /**
-   * Proceed after reading.
-   */
-  virtual void AfterRead(TimeStamp aDispatchDate,
-                         ScopedArrayBufferContents& aBuffer) = 0;
-
- protected:
-  const nsString mPath;
-  const uint64_t mBytes;
-};
-
-/**
- * An implementation of a Read event that provides the data
- * as a TypedArray.
- */
-class DoReadToTypedArrayEvent final : public AbstractReadEvent {
- public:
-  DoReadToTypedArrayEvent(
-      const nsAString& aPath, const uint32_t aBytes,
-      nsMainThreadPtrHandle<nsINativeOSFileSuccessCallback>& aOnSuccess,
-      nsMainThreadPtrHandle<nsINativeOSFileErrorCallback>& aOnError)
-      : AbstractReadEvent(aPath, aBytes, aOnSuccess, aOnError),
-        mResult(new TypedArrayResult(TimeStamp::Now())) {}
-
-  ~DoReadToTypedArrayEvent() override {
-    // If AbstractReadEvent::Run() has bailed out, we may need to cleanup
-    // mResult, which is main-thread only data
-    if (!mResult) {
-      return;
-    }
-    NS_ReleaseOnMainThread("DoReadToTypedArrayEvent::mResult",
-                           mResult.forget());
-  }
-
- protected:
-  void AfterRead(TimeStamp aDispatchDate,
-                 ScopedArrayBufferContents& aBuffer) override {
-    MOZ_ASSERT(!NS_IsMainThread());
-    mResult->Init(aDispatchDate, TimeStamp::Now() - aDispatchDate,
-                  aBuffer.forget());
-    Succeed(mResult.forget());
-  }
-
- private:
-  RefPtr<TypedArrayResult> mResult;
-};
-
-/**
- * An implementation of a Read event that provides the data
- * as a JavaScript string.
- */
-class DoReadToStringEvent final : public AbstractReadEvent {
- public:
-  DoReadToStringEvent(
-      const nsAString& aPath, const nsACString& aEncoding,
-      const uint32_t aBytes,
-      nsMainThreadPtrHandle<nsINativeOSFileSuccessCallback>& aOnSuccess,
-      nsMainThreadPtrHandle<nsINativeOSFileErrorCallback>& aOnError)
-      : AbstractReadEvent(aPath, aBytes, aOnSuccess, aOnError),
-        mEncoding(aEncoding),
-        mResult(new StringResult(TimeStamp::Now())) {}
-
-  ~DoReadToStringEvent() override {
-    // If AbstraactReadEvent::Run() has bailed out, we may need to cleanup
-    // mResult, which is main-thread only data
-    if (!mResult) {
-      return;
-    }
-    NS_ReleaseOnMainThread("DoReadToStringEvent::mResult", mResult.forget());
-  }
-
- protected:
-  nsresult BeforeRead() override {
-    // Obtain the decoder. We do this before reading to avoid doing
-    // any unnecessary I/O in case the name of the encoding is incorrect.
-    MOZ_ASSERT(!NS_IsMainThread());
-    const Encoding* encoding = Encoding::ForLabel(mEncoding);
-    if (!encoding) {
-      Fail("Decode"_ns, mResult.forget(), OS_ERROR_INVAL);
-      return NS_ERROR_FAILURE;
-    }
-    mDecoder = encoding->NewDecoderWithBOMRemoval();
-    if (!mDecoder) {
-      Fail("DecoderForEncoding"_ns, mResult.forget(), OS_ERROR_INVAL);
-      return NS_ERROR_FAILURE;
-    }
-
-    return NS_OK;
-  }
-
-  void AfterRead(TimeStamp aDispatchDate,
-                 ScopedArrayBufferContents& aBuffer) override {
-    MOZ_ASSERT(!NS_IsMainThread());
-
-    auto src = Span(aBuffer.get().data, aBuffer.get().nbytes);
-
-    CheckedInt<size_t> needed = mDecoder->MaxUTF16BufferLength(src.Length());
-    if (!needed.isValid() ||
-        needed.value() > std::numeric_limits<nsAString::size_type>::max()) {
-      Fail("arithmetics"_ns, mResult.forget(), OS_ERROR_TOO_LARGE);
-      return;
-    }
-
-    nsString resultString;
-    auto resultSpan = resultString.GetMutableData(needed.value(), fallible);
-    if (!resultSpan) {
-      Fail("allocation"_ns, mResult.forget(), OS_ERROR_TOO_LARGE);
-      return;
-    }
-
-    // Yoric said on IRC that this method is normally called for the entire
-    // file, but that's not guaranteed. Retaining the bug that EOF in conversion
-    // isn't handled anywhere.
-    uint32_t result;
-    size_t read;
-    size_t written;
-    std::tie(result, read, written, std::ignore) =
-        mDecoder->DecodeToUTF16(src, *resultSpan, false);
-    MOZ_ASSERT(result == kInputEmpty);
-    MOZ_ASSERT(read == src.Length());
-    MOZ_ASSERT(written <= needed.value());
-    bool ok = resultString.SetLength(written, fallible);
-    if (!ok) {
-      Fail("allocation"_ns, mResult.forget(), OS_ERROR_TOO_LARGE);
-      return;
-    }
-
-    mResult->Init(aDispatchDate, TimeStamp::Now() - aDispatchDate,
-                  resultString);
-    Succeed(mResult.forget());
-  }
-
- private:
-  nsCString mEncoding;
-  mozilla::UniquePtr<mozilla::Decoder> mDecoder;
-  RefPtr<StringResult> mResult;
-};
-
-/**
- * An event implenting writing atomically to a file.
- */
-class DoWriteAtomicEvent : public AbstractDoEvent {
- public:
-  /**
-   * @param aPath The path of the file.
-   */
-  DoWriteAtomicEvent(
-      const nsAString& aPath, UniquePtr<char[], JS::FreePolicy> aBuffer,
-      const uint64_t aBytes, const nsAString& aTmpPath,
-      const nsAString& aBackupTo, const bool aFlush, const bool aNoOverwrite,
-      nsMainThreadPtrHandle<nsINativeOSFileSuccessCallback>& aOnSuccess,
-      nsMainThreadPtrHandle<nsINativeOSFileErrorCallback>& aOnError)
-      : AbstractDoEvent(aOnSuccess, aOnError),
-        mPath(aPath),
-        mBuffer(std::move(aBuffer)),
-        mBytes(aBytes),
-        mTmpPath(aTmpPath),
-        mBackupTo(aBackupTo),
-        mFlush(aFlush),
-        mNoOverwrite(aNoOverwrite),
-        mResult(new Int32Result(TimeStamp::Now())) {
-    MOZ_ASSERT(NS_IsMainThread());
-  }
-
-  ~DoWriteAtomicEvent() override {
-    // If Run() has bailed out, we may need to cleanup
-    // mResult, which is main-thread only data
-    if (!mResult) {
-      return;
-    }
-    NS_ReleaseOnMainThread("DoWriteAtomicEvent::mResult", mResult.forget());
-  }
-
-  NS_IMETHODIMP Run() override {
-    MOZ_ASSERT(!NS_IsMainThread());
-    TimeStamp dispatchDate = TimeStamp::Now();
-    int32_t bytesWritten;
-
-    nsresult rv = WriteAtomic(&bytesWritten);
-    if (NS_FAILED(rv)) {
-      return NS_OK;
-    }
-
-    AfterWriteAtomic(dispatchDate, bytesWritten);
-    return NS_OK;
-  }
-
- private:
-  /**
-   * Write atomically to a file.
-   * Must be called off the main thread.
-   * @param aBytesWritten will contain the total bytes written.
-   * This does not support compression in this implementation.
-   */
-  nsresult WriteAtomic(int32_t* aBytesWritten) {
-    MOZ_ASSERT(!NS_IsMainThread());
-
-    // Note: In Windows, many NSPR File I/O functions which act on pathnames
-    // do not handle UTF-16 encoding. Thus, we use the following functions
-    // to overcome this.
-    // PR_Access : GetFileAttributesW
-    // PR_Delete : DeleteFileW
-    // PR_OpenFile : CreateFileW followed by PR_ImportFile
-    // PR_Rename : MoveFileW
-
-    ScopedPRFileDesc file;
-    NS_ConvertUTF16toUTF8 path(mPath);
-    NS_ConvertUTF16toUTF8 tmpPath(mTmpPath);
-    NS_ConvertUTF16toUTF8 backupTo(mBackupTo);
-    bool fileExists = false;
-
-    if (!mTmpPath.IsVoid() || !mBackupTo.IsVoid() || mNoOverwrite) {
-      // fileExists needs to be computed in the case of tmpPath, since
-      // the rename behaves differently depending on whether the
-      // file already exists. It's also computed for backupTo since the
-      // backup can be skipped if the file does not exist in the first place.
-#if defined(XP_WIN)
-      fileExists = ::GetFileAttributesW(mPath.get()) != INVALID_FILE_ATTRIBUTES;
-#else
-      fileExists = PR_Access(path.get(), PR_ACCESS_EXISTS) == PR_SUCCESS;
-#endif  // defined(XP_WIN)
-    }
-
-    // Check noOverwrite.
-    if (mNoOverwrite && fileExists) {
-      Fail("noOverwrite"_ns, nullptr, OS_ERROR_FILE_EXISTS);
-      return NS_ERROR_FAILURE;
-    }
-
-    // Backup the original file if it exists.
