--- a/browser/app/profile/firefox.js
+++ b/browser/app/profile/firefox.js
@@ -1192,16 +1192,18 @@ pref("services.sync.prefs.sync.privacy.c
 pref("services.sync.prefs.sync.privacy.clearOnShutdown.cookies", true);
 pref("services.sync.prefs.sync.privacy.clearOnShutdown.downloads", true);
 pref("services.sync.prefs.sync.privacy.clearOnShutdown.formdata", true);
 pref("services.sync.prefs.sync.privacy.clearOnShutdown.history", true);
 pref("services.sync.prefs.sync.privacy.clearOnShutdown.offlineApps", true);
 pref("services.sync.prefs.sync.privacy.clearOnShutdown.sessions", true);
 pref("services.sync.prefs.sync.privacy.clearOnShutdown.siteSettings", true);
 pref("services.sync.prefs.sync.privacy.donottrackheader.enabled", true);
+pref("services.sync.prefs.sync.privacy.fuzzyfox.enabled", true);
+pref("services.sync.prefs.sync.privacy.fuzzyfox.clockgrainus", true);
 pref("services.sync.prefs.sync.privacy.sanitize.sanitizeOnShutdown", true);
 pref("services.sync.prefs.sync.privacy.trackingprotection.enabled", true);
 pref("services.sync.prefs.sync.privacy.trackingprotection.pbmode.enabled", true);
 pref("services.sync.prefs.sync.privacy.resistFingerprinting", true);
 pref("services.sync.prefs.sync.privacy.reduceTimerPrecision", true);
 pref("services.sync.prefs.sync.privacy.resistFingerprinting.reduceTimerPrecision.microseconds", true);
 pref("services.sync.prefs.sync.privacy.resistFingerprinting.reduceTimerPrecision.jitter", true);
 pref("services.sync.prefs.sync.security.OCSP.enabled", true);

--- a/browser/config/mozconfigs/linux64/code-coverage-debug
+++ b/browser/config/mozconfigs/linux64/code-coverage-debug
@@ -1,3 +1,5 @@
 . "$topsrcdir/browser/config/mozconfigs/linux64/code-coverage"
 
 ac_add_options --enable-debug=-g1
+# We enable Rust tests on the debug build only, as the opt build is currently only used for fuzzing.
+ac_add_options --enable-rust-tests

--- a/browser/config/mozconfigs/win64/code-coverage
+++ b/browser/config/mozconfigs/win64/code-coverage
@@ -3,16 +3,17 @@ MOZ_AUTOMATION_L10N_CHECK=0
 . "$topsrcdir/browser/config/mozconfigs/common"
 . "$topsrcdir/browser/config/mozconfigs/win64/common-win64"
 
 ac_add_options --enable-optimize
 ac_add_options --enable-debug
 ac_add_options --disable-sandbox
 ac_add_options --disable-warnings-as-errors
 ac_add_options --enable-coverage
+ac_add_options --enable-rust-tests
 
 # Needed to enable breakpad in application.ini
 export MOZILLA_OFFICIAL=1
 
 # Enable Telemetry
 export MOZ_TELEMETRY_REPORTING=1
 
 . $topsrcdir/build/win64/mozconfig.vs-latest

--- a/browser/extensions/pdfjs/README.mozilla
+++ b/browser/extensions/pdfjs/README.mozilla
@@ -1,5 +1,5 @@
 This is the PDF.js project output, https://github.com/mozilla/pdf.js
 
-Current extension version is: 2.0.936
+Current extension version is: 2.0.943
 
-Taken from upstream commit: d2189293
+Taken from upstream commit: dc98bf76

--- a/browser/extensions/pdfjs/content/build/pdf.js
+++ b/browser/extensions/pdfjs/content/build/pdf.js
@@ -118,18 +118,18 @@ return /******/ (function(modules) { // 
 /************************************************************************/
 /******/ ([
 /* 0 */
 /***/ (function(module, exports, __w_pdfjs_require__) {
 
 "use strict";
 
 
-var pdfjsVersion = '2.0.936';
-var pdfjsBuild = 'd2189293';
+var pdfjsVersion = '2.0.943';
+var pdfjsBuild = 'dc98bf76';
 var pdfjsSharedUtil = __w_pdfjs_require__(1);
 var pdfjsDisplayAPI = __w_pdfjs_require__(7);
 var pdfjsDisplayTextLayer = __w_pdfjs_require__(19);
 var pdfjsDisplayAnnotationLayer = __w_pdfjs_require__(20);
 var pdfjsDisplayDOMUtils = __w_pdfjs_require__(8);
 var pdfjsDisplaySVG = __w_pdfjs_require__(21);
 let pdfjsDisplayWorkerOptions = __w_pdfjs_require__(13);
 let pdfjsDisplayAPICompatibility = __w_pdfjs_require__(10);
@@ -4221,17 +4221,17 @@ function _fetchDocument(worker, source, 
     return Promise.reject(new Error('Worker was destroyed'));
   }
   if (pdfDataRangeTransport) {
     source.length = pdfDataRangeTransport.length;
     source.initialData = pdfDataRangeTransport.initialData;
   }
   return worker.messageHandler.sendWithPromise('GetDocRequest', {
     docId,
-    apiVersion: '