-    if (!mBackupTo.IsVoid() && fileExists) {
-#if defined(XP_WIN)
-      if (::GetFileAttributesW(mBackupTo.get()) != INVALID_FILE_ATTRIBUTES) {
-        // The file specified by mBackupTo exists, so we need to delete it
-        // first.
-        if (::DeleteFileW(mBackupTo.get()) == false) {
-          Fail("delete"_ns, nullptr, ::GetLastError());
-          return NS_ERROR_FAILURE;
-        }
-      }
-
-      if (::MoveFileW(mPath.get(), mBackupTo.get()) == false) {
-        Fail("rename"_ns, nullptr, ::GetLastError());
-        return NS_ERROR_FAILURE;
-      }
-#else
-      if (PR_Access(backupTo.get(), PR_ACCESS_EXISTS) == PR_SUCCESS) {
-        // The file specified by mBackupTo exists, so we need to delete it
-        // first.
-        if (PR_Delete(backupTo.get()) == PR_FAILURE) {
-          Fail("delete"_ns, nullptr, PR_GetOSError());
-          return NS_ERROR_FAILURE;
-        }
-      }
-
-      if (PR_Rename(path.get(), backupTo.get()) == PR_FAILURE) {
-        Fail("rename"_ns, nullptr, PR_GetOSError());
-        return NS_ERROR_FAILURE;
-      }
-#endif  // defined(XP_WIN)
-    }
-
-#if defined(XP_WIN)
-    // In addition to not handling UTF-16 encoding in file paths,
-    // PR_OpenFile opens files without sharing, which is not the
-    // general semantics of OS.File.
-    HANDLE handle;
-    // if we're dealing with a tmpFile, we need to write there.
-    if (!mTmpPath.IsVoid()) {
-      handle = ::CreateFileW(
-          mTmpPath.get(), GENERIC_WRITE,
-          FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
-          /*Security attributes*/ nullptr,
-          // CREATE_ALWAYS is used since since we need to create the temporary
-          // file, which we don't care about overwriting.
-          CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_WRITE_THROUGH,
-          /*Template file*/ nullptr);
-    } else {
-      handle = ::CreateFileW(
-          mPath.get(), GENERIC_WRITE,
-          FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
-          /*Security attributes*/ nullptr,
-          // CREATE_ALWAYS is used since since have already checked the
-          // noOverwrite condition, and thus can overwrite safely.
-          CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_WRITE_THROUGH,
-          /*Template file*/ nullptr);
-    }
-
-    if (handle == INVALID_HANDLE_VALUE) {
-      Fail("open"_ns, nullptr, ::GetLastError());
-      return NS_ERROR_FAILURE;
-    }
-
-    file = PR_ImportFile((PROsfd)handle);
-    if (!file) {
-      // |file| is closed by PR_ImportFile
-      Fail("ImportFile"_ns, nullptr, PR_GetOSError());
-      return NS_ERROR_FAILURE;
-    }
-
-#else
-    // if we're dealing with a tmpFile, we need to write there.
-    if (!mTmpPath.IsVoid()) {
-      file =
-          PR_OpenFile(tmpPath.get(), PR_WRONLY | PR_CREATE_FILE | PR_TRUNCATE,
-                      PR_IRUSR | PR_IWUSR);
-    } else {
-      file = PR_OpenFile(path.get(), PR_WRONLY | PR_CREATE_FILE | PR_TRUNCATE,
-                         PR_IRUSR | PR_IWUSR);
-    }
-
-    if (!file) {
-      Fail("open"_ns, nullptr, PR_GetOSError());
-      return NS_ERROR_FAILURE;
-    }
-#endif  // defined(XP_WIN)
-
-    int32_t bytesWrittenSuccess =
-        PR_Write(file, (void*)(mBuffer.get()), mBytes);
-
-    if (bytesWrittenSuccess == -1) {
-      Fail("write"_ns, nullptr, PR_GetOSError());
-      return NS_ERROR_FAILURE;
-    }
-
-    // Apply any tmpPath renames.
-    if (!mTmpPath.IsVoid()) {
-      if (mBackupTo.IsVoid() && fileExists) {
-        // We need to delete the old file first, if it exists and we haven't
-        // already renamed it as a part of backing it up.
-#if defined(XP_WIN)
-        if (::DeleteFileW(mPath.get()) == false) {
-          Fail("delete"_ns, nullptr, ::GetLastError());
-          return NS_ERROR_FAILURE;
-        }
-#else
-        if (PR_Delete(path.get()) == PR_FAILURE) {
-          Fail("delete"_ns, nullptr, PR_GetOSError());
-          return NS_ERROR_FAILURE;
-        }
-#endif  // defined(XP_WIN)
-      }
-
-#if defined(XP_WIN)
-      if (::MoveFileW(mTmpPath.get(), mPath.get()) == false) {
-        Fail("rename"_ns, nullptr, ::GetLastError());
-        return NS_ERROR_FAILURE;
-      }
-#else
-      if (PR_Rename(tmpPath.get(), path.get()) == PR_FAILURE) {
-        Fail("rename"_ns, nullptr, PR_GetOSError());
-        return NS_ERROR_FAILURE;
-      }
-#endif  // defined(XP_WIN)
-    }
-
-    if (mFlush) {
-      if (PR_Sync(file) == PR_FAILURE) {
-        Fail("sync"_ns, nullptr, PR_GetOSError());
-        return NS_ERROR_FAILURE;
-      }
-    }
-
-    *aBytesWritten = bytesWrittenSuccess;
-    return NS_OK;
-  }
-
- protected:
-  nsresult AfterWriteAtomic(TimeStamp aDispatchDate, int32_t aBytesWritten) {
-    MOZ_ASSERT(!NS_IsMainThread());
-    mResult->Init(aDispatchDate, TimeStamp::Now() - aDispatchDate,
-                  aBytesWritten);
-    Succeed(mResult.forget());
-    return NS_OK;
-  }
-
-  const nsString mPath;
-  const UniquePtr<char[], JS::FreePolicy> mBuffer;
-  const int32_t mBytes;
-  const nsString mTmpPath;
-  const nsString mBackupTo;
-  const bool mFlush;
-  const bool mNoOverwrite;
-
- private:
-  RefPtr<Int32Result> mResult;
-};
-
-}  // namespace
-
-// The OS.File service
-
-NS_IMPL_ISUPPORTS(NativeOSFileInternalsService,
-                  nsINativeOSFileInternalsService);
-
-NS_IMETHODIMP
-NativeOSFileInternalsService::Read(const nsAString& aPath,
-                                   JS::Handle<JS::Value> aOptions,
-                                   nsINativeOSFileSuccessCallback* aOnSuccess,
-                                   nsINativeOSFileErrorCallback* aOnError,
-                                   JSContext* cx) {
-  // Extract options
-  nsCString encoding;
-  uint64_t bytes = UINT64_MAX;
-
-  if (aOptions.isObject()) {
-    dom::NativeOSFileReadOptions dict;
-    if (!dict.Init(cx, aOptions)) {
-      return NS_ERROR_INVALID_ARG;
-    }
-
-    if (dict.mEncoding.WasPassed()) {
-      CopyUTF16toUTF8(dict.mEncoding.Value(), encoding);
-    }
-
-    if (dict.mBytes.WasPassed() && !dict.mBytes.Value().IsNull()) {
-      bytes = dict.mBytes.Value().Value();
-    }
-  }
-
-  // Prepare the off main thread event and dispatch it
-  nsCOMPtr<nsINativeOSFileSuccessCallback> onSuccess(aOnSuccess);
-  nsMainThreadPtrHandle<nsINativeOSFileSuccessCallback> onSuccessHandle(
-      new nsMainThreadPtrHolder<nsINativeOSFileSuccessCallback>(
-          "nsINativeOSFileSuccessCallback", onSuccess));
-  nsCOMPtr<nsINativeOSFileErrorCallback> onError(aOnError);
-  nsMainThreadPtrHandle<nsINativeOSFileErrorCallback> onErrorHandle(
-      new nsMainThreadPtrHolder<nsINativeOSFileErrorCallback>(
-          "nsINativeOSFileErrorCallback", onError));
-
-  RefPtr<AbstractDoEvent> event;
-  if (encoding.IsEmpty()) {
-    event = new DoReadToTypedArrayEvent(aPath, bytes, onSuccessHandle,
-                                        onErrorHandle);
-  } else {
-    event = new DoReadToStringEvent(aPath, encoding, bytes, onSuccessHandle,
-                                    onErrorHandle);
-  }
-
-  nsresult rv;
-  nsCOMPtr<nsIEventTarget> target =
-      do_GetService(NS_STREAMTRANSPORTSERVICE_CONTRACTID, &rv);
-
-  if (NS_FAILED(rv)) {
-    return rv;
-  }
-  return target->Dispatch(event, NS_DISPATCH_NORMAL);
-}
-
-// Note: This method steals the contents of `aBuffer`.
-NS_IMETHODIMP
-NativeOSFileInternalsService::WriteAtomic(
-    const nsAString& aPath, JS::Handle<JS::Value> aBuffer,
-    JS::Handle<JS::Value> aOptions, nsINativeOSFileSuccessCallback* aOnSuccess,
-    nsINativeOSFileErrorCallback* aOnError, JSContext* cx) {
-  MOZ_ASSERT(NS_IsMainThread());
-  // Extract typed-array/string into buffer. We also need to store the length
-  // of the buffer as that may be required if not provided in `aOptions`.
-  UniquePtr<char[], JS::FreePolicy> buffer;
-  int32_t bytes;
-
-  // The incoming buffer must be an Object.
-  if (!aBuffer.isObject()) {
-    return NS_ERROR_INVALID_ARG;
-  }
-
-  JS::Rooted<JSObject*> bufferObject(cx, nullptr);
-  if (!JS_ValueToObject(cx, aBuffer, &bufferObject)) {
-    return NS_ERROR_FAILURE;
-  }
-  if (!JS::IsArrayBufferObject(bufferObject.get())) {
-    return NS_ERROR_INVALID_ARG;
-  }
-
-  {
-    // Throw for large ArrayBuffers to prevent truncation.
-    size_t len = JS::GetArrayBufferByteLength(bufferObject.get());
-    if (len > INT32_MAX) {
-      return NS_ERROR_INVALID_ARG;
-    }
-    bytes = len;
-  }
-  buffer.reset(
-      static_cast<char*>(JS::StealArrayBufferContents(cx, bufferObject)));
-
-  if (!buffer) {
-    return NS_ERROR_FAILURE;
-  }
-
-  // Extract options.
-  dom::NativeOSFileWriteAtomicOptions dict;
-
-  if (aOptions.isObject()) {
-    if (!dict.Init(cx, aOptions)) {
-      return NS_ERROR_INVALID_ARG;
-    }
-  } else {
-    // If an options object is not provided, initializing with a `null`
-    // value, which will give a set of defaults defined in the WebIDL binding.
-    if (!dict.Init(cx, JS::NullHandleValue)) {
-      return NS_ERROR_FAILURE;
-    }
-  }
-
-  if (dict.mBytes.WasPassed() && !dict.mBytes.Value().IsNull()) {
-    // We need to check size and cast because NSPR and WebIDL have different
-    // types.
-    if (dict.mBytes.Value().Value() > PR_INT32_MAX) {
-      return NS_ERROR_INVALID_ARG;
-    }
-    bytes = (int32_t)(dict.mBytes.Value().Value());
-  }
-
-  // Prepare the off main thread event and dispatch it
-  nsCOMPtr<nsINativeOSFileSuccessCallback> onSuccess(aOnSuccess);
-  nsMainThreadPtrHandle<nsINativeOSFileSuccessCallback> onSuccessHandle(
-      new nsMainThreadPtrHolder<nsINativeOSFileSuccessCallback>(
-          "nsINativeOSFileSuccessCallback", onSuccess));
-  nsCOMPtr<nsINativeOSFileErrorCallback> onError(aOnError);
-  nsMainThreadPtrHandle<nsINativeOSFileErrorCallback> onErrorHandle(
-      new nsMainThreadPtrHolder<nsINativeOSFileErrorCallback>(
-          "nsINativeOSFileErrorCallback", onError));
-
-  RefPtr<AbstractDoEvent> event = new DoWriteAtomicEvent(
-      aPath, std::move(buffer), bytes, dict.mTmpPath, dict.mBackupTo,
-      dict.mFlush, dict.mNoOverwrite, onSuccessHandle, onErrorHandle);
-  nsresult rv;
-  nsCOMPtr<nsIEventTarget> target =
-      do_GetService(NS_STREAMTRANSPORTSERVICE_CONTRACTID, &rv);
-
-  if (NS_FAILED(rv)) {
-    return rv;
-  }
-
-  return target->Dispatch(event, NS_DISPATCH_NORMAL);
-}
-
-}  // namespace mozilla

deleted file mode 100644
--- a/toolkit/components/osfile/NativeOSFileInternals.h
+++ /dev/null
@@ -1,29 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set ts=8 sts=2 et sw=2 tw=80: */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#ifndef mozilla_nativeosfileinternalservice_h__
-#define mozilla_nativeosfileinternalservice_h__
-
-#include "nsINativeOSFileInternals.h"
-
-#include "nsISupports.h"
-
-namespace mozilla {
-
-class NativeOSFileInternalsService final
-    : public nsINativeOSFileInternalsService {
- public:
-  NS_DECL_ISUPPORTS
-  NS_DECL_NSINATIVEOSFILEINTERNALSSERVICE
- private:
-  ~NativeOSFileInternalsService() = default;
-  // Avoid accidental use of built-in operator=
-  void operator=(const NativeOSFileInternalsService& other) = delete;
-};
-
-}  // namespace mozilla
-
-#endif  // mozilla_finalizationwitnessservice_h__

deleted file mode 100644
--- a/toolkit/components/osfile/modules/moz.build
+++ /dev/null
@@ -1,29 +0,0 @@
-# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
-# vim: set filetype=python:
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at http://mozilla.org/MPL/2.0/.
-
-EXTRA_JS_MODULES.osfile += [
-    "osfile_async_front.jsm",
-    "osfile_async_worker.js",
-    "osfile_native.jsm",
-    "osfile_shared_allthreads.jsm",
-    "osfile_shared_front.js",
-    "ospath.jsm",
-    "ospath_unix.jsm",
-    "ospath_win.jsm",
-]
-
-if CONFIG["OS_TARGET"] == "WINNT":
-    EXTRA_JS_MODULES.osfile += [
-        "osfile_win_allthreads.jsm",
-        "osfile_win_back.js",
-        "osfile_win_front.js",
-    ]
-else:
-    EXTRA_JS_MODULES.osfile += [
-        "osfile_unix_allthreads.jsm",
-        "osfile_unix_back.js",
-        "osfile_unix_front.js",
-    ]

deleted file mode 100644
--- a/toolkit/components/osfile/modules/osfile_async_front.jsm
+++ /dev/null
@@ -1,1570 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-/**
- * Asynchronous front-end for OS.File.
- *
- * This front-end is meant to be imported from the main thread. In turn,
- * it spawns one worker (perhaps more in the future) and delegates all
- * disk I/O to this worker.
- *
- * Documentation note: most of the functions and methods in this module
- * return promises. For clarity, we denote as follows a promise that may resolve
- * with type |A| and some value |value| or reject with type |B| and some
- * reason |reason|
- * @resolves {A} value
- * @rejects {B} reason
- */
-
-"use strict";
-
-// Scheduler is exported for test-only usage.
-var EXPORTED_SYMBOLS = ["OS", "Scheduler"];
-
-var SharedAll = ChromeUtils.import(
-  "resource://gre/modules/osfile/osfile_shared_allthreads.jsm"
-);
-const { clearInterval, setInterval } = ChromeUtils.importESModule(
-  "resource://gre/modules/Timer.sys.mjs"
-);
-
-// Boilerplate, to simplify the transition to require()
-var LOG = SharedAll.LOG.bind(SharedAll, "Controller");
-var isTypedArray = SharedAll.isTypedArray;
-
-// The constructor for file errors.
-var SysAll;
-if (SharedAll.Constants.Win) {
-  SysAll = ChromeUtils.import(
-    "resource://gre/modules/osfile/osfile_win_allthreads.jsm"
-  );
-} else if (SharedAll.Constants.libc) {
-  SysAll = ChromeUtils.import(
-    "resource://gre/modules/osfile/osfile_unix_allthreads.jsm"
-  );
-} else {
-  throw new Error("I am neither under Windows nor under a Posix system");
-}
-var OSError = SysAll.Error;
-var Type = SysAll.Type;
-
-var Path = ChromeUtils.import("resource://gre/modules/osfile/ospath.jsm");
-
-const lazy = {};
-
-// The library of promises.
-ChromeUtils.defineESModuleGetters(lazy, {
-  PromiseUtils: "resource://gre/modules/PromiseUtils.sys.mjs",
-});
-
-// The implementation of communications
-const { BasePromiseWorker } = ChromeUtils.import(
-  "resource://gre/modules/PromiseWorker.jsm"
-);
-const { AsyncShutdown } = ChromeUtils.importESModule(
-  "resource://gre/modules/AsyncShutdown.sys.mjs"
-);
-var Native = ChromeUtils.import(
-  "resource://gre/modules/osfile/osfile_native.jsm"
-);
-
-// It's possible for osfile.jsm to get imported before the profile is
-// set up. In this case, some path constants aren't yet available.
-// Here, we make them lazy loaders.
-
-function lazyPathGetter(constProp, dirKey) {
-  return function() {
-    let path;
-    try {
-      path = Services.dirsvc.get(dirKey, Ci.nsIFile).path;
-      delete SharedAll.Constants.Path[constProp];
-      SharedAll.Constants.Path[constProp] = path;
-    } catch (ex) {
-      // Ignore errors if the value still isn't available. Hopefully
-      // the next access will return it.
-    }
-
-    return path;
-  };
-}
-
-for (let [constProp, dirKey] of [
-  ["localProfileDir", "ProfLD"],
-  ["profileDir", "ProfD"],
-  ["userApplicationDataDir", "UAppData"],
-  ["winAppDataDir", "AppData"],
-  ["winLocalAppDataDir", "LocalAppData"],
-  ["winStartMenuProgsDir", "Progs"],
-  ["tmpDir", "TmpD"],
-  ["homeDir", "Home"],
-  ["macUserLibDir", "ULibDir"],
-]) {
-  if (constProp in SharedAll.Constants.Path) {
-    continue;
-  }
-
-  LOG(
-    "Installing lazy getter for OS.Constants.Path." +
-      constProp +
-      " because it isn't defined and profile may not be loaded."
-  );
-  Object.defineProperty(SharedAll.Constants.Path, constProp, {
-    get: lazyPathGetter(constProp, dirKey),
-  });
-}
-
-/**
- * Return a shallow clone of the enumerable properties of an object.
- */
-var clone = SharedAll.clone;
-
-/**
- * Extract a shortened version of an object, fit for logging.
- *
- * This function returns a copy of the original object in which all
- * long strings, Arrays, TypedArrays, ArrayBuffers are removed and
- * replaced with placeholders. Use this function to sanitize objects
- * if you wish to log them or to keep them in memory.
- *
- * @param {*} obj The obj to shorten.
- * @return {*} array A shorter object, fit for logging.
- */
-function summarizeObject(obj) {
-  if (!obj) {
-    return null;
-  }
-  if (typeof obj == "string") {
-    if (obj.length > 1024) {
-      return { "Long string": obj.length };
-    }
-    return obj;
-  }
-  if (typeof obj == "object") {
-    if (Array.isArray(obj)) {
-      if (obj.length > 32) {
-        return { "Long array": obj.length };
-      }
-      return obj.map(summarizeObject);
-    }
-    if ("byteLength" in obj) {
-      // Assume TypedArray or ArrayBuffer
-      return { "Binary Data": obj.byteLength };
-    }
-    let result = {};
-    for (let k of Object.keys(obj)) {
-      result[k] = summarizeObject(obj[k]);
-    }
-    return result;
-  }
-  return obj;
-}
-
-var Scheduler = {
-  /**
-   * |true| once we have sent at least one message to the worker.
-   * This field is unaffected by resetting the worker.
-   */
-  launched: false,
-
-  /**
-   * |true| once shutdown has begun i.e. we should reject any
-   * message, including resets.
-   */
-  shutdown: false,
-
-  /**
-   * A promise resolved once all currently pending operations are complete.
-   *
-   * This promise is never rejected and the result is always undefined.
-   */
-  queue: Promise.resolve(),
-
-  /**
-   * A promise resolved once all currently pending `kill` operations
-   * are complete.
-   *
-   * This promise is never rejected and the result is always undefined.
-   */
-  _killQueue: Promise.resolve(),
-
-  /**
-   * Miscellaneous debugging information
-   */
-  Debugging: {
-    /**
-     * The latest message sent and still waiting for a reply.
-     */
-    latestSent: undefined,
-
-    /**
-     * The latest reply received, or null if we are waiting for a reply.
-     */
-    latestReceived: undefined,
-
-    /**
-     * Number of messages sent to the worker. This includes the
-     * initial SET_DEBUG, if applicable.
-     */
-    messagesSent: 0,
-
-    /**
-     * Total number of messages ever queued, including the messages
-     * sent.
-     */
-    messagesQueued: 0,
-
-    /**
-     * Number of messages received from the worker.
-     */
-    messagesReceived: 0,
-  },
-
-  /**
-   * A timer used to automatically shut down the worker after some time.
-   */
-  resetTimer: null,
-
-  /**
-   * A flag indicating whether we had some activities when waiting the
-   * timer and if it's not we can shut down the worker.
-   */
-  hasRecentActivity: false,
-
-  /**
-   * The worker to which to send requests.
-   *
-   * If the worker has never been created or has been reset, this is a
-   * fresh worker, initialized with osfile_async_worker.js.
-   *
-   * @type {PromiseWorker}
-   */
-  get worker() {
-    if (!this._worker) {
-      // Either the worker has never been created or it has been
-      // reset.  In either case, it is time to instantiate the worker.
-      this._worker = new BasePromiseWorker(
-        "resource://gre/modules/osfile/osfile_async_worker.js"
-      );
-      this._worker.log = LOG;
-      this._worker.ExceptionHandlers["OS.File.Error"] = OSError.fromMsg;
-
-      let delay = Services.prefs.getIntPref("osfile.reset_worker_delay", 0);
-      if (delay) {
-        this.resetTimer = setInterval(() => {
-          if (this.hasRecentActivity) {
-            this.hasRecentActivity = false;
-            return;
-          }
-          clearInterval(this.resetTimer);
-          Scheduler.kill({ reset: true, shutdown: false });
-        }, delay);
-      }
-    }
-    return this._worker;
-  },
-
-  _worker: null,
-
-  /**
-   * Restart the OS.File worker killer timer.
-   */
-  restartTimer(arg) {
-    this.hasRecentActivity = true;
-  },
-
-  /**
-   * Shutdown OS.File.
-   *
-   * @param {*} options
-   * - {boolean} shutdown If |true|, reject any further request. Otherwise,
-   *   further requests will resurrect the worker.
-   * - {boolean} reset If |true|, instruct the worker to shutdown if this
-   *   would not cause leaks. Otherwise, assume that the worker will be shutdown
-   *   through some other mean.
-   */
-  kill({ shutdown, reset }) {
-    // Grab the kill queue to make sure that we
-    // cannot be interrupted by another call to `kill`.
-    let killQueue = this._killQueue;
-
-    // Deactivate the queue, to ensure that no message is sent
-    // to an obsolete worker (we reactivate it in the `finally`).
-    // This needs to be done right now so that we maintain relative
-    // ordering with calls to post(), etc.
-    let deferred = lazy.PromiseUtils.defer();
-    let savedQueue = this.queue;
-    this.queue = deferred.promise;
-
-    return (this._killQueue = (async () => {
-      await killQueue;
-      // From this point, and until the end of the Task, we are the
-      // only call to `kill`, regardless of any `yield`.
-
-      await savedQueue;
-
-      try {
-        // Enter critical section: no yield in this block
-        // (we want to make sure that we remain the only
-        // request in the queue).
-
-        if (!this.launched || this.shutdown || !this._worker) {
-          // Nothing to kill
-          this.shutdown = this.shutdown || shutdown;
-          this._worker = null;
-          return null;
-        }
-
-        // Exit critical section
-
-        let message = ["Meta_shutdown", [reset]];
-
-        Scheduler.latestReceived = [];
-        let stack = new Error().stack;
-        Scheduler.latestSent = [Date.now(), stack, ...message];
-
-        // Wait for result
-        let resources;
-        try {
-          resources = await this._worker.post(...message);
-
-          Scheduler.latestReceived = [Date.now(), message];
-        } catch (ex) {
-          LOG("Could not dispatch Meta_reset", ex);
-          // It's most likely a programmer error, but we'll assume that
-          // the worker has been shutdown, as it's less risky than the
-          // opposite stance.
-          resources = {
-            openedFiles: [],
-            openedDirectoryIterators: [],
-            killed: true,
-          };
-
-          Scheduler.latestReceived = [Date.now(), message, ex];
-        }
-
-        let { openedFiles, openedDirectoryIterators, killed } = resources;
-        if (
-          !reset &&
-          ((openedFiles && openedFiles.length) ||
-            (openedDirectoryIterators && openedDirectoryIterators.length))
-        ) {
-          // The worker still holds resources. Report them.
-
-          let msg = "";
-          if (openedFiles.length) {
-            msg +=
-              "The following files are still open:\n" + openedFiles.join("\n");
-          }
-          if (openedDirectoryIterators.length) {
-            msg +=
-              "The following directory iterators are still open:\n" +
-              openedDirectoryIterators.join("\n");
-          }
-
-          LOG("WARNING: File descriptors leaks detected.\n" + msg);
-        }
-
-        // Make sure that we do not leave an invalid |worker| around.
-        if (killed || shutdown) {
-          this._worker = null;
-        }
-
-        this.shutdown = shutdown;
-
-        return resources;
-      } finally {
-        // Resume accepting messages. If we have set |shutdown| to |true|,
-        // any pending/future request will be rejected. Otherwise, any
-        // pending/future request will spawn a new worker if necessary.
-        deferred.resolve();
-      }
-    })());
-  },
-
-  /**
-   * Push a task at the end of the queue.
-   *
-   * @param {function} code A function returning a Promise.
-   * This function will be executed once all the previously
-   * pushed tasks have completed.
-   * @return {Promise} A promise with the same behavior as
-   * the promise returned by |code|.
-   */
-  push(code) {
-    let promise = this.queue.then(code);
-    // By definition, |this.queue| can never reject.
-    this.queue = promise.catch(() => undefined);
-    // Fork |promise| to ensure that uncaught errors are reported
-    return promise.then();
-  },
-
-  /**
-   * Post a message to the worker thread.
-   *
-   * @param {string} method The name of the method to call.
-   * @param {...} args The arguments to pass to the method. These arguments
-   * must be clonable.
-   * The last argument by convention may be an object `options`, with some of
-   * the following fields:
-   *   - {number|null} outSerializationDuration A parameter to be filled with
-   *     duration of the `this.worker.post` method.
-   * @return {Promise} A promise conveying the result/error caused by
-   * calling |method| with arguments |args|.
-   */
-  post: function post(method, args = undefined, closure = undefined) {
-    if (this.shutdown) {
-      LOG(
-        "OS.File is not available anymore. The following request has been rejected.",
-        method,
-        args
-      );
-      return Promise.reject(
-        new Error("OS.File has been shut down. Rejecting post to " + method)
-      );
-    }
-    let firstLaunch = !this.launched;
-    this.launched = true;
-
-    if (firstLaunch && SharedAll.Config.DEBUG) {
-      // If we have delayed sending SET_DEBUG, do it now.
-      this.worker.post("SET_DEBUG", [true]);
-      Scheduler.Debugging.messagesSent++;
-    }
-
-    Scheduler.Debugging.messagesQueued++;
-    return this.push(async () => {
-      if (this.shutdown) {
-        LOG(
-          "OS.File is not available anymore. The following request has been rejected.",
-          method,
-          args
-        );
-        throw new Error(
-          "OS.File has been shut down. Rejecting request to " + method
-        );
-      }
-
-      // Update debugging information. As |args| may be quite
-      // expensive, we only keep a shortened version of it.
-      Scheduler.Debugging.latestReceived = null;
-      Scheduler.Debugging.latestSent = [
-        Date.now(),
-        method,
-        summarizeObject(args),
-      ];
-
-      // Don't kill the worker just yet
-      Scheduler.restartTimer();
-
-      // The last object inside the args may be an options object.
-      let options = null;
-      if (
-        args &&
-        args.length >= 1 &&
-        typeof args[args.length - 1] === "object"
-      ) {
-        options = args[args.length - 1];
-      }
-
-      let reply;
-      try {
-        try {
-          Scheduler.Debugging.messagesSent++;
-          Scheduler.Debugging.latestSent = Scheduler.Debugging.latestSent.slice(
-            0,
-            2
-          );
-          let serializationStartTimeMs = Date.now();
-          reply = await this.worker.post(method, args, closure);
-          let serializationEndTimeMs = Date.now();
-          Scheduler.Debugging.latestReceived = [
-            Date.now(),
-            summarizeObject(reply),
-          ];
-
-          // There were no options for recording the serialization duration.
-          if (options && "outSerializationDuration" in options) {
-            // The difference might be negative for very fast operations, since Date.now() may not be monotonic.
-            let serializationDurationMs = Math.max(
-              0,
-              serializationEndTimeMs - serializationStartTimeMs
-            );
-
-            if (typeof options.outSerializationDuration === "number") {
-              options.outSerializationDuration += serializationDurationMs;
-            } else {
-              options.outSerializationDuration = serializationDurationMs;
-            }
-          }
-          return reply;
-        } finally {
-          Scheduler.Debugging.messagesReceived++;
-        }
-      } catch (error) {
-        Scheduler.Debugging.latestReceived = [
-          Date.now(),
-          error.message,
-          error.fileName,
-          error.lineNumber,
-        ];
-        throw error;
-      } finally {
-        if (firstLaunch) {
-          Scheduler._updateTelemetry();
-        }
-        Scheduler.restartTimer();
-      }
-    });
-  },
-
-  /**
-   * Post Telemetry statistics.
-   *
-   * This is only useful on first launch.
-   */
-  _updateTelemetry() {
-    let worker = this.worker;
-    let workerTimeStamps = worker.workerTimeStamps;
-    if (!workerTimeStamps) {
-      // If the first call to OS.File results in an uncaught errors,
-      // the timestamps are absent. As this case is a developer error,
-      // let's not waste time attempting to extract telemetry from it.
-      return;
-    }
-    let HISTOGRAM_LAUNCH = Services.telemetry.getHistogramById(
-      "OSFILE_WORKER_LAUNCH_MS"
-    );
-    HISTOGRAM_LAUNCH.add(
-      worker.workerTimeStamps.entered - worker.launchTimeStamp
-    );
-
-    let HISTOGRAM_READY = Services.telemetry.getHistogramById(
-      "OSFILE_WORKER_READY_MS"
-    );
-    HISTOGRAM_READY.add(
-      worker.workerTimeStamps.loaded - worker.launchTimeStamp
-    );
-  },
-};
-
-const PREF_OSFILE_LOG = "toolkit.osfile.log";
-const PREF_OSFILE_LOG_REDIRECT = "toolkit.osfile.log.redirect";
-
-/**
- * Safely read a PREF_OSFILE_LOG preference.
- * Returns a value read or, in case of an error, oldPref or false.
- *
- * @param bool oldPref
- *        An optional value that the DEBUG flag was set to previously.
- */
-function readDebugPref(prefName, oldPref = false) {
-  // If neither pref nor oldPref were set, default it to false.
-  return Services.prefs.getBoolPref(prefName, oldPref);
-}
-
-/**
- * Listen to PREF_OSFILE_LOG changes and update gShouldLog flag
- * appropriately.
- */
-Services.prefs.addObserver(PREF_OSFILE_LOG, function prefObserver(
-  aSubject,
-  aTopic,
-  aData
-) {
-  SharedAll.Config.DEBUG = readDebugPref(
-    PREF_OSFILE_LOG,
-    SharedAll.Config.DEBUG
-  );
-  if (Scheduler.launched) {
-    // Don't start the worker just to set this preference.
-    Scheduler.post("SET_DEBUG", [SharedAll.Config.DEBUG]);
-  }
-});
-SharedAll.Config.DEBUG = readDebugPref(PREF_OSFILE_LOG, false);
-
-Services.prefs.addObserver(PREF_OSFILE_LOG_REDIRECT, function prefObserver(
-  aSubject,
-  aTopic,
-  aData
-) {
-  SharedAll.Config.TEST = readDebugPref(
-    PREF_OSFILE_LOG_REDIRECT,
-    OS.Shared.TEST
-  );
-});
-SharedAll.Config.TEST = readDebugPref(PREF_OSFILE_LOG_REDIRECT, false);
-
-/**
- * If |true|, use the native implementaiton of OS.File methods
- * whenever possible. Otherwise, force the use of the JS version.
- */
-var nativeWheneverAvailable = true;
-const PREF_OSFILE_NATIVE = "toolkit.osfile.native";
-Services.prefs.addObserver(PREF_OSFILE_NATIVE, function prefObserver(
-  aSubject,
-  aTopic,
-  aData
-) {
-  nativeWheneverAvailable = readDebugPref(
-    PREF_OSFILE_NATIVE,
-    nativeWheneverAvailable
-  );
-});
-
-// Update worker's DEBUG flag if it's true.
-// Don't start the worker just for this, though.
-if (SharedAll.Config.DEBUG && Scheduler.launched) {
-  Scheduler.post("SET_DEBUG", [true]);
-}
-
-// Preference used to configure test shutdown observer.
-const PREF_OSFILE_TEST_SHUTDOWN_OBSERVER =
-  "toolkit.osfile.test.shutdown.observer";
-
-AsyncShutdown.xpcomWillShutdown.addBlocker(
-  "OS.File: flush pending requests, warn about unclosed files, shut down service.",
-  async function() {
-    // Give clients a last chance to enqueue requests.
-    await Barriers.shutdown.wait({ crashAfterMS: null });
-
-    // Wait until all requests are complete and kill the worker.
-    await Scheduler.kill({ reset: false, shutdown: true });
-  },
-  () => {
-    let details = Barriers.getDetails();
-    details.clients = Barriers.shutdown.state;
-    return details;
-  }
-);
-
-// Attaching an observer for PREF_OSFILE_TEST_SHUTDOWN_OBSERVER to enable or
-// disable the test shutdown event observer.
-// Note: By default the PREF_OSFILE_TEST_SHUTDOWN_OBSERVER is unset.
-// Note: This is meant to be used for testing purposes only.
-Services.prefs.addObserver(
-  PREF_OSFILE_TEST_SHUTDOWN_OBSERVER,
-  function prefObserver() {
-    // The temporary phase topic used to trigger the unclosed
-    // phase warning.
-    let TOPIC = Services.prefs.getCharPref(
-      PREF_OSFILE_TEST_SHUTDOWN_OBSERVER,
-      ""
-    );
-    if (TOPIC) {
-      // Generate a phase, add a blocker.
-      // Note that this can work only if AsyncShutdown itself has been
-      // configured for testing by the testsuite.
-      let phase = AsyncShutdown._getPhase(TOPIC);
-      phase.addBlocker(
-        "(for testing purposes) OS.File: warn about unclosed files",
-        () => Scheduler.kill({ shutdown: false, reset: false })
-      );
-    }
-  }
-);
-
-/**
- * Representation of a file, with asynchronous methods.
- *
- * @param {*} fdmsg The _message_ representing the platform-specific file
- * handle.
- *
- * @constructor
- */
-var File = function File(fdmsg) {
-  // FIXME: At the moment, |File| does not close on finalize
-  // (see bug 777715)
-  this._fdmsg = fdmsg;
-  this._closeResult = null;
-  this._closed = null;
-};
-
-File.prototype = {
-  /**
-   * Close a file asynchronously.
-   *
-   * This method is idempotent.
-   *
-   * @return {promise}
-   * @resolves {null}
-   * @rejects {OS.File.Error}
-   */
-  close: function close() {
-    if (this._fdmsg != null) {
-      let msg = this._fdmsg;
-      this._fdmsg = null;
-      return (this._closeResult = Scheduler.post(
-        "File_prototype_close",
-        [msg],
-        this
-      ));
-    }
-    return this._closeResult;
-  },
-
-  /**
-   * Fetch information about the file.
-   *
-   * @return {promise}
-   * @resolves {OS.File.Info} The latest information about the file.
-   * @rejects {OS.File.Error}
-   */
-  stat: function stat() {
-    return Scheduler.post("File_prototype_stat", [this._fdmsg], this).then(
-      File.Info.fromMsg
-    );
-  },
-
-  /**
-   * Write bytes from a buffer to this file.
-   *
-   * Note that, by default, this function may perform several I/O
-   * operations to ensure that the buffer is fully written.
-   *
-   * @param {Typed array | C pointer} buffer The buffer in which the
-   * the bytes are stored. The buffer must be large enough to
-   * accomodate |bytes| bytes. Using the buffer before the operation
-   * is complete is a BAD IDEA.
-   * @param {*=} options Optionally, an object that may contain the
-   * following fields:
-   * - {number} bytes The number of |bytes| to write from the buffer. If
-   * unspecified, this is |buffer.byteLength|. Note that |bytes| is required
-   * if |buffer| is a C pointer.
-   *
-   * @return {number} The number of bytes actually written.
-   */
-  write: function write(buffer, options = {}) {
-    // If |buffer| is a typed array and there is no |bytes| options,
-    // we need to extract the |byteLength| now, as it will be lost
-    // by communication.
-    // Options might be a nullish value, so better check for that before using
-    // the |in| operator.
-    if (isTypedArray(buffer) && !(options && "bytes" in options)) {
-      // Preserve reference to option |outExecutionDuration|, |outSerializationDuration|, if it is passed.
-      options = clone(options, [
-        "outExecutionDuration",
-        "outSerializationDuration",
-      ]);
-      options.bytes = buffer.byteLength;
-    }
-    return Scheduler.post(
-      "File_prototype_write",
-      [this._fdmsg, Type.void_t.in_ptr.toMsg(buffer), options],
-      buffer /* Ensure that |buffer| is not gc-ed*/
-    );
-  },
-
-  /**
-   * Read bytes from this file to a new buffer.
-   *
-   * @param {number=} bytes If unspecified, read all the remaining bytes from
-   * this file. If specified, read |bytes| bytes, or less if the file does not
-   * contain that many bytes.
-   * @param {JSON} options
-   * @return {promise}
-   * @resolves {Uint8Array} An array containing the bytes read.
-   */
-  read: function read(nbytes, options = {}) {
-    let promise = Scheduler.post("File_prototype_read", [
-      this._fdmsg,
-      nbytes,
-      options,
-    ]);
-    return promise.then(function onSuccess(data) {
-      return new Uint8Array(data.buffer, data.byteOffset, data.byteLength);
-    });
-  },
-
-  /**
-   * Return the current position in the file, as bytes.
-   *
-   * @return {promise}
-   * @resolves {number} The current position in the file,
-   * as a number of bytes since the start of the file.
-   */
-  getPosition: function getPosition() {
-    return Scheduler.post("File_prototype_getPosition", [this._fdmsg]);
-  },
-
-  /**
-   * Set the current position in the file, as bytes.
-   *
-   * @param {number} pos A number of bytes.
-   * @param {number} whence The reference position in the file,
-   * which may be either POS_START (from the start of the file),
-   * POS_END (from the end of the file) or POS_CUR (from the
-   * current position in the file).
-   *
-   * @return {promise}
-   */
-  setPosition: function setPosition(pos, whence) {
-    return Scheduler.post("File_prototype_setPosition", [
-      this._fdmsg,
-      pos,
-      whence,
-    ]);
-  },
-
-  /**
-   * Flushes the file's buffers and causes all buffered data
-   * to be written.
-   * Disk flushes are very expensive and therefore should be used carefully,
-   * sparingly and only in scenarios where it is vital that data survives
-   * system crashes. Even though the function will be executed off the
-   * main-thread, it might still affect the overall performance of any running
-   * application.
-   *
-   * @return {promise}
-   */
-  flush: function flush() {
-    return Scheduler.post("File_prototype_flush", [this._fdmsg]);
-  },
-
-  /**
-   * Set the file's access permissions.  This does nothing on Windows.
-   *
-   * This operation is likely to fail if applied to a file that was
-   * not created by the currently running program (more precisely,
-   * if it was created by a program running under a different OS-level
-   * user account).  It may also fail, or silently do nothing, if the
-   * filesystem containing the file does not support access permissions.
-   *
-   * @param {*=} options Object specifying the requested permissions:
-   *
-   * - {number} unixMode The POSIX file mode to set on the file.  If omitted,
-   *  the POSIX file mode is reset to the default used by |OS.file.open|.  If
-   *  specified, the permissions will respect the process umask as if they
-   *  had been specified as arguments of |OS.File.open|, unless the
-   *  |unixHonorUmask| parameter tells otherwise.
-   * - {bool} unixHonorUmask If omitted or true, any |unixMode| value is
-   *  modified by the process umask, as |OS.File.open| would have done.  If
-   *  false, the exact value of |unixMode| will be applied.
-   */
-  setPermissions: function setPermissions(options = {}) {
-    return Scheduler.post("File_prototype_setPermissions", [
-      this._fdmsg,
-      options,
-    ]);
-  },
-};
-
-if (SharedAll.Constants.Sys.Name != "Android") {
-  /**
-   * Set the last access and modification date of the file.
-   * The time stamp resolution is 1 second at best, but might be worse
-   * depending on the platform.
-   *
-   * WARNING: This method is not implemented on Android/B2G. On Android/B2G,
-   * you should use File.setDates instead.
-   *
-   * @return {promise}
-   * @rejects {TypeError}
-   * @rejects {OS.File.Error}
-   */
-  File.prototype.setDates = function(accessDate, modificationDate) {
-    return Scheduler.post(
-      "File_prototype_setDates",
-      [this._fdmsg, accessDate, modificationDate],
-      this
-    );
-  };
-}
-
-/**
- * Open a file asynchronously.
- *
- * @return {promise}
- * @resolves {OS.File}
- * @rejects {OS.Error}
- */
-File.open = function open(path, mode, options) {
-  return Scheduler.post(
-    "open",
-    [Type.path.toMsg(path), mode, options],
-    path
-  ).then(function onSuccess(msg) {
-    return new File(msg);
-  });
-};
-
-/**
- * Creates and opens a file with a unique name. By default, generate a random HEX number and use it to create a unique new file name.
- *
- * @param {string} path The path to the file.
- * @param {*=} options Additional options for file opening. This
- * implementation interprets the following fields:
- *
- * - {number} humanReadable If |true|, create a new filename appending a decimal number. ie: filename-1.ext, filename-2.ext.
- *  If |false| use HEX numbers ie: filename-A65BC0.ext
- * - {number} maxReadableNumber Used to limit the amount of tries after a failed
- *  file creation. Default is 20.
- *
- * @return {Object} contains A file object{file} and the path{path}.
- * @throws {OS.File.Error} If the file could not be opened.
- */
-File.openUnique = function openUnique(path, options) {
-  return Scheduler.post(
-    "openUnique",
-    [Type.path.toMsg(path), options],
-    path
-  ).then(function onSuccess(msg) {
-    return {
-      path: msg.path,
-      file: new File(msg.file),
-    };
-  });
-};
-
-/**
- * Get the information on the file.
- *
- * @return {promise}
- * @resolves {OS.File.Info}
- * @rejects {OS.Error}
- */
-File.stat = function stat(path, options) {
-  return Scheduler.post("stat", [Type.path.toMsg(path), options], path).then(
-    File.Info.fromMsg
-  );
-};
-
-/**
- * Set the last access and modification date of the file.
- * The time stamp resolution is 1 second at best, but might be worse
- * depending on the platform.
- *
- * @return {promise}
- * @rejects {TypeError}
- * @rejects {OS.File.Error}
- */
-File.setDates = function setDates(path, accessDate, modificationDate) {
-  return Scheduler.post(
-    "setDates",
-    [Type.path.toMsg(path), accessDate, modificationDate],
-    this
-  );
-};
-
-/**
- * Set the file's access permissions.  This does nothing on Windows.
- *
- * This operation is likely to fail if applied to a file that was
- * not created by the currently running program (more precisely,
- * if it was created by a program running under a different OS-level
- * user account).  It may also fail, or silently do nothing, if the
- * filesystem containing the file does not support access permissions.
- *
- * @param {string} path The path to the file.
- * @param {*=} options Object specifying the requested permissions:
- *
- * - {number} unixMode The POSIX file mode to set on the file.  If omitted,
- *  the POSIX file mode is reset to the default used by |OS.file.open|.  If
- *  specified, the permissions will respect the process umask as if they
- *  had been specified as arguments of |OS.File.open|, unless the
- *  |unixHonorUmask| parameter tells otherwise.
- * - {bool} unixHonorUmask If omitted or true, any |unixMode| value is
- *  modified by the process umask, as |OS.File.open| would have done.  If
- *  false, the exact value of |unixMode| will be applied.
- */
-File.setPermissions = function setPermissions(path, options = {}) {
-  return Scheduler.post("setPermissions", [Type.path.toMsg(path), options]);
-};
-
-/**
- * Fetch the current directory
- *
- * @return {promise}
- * @resolves {string} The current directory, as a path usable with OS.Path
- * @rejects {OS.Error}
- */
-File.getCurrentDirectory = function getCurrentDirectory() {
-  return Scheduler.post("getCurrentDirectory").then(Type.path.fromMsg);
-};
-
-/**
- * Copy a file to a destination.
- *
- * @param {string} sourcePath The platform-specific path at which
- * the file may currently be found.
- * @param {string} destPath The platform-specific path at which the
- * file should be copied.
- * @param {*=} options An object which may contain the following fields:
- *
- * @option {bool} noOverwrite - If true, this function will fail if
- * a file already exists at |destPath|. Otherwise, if this file exists,
- * it will be erased silently.
- *
- * @rejects {OS.File.Error} In case of any error.
- *
- * General note: The behavior of this function is defined only when
- * it is called on a single file. If it is called on a directory, the
- * behavior is undefined and may not be the same across all platforms.
- *
- * General note: The behavior of this function with respect to metadata
- * is unspecified. Metadata may or may not be copied with the file. The
- * behavior may not be the same across all platforms.
- */
-File.copy = function copy(sourcePath, destPath, options) {
-  return Scheduler.post(
-    "copy",
-    [Type.path.toMsg(sourcePath), Type.path.toMsg(destPath), options],
-    [sourcePath, destPath]
-  );
-};
-
-/**
- * Move a file to a destination.
- *
- * @param {string} sourcePath The platform-specific path at which
- * the file may currently be found.
- * @param {string} destPath The platform-specific path at which the
- * file should be moved.
- * @param {*=} options An object which may contain the following fields:
- *
- * @option {bool} noOverwrite - If set, this function will fail if
- * a file already exists at |destPath|. Otherwise, if this file exists,
- * it will be erased silently.
- *
- * @returns {Promise}
- * @rejects {OS.File.Error} In case of any error.
- *
- * General note: The behavior of this function is defined only when
- * it is called on a single file. If it is called on a directory, the
- * behavior is undefined and may not be the same across all platforms.
- *
- * General note: The behavior of this function with respect to metadata
- * is unspecified. Metadata may or may not be moved with the file. The
- * behavior may not be the same across all platforms.
- */
-File.move = function move(sourcePath, destPath, options) {
-  return Scheduler.post(
-    "move",
-    [Type.path.toMsg(sourcePath), Type.path.toMsg(destPath), options],
-    [sourcePath, destPath]
-  );
-};
-
-/**
- * Create a symbolic link to a source.
- *
- * @param {string} sourcePath The platform-specific path to which
- * the symbolic link should point.
- * @param {string} destPath The platform-specific path at which the
- * symbolic link should be created.
- *
- * @returns {Promise}
- * @rejects {OS.File.Error} In case of any error.
- */
-if (!SharedAll.Constants.Win) {
-  File.unixSymLink = function unixSymLink(sourcePath, destPath) {
-    return Scheduler.post(
-      "unixSymLink",
-      [Type.path.toMsg(sourcePath), Type.path.toMsg(destPath)],
-      [sourcePath, destPath]
-    );
-  };
-}
-
-/**
- * Remove an empty directory.
- *
- * @param {string} path The name of the directory to remove.
- * @param {*=} options Additional options.
- *   - {bool} ignoreAbsent If |true|, do not fail if the
- *     directory does not exist yet.
- */
-File.removeEmptyDir = function removeEmptyDir(path, options) {
-  return Scheduler.post(
-    "removeEmptyDir",
-    [Type.path.toMsg(path), options],
-    path
-  );
-};
-
-/**
- * Remove an existing file.
- *
- * @param {string} path The name of the file.
- * @param {*=} options Additional options.
- *   - {bool} ignoreAbsent If |false|, throw an error if the file does
- *     not exist. |true| by default.
- *
- * @throws {OS.File.Error} In case of I/O error.
- */
-File.remove = function remove(path, options) {
-  return Scheduler.post("remove", [Type.path.toMsg(path), options], path);
-};
-
-/**
- * Create a directory and, optionally, its parent directories.
- *
- * @param {string} path The name of the directory.
- * @param {*=} options Additional options.
- *
- * - {string} from If specified, the call to |makeDir| creates all the
- * ancestors of |path| that are descendants of |from|. Note that |path|
- * must be a descendant of |from|, and that |from| and its existing
- * subdirectories present in |path|  must be user-writeable.
- * Example:
- *   makeDir(Path.join(profileDir, "foo", "bar"), { from: profileDir });
- *  creates directories profileDir/foo, profileDir/foo/bar
- * - {bool} ignoreExisting If |false|, throw an error if the directory
- * already exists. |true| by default. Ignored if |from| is specified.
- * - {number} unixMode Under Unix, if specified, a file creation mode,
- * as per libc function |mkdir|. If unspecified, dirs are
- * created with a default mode of 0700 (dir is private to
- * the user, the user can read, write and execute). Ignored under Windows
- * or if the file system does not support file creation modes.
- * - {C pointer} winSecurity Under Windows, if specified, security
- * attributes as per winapi function |CreateDirectory|. If
- * unspecified, use the default security descriptor, inherited from
- * the parent directory. Ignored under Unix or if the file system
- * does not support security descriptors.
- */
-File.makeDir = function makeDir(path, options) {
-  return Scheduler.post("makeDir", [Type.path.toMsg(path), options], path);
-};
-
-/**
- * Return the contents of a file
- *
- * @param {string} path The path to the file.
- * @param {number=} bytes Optionally, an upper bound to the number of bytes
- * to read. DEPRECATED - please use options.bytes instead.
- * @param {JSON} options Additional options.
- * - {boolean} sequential A flag that triggers a population of the page cache
- * with data from a file so that subsequent reads from that file would not
- * block on disk I/O. If |true| or unspecified, inform the system that the
- * contents of the file will be read in order. Otherwise, make no such
- * assumption. |true| by default.
- * - {number} bytes An upper bound to the number of bytes to read.
- * - {string} compression If "lz4" and if the file is compressed using the lz4
- * compression algorithm, decompress the file contents on the fly.
- *
- * @resolves {Uint8Array} A buffer holding the bytes
- * read from the file.
- */
-File.read = function read(path, bytes, options = {}) {
-  if (typeof bytes == "object") {
-    // Passing |bytes| as an argument is deprecated.
-    // We should now be passing it as a field of |options|.
-    options = bytes || {};
-  } else {
-    options = clone(options, [
-      "outExecutionDuration",
-      "outSerializationDuration",
-    ]);
-    if (typeof bytes != "undefined") {
-      options.bytes = bytes;
-    }
-  }
-
-  if (options.compression || !nativeWheneverAvailable) {
-    // We need to use the JS implementation.
-    let promise = Scheduler.post(
-      "read",
-      [Type.path.toMsg(path), bytes, options],
-      path
-    );
-    return promise.then(function onSuccess(data) {
-      if (typeof data == "string") {
-        return data;
-      }
-      return new Uint8Array(data.buffer, data.byteOffset, data.byteLength);
-    });
-  }
-
-  // Otherwise, use the native implementation.
-  return Scheduler.push(() => Native.read(path, options));
-};
-
-/**
- * Find outs if a file exists.
- *
- * @param {string} path The path to the file.
- *
- * @return {bool} true if the file exists, false otherwise.
- */
-File.exists = function exists(path) {
-  return Scheduler.post("exists", [Type.path.toMsg(path)], path);
-};
-
-/**
- * Write a file, atomically.
- *
- * By opposition to a regular |write|, this operation ensures that,
- * until the contents are fully written, the destination file is
- * not modified.
- *
- * Limitation: In a few extreme cases (hardware failure during the
- * write, user unplugging disk during the write, etc.), data may be
- * corrupted. If your data is user-critical (e.g. preferences,
- * application data, etc.), you may wish to consider adding options
- * |tmpPath| and/or |flush| to reduce the likelihood of corruption, as
- * detailed below. Note that no combination of options can be
- * guaranteed to totally eliminate the risk of corruption.
- *
- * @param {string} path The path of the file to modify.
- * @param {Typed Array | C pointer} buffer A buffer containing the bytes to write.
- * @param {*=} options Optionally, an object determining the behavior
- * of this function. This object may contain the following fields:
- * - {number} bytes The number of bytes to write. If unspecified,
- * |buffer.byteLength|. Required if |buffer| is a C pointer.
- * - {string} tmpPath If |null| or unspecified, write all data directly
- * to |path|. If specified, write all data to a temporary file called
- * |tmpPath| and, once this write is complete, rename the file to
- * replace |path|. Performing this additional operation is a little
- * slower but also a little safer.
- * - {bool} noOverwrite - If set, this function will fail if a file already
- * exists at |path|.
- * - {bool} flush - If |false| or unspecified, return immediately once the
- * write is complete. If |true|, before writing, force the operating system
- * to write its internal disk buffers to the disk. This is considerably slower
- * (not just for the application but for the whole system) but also safer:
- * if the system shuts down improperly (typically due to a kernel freeze
- * or a power failure) or if the device is disconnected before the buffer
- * is flushed, the file has more chances of not being corrupted.
- * - {string} backupTo - If specified, backup the destination file as |backupTo|.
- * Note that this function renames the destination file before overwriting it.
- * If the process or the operating system freezes or crashes
- * during the short window between these operations,
- * the destination file will have been moved to its backup.
- *
- * @return {promise}
- * @resolves {number} The number of bytes actually written.
- */
-File.writeAtomic = function writeAtomic(path, buffer, options = {}) {
-  const useNativeImplementation =
-    nativeWheneverAvailable &&
-    !options.compression &&
-    !(isTypedArray(buffer) && "byteOffset" in buffer && buffer.byteOffset > 0);
-  // Copy |options| to avoid modifying the original object but preserve the
-  // reference to |outExecutionDuration|, |outSerializationDuration| option if it is passed.
-  options = clone(options, [
-    "outExecutionDuration",
-    "outSerializationDuration",
-  ]);
-  // As options.tmpPath is a path, we need to encode it as |Type.path| message, but only
-  // if we are not using the native implementation.
-  if ("tmpPath" in options && !useNativeImplementation) {
-    options.tmpPath = Type.path.toMsg(options.tmpPath);
-  }
-  if (isTypedArray(buffer) && !("bytes" in options)) {
-    options.bytes = buffer.byteLength;
-  }
-  let refObj = {};
-  let promise;
-  TelemetryStopwatch.start("OSFILE_WRITEATOMIC_JANK_MS", refObj);
-  if (useNativeImplementation) {
-    promise = Scheduler.push(() => Native.writeAtomic(path, buffer, options));
-  } else {
-    promise = Scheduler.post(
-      "writeAtomic",
-      [Type.path.toMsg(path), Type.void_t.in_ptr.toMsg(buffer), options],
-      [options, buffer, path]
-    );
-  }
-  TelemetryStopwatch.finish("OSFILE_WRITEATOMIC_JANK_MS", refObj);
-  return promise;
-};
-
-File.removeDir = function(path, options = {}) {
-  return Scheduler.post("removeDir", [Type.path.toMsg(path), options], path);
-};
-
-/**
- * Information on a file, as returned by OS.File.stat or
- * OS.File.prototype.stat
- *
- * @constructor
- */
-File.Info = function Info(value) {
-  // Note that we can't just do this[k] = value[k] because our
-  // prototype defines getters for all of these fields.
-  for (let k in value) {
-    Object.defineProperty(this, k, { value: value[k] });
-  }
-};
-File.Info.prototype = SysAll.AbstractInfo.prototype;
-
-File.Info.fromMsg = function fromMsg(value) {
-  return new File.Info(value);
-};
-
-/**
- * Get worker's current DEBUG flag.
- * Note: This is used for testing purposes.
- */
-File.GET_DEBUG = function GET_DEBUG() {
-  return Scheduler.post("GET_DEBUG");
-};
-
-/**
- * Iterate asynchronously through a directory
- *
- * @constructor
- */
-var DirectoryIterator = function DirectoryIterator(path, options) {
-  /**
-   * Open the iterator on the worker thread
-   *
-   * @type {Promise}
-   * @resolves {*} A message accepted by the methods of DirectoryIterator
-   * in the worker thread
-   */
-  this._itmsg = Scheduler.post(
-    "new_DirectoryIterator",
-    [Type.path.toMsg(path), options],
-    path
-  );
-  this._isClosed = false;
-};
-DirectoryIterator.prototype = {
-  [Symbol.asyncIterator]() {
-    return this;
-  },
-
-  _itmsg: null,
-
-  /**
-   * Determine whether the directory exists.
-   *
-   * @resolves {boolean}
-   */
-  async exists() {
-    if (this._isClosed) {
-      return Promise.resolve(false);
-    }
-    let iterator = await this._itmsg;
-    return Scheduler.post("DirectoryIterator_prototype_exists", [iterator]);
-  },
-  /**
-   * Get the next entry in the directory.
-   *
-   * @return {Promise}
-   * @resolves By definition of the async iterator protocol, either
-   * `{value: {File.Entry}, done: false}` if there is an unvisited entry
-   * in the directory, or `{value: undefined, done: true}`, otherwise.
-   */
-  async next() {
-    if (this._isClosed) {
-      return { value: undefined, done: true };
-    }
-    return this._next(await this._itmsg);
-  },
-  /**
-   * Get several entries at once.
-   *
-   * @param {number=} length If specified, the number of entries
-   * to return. If unspecified, return all remaining entries.
-   * @return {Promise}
-   * @resolves {Array} An array containing the |length| next entries.
-   */
-  async nextBatch(size) {
-    if (this._isClosed) {
-      return [];
-    }
-    let iterator = await this._itmsg;
-    let array = await Scheduler.post("DirectoryIterator_prototype_nextBatch", [
-      iterator,
-      size,
-    ]);
-    return array.map(DirectoryIterator.Entry.fromMsg);
-  },
-  /**
-   * Apply a function to all elements of the directory sequentially.
-   *
-   * @param {Function} cb This function will be applied to all entries
-   * of the directory. It receives as arguments
-   *  - the OS.File.Entry corresponding to the entry;
-   *  - the index of the entry in the enumeration;
-   *  - the iterator itself - return |iterator.close()| to stop the loop.
-   *
-   * If the callback returns a promise, iteration waits until the
-   * promise is resolved before proceeding.
-   *
-   * @return {Promise} A promise resolved once the loop has reached
-   * its end.
-   */
-  async forEach(cb, options) {
-    if (this._isClosed) {
-      return undefined;
-    }
-    let position = 0;
-    let iterator = await this._itmsg;
-    while (true) {
-      if (this._isClosed) {
-        return undefined;
-      }
-      let { value, done } = await this._next(iterator);
-      if (done) {
-        return undefined;
-      }
-      await cb(value, position++, this);
-    }
-  },
-  /**
-   * Auxiliary method: fetch the next item
-   *
-   * @resolves `{value: undefined, done: true}` If all entries have already
-   * been visited or the iterator has been closed.
-   */
-  async _next(iterator) {
-    if (this._isClosed) {
-      return { value: undefined, done: true };
-    }
-    let {
-      value,
-      done,
-    } = await Scheduler.post("DirectoryIterator_prototype_next", [iterator]);
-    if (done) {
-      this.close();
-      return { value: undefined, done: true };
-    }
-    return { value: DirectoryIterator.Entry.fromMsg(value), done: false };
-  },
-  /**
-   * Close the iterator
-   */
-  async close() {
-    if (this._isClosed) {
-      return undefined;
-    }
-    this._isClosed = true;
-    let iterator = this._itmsg;
-    this._itmsg = null;
-    return Scheduler.post("DirectoryIterator_prototype_close", [iterator]);
-  },
-};
-
-DirectoryIterator.Entry = function Entry(value) {
-  return value;
-};
-DirectoryIterator.Entry.prototype = Object.create(
-  SysAll.AbstractEntry.prototype
-);
-
-DirectoryIterator.Entry.fromMsg = function fromMsg(value) {
-  return new DirectoryIterator.Entry(value);
-};
-
-File.resetWorker = function() {
-  return (async function() {
-    let resources = await Scheduler.kill({ shutdown: false, reset: true });
-    if (resources && !resources.killed) {
-      throw new Error(
-        "Could not reset worker, this would leak file descriptors: " +
-          JSON.stringify(resources)
-      );
-    }
-  })();
-};
-
-// Constants
-File.POS_START = SysAll.POS_START;
-File.POS_CURRENT = SysAll.POS_CURRENT;
-File.POS_END = SysAll.POS_END;
-
-// Exports
-File.Error = OSError;
-File.DirectoryIterator = DirectoryIterator;
-
-var OS = {};
-OS.File = File;
-OS.Constants = SharedAll.Constants;
-OS.Shared = {
-  LOG: SharedAll.LOG,
-  Type: SysAll.Type,
-  get DEBUG() {
-    return SharedAll.Config.DEBUG;
-  },
-  set DEBUG(x) {
-    SharedAll.Config.DEBUG = x;
-  },
-};
-Object.freeze(OS.Shared);
-OS.Path = Path;
-
-// Returns a resolved promise when all the queued operation have been completed.
-Object.defineProperty(OS.File, "queue", {
-  get() {
-    return Scheduler.queue;
-  },
-});
-
-// `true` if this is a content process, `false` otherwise.
-// It would be nicer to go through `Services.appinfo`, but some tests need to be
-// able to replace that field with a custom implementation before it is first
-// called.
-const isContent =
-  // eslint-disable-next-line mozilla/use-services
-  Cc["@mozilla.org/xre/app-info;1"].getService(Ci.nsIXULRuntime).processType ==
-  Ci.nsIXULRuntime.PROCESS_TYPE_CONTENT;
-
-/**
- * Shutdown barriers, to let clients register to be informed during shutdown.
- */
-var Barriers = {
-  shutdown: new AsyncShutdown.Barrier(
-    "OS.File: Waiting for clients before full shutdown"
-  ),
-  /**
-   * Return the shutdown state of OS.File
-   */
-  getDetails() {
-    let result = {
-      launched: Scheduler.launched,
-      shutdown: Scheduler.shutdown,
-      worker: !!Scheduler._worker,
-      pendingReset: !!Scheduler.resetTimer,
-      latestSent: Scheduler.Debugging.latestSent,
-      latestReceived: Scheduler.Debugging.latestReceived,
-      messagesSent: Scheduler.Debugging.messagesSent,
-      messagesReceived: Scheduler.Debugging.messagesReceived,
-      messagesQueued: Scheduler.Debugging.messagesQueued,
-      DEBUG: SharedAll.Config.DEBUG,
-    };
-    // Convert dates to strings for better readability
-    for (let key of ["latestSent", "latestReceived"]) {
-      if (result[key] && typeof result[key][0] == "number") {
-        result[key][0] = Date(result[key][0]);
-      }
-    }
-    return result;
-  },
-};
-
-function setupShutdown(phaseName) {
-  Barriers[phaseName] = new AsyncShutdown.Barrier(
-    `OS.File: Waiting for clients before ${phaseName}`
-  );
-  File[phaseName] = Barriers[phaseName].client;
-
-  // Auto-flush OS.File during `phaseName`. This ensures that any I/O
-  // that has been queued *before* `phaseName` is properly completed.
-  // To ensure that I/O queued *during* `phaseName` change is completed,
-  // clients should register using AsyncShutdown.addBlocker.
-  AsyncShutdown[phaseName].addBlocker(
-    `OS.File: flush I/O queued before ${phaseName}`,
-    async function() {
-      // Give clients a last chance to enqueue requests.
-      await Barriers[phaseName].wait({ crashAfterMS: null });
-
-      // Wait until all currently enqueued requests are completed.
-      await Scheduler.queue;
-    },
-    () => {
-      let details = Barriers.getDetails();
-      details.clients = Barriers[phaseName].state;
-      return details;
-    }
-  );
-}
-
-// profile-before-change only exists in the parent, and OS.File should
-// not be used in the child process anyways.
-if (!isContent) {
-  setupShutdown("profileBeforeChange");
-}
-File.shutdown = Barriers.shutdown.client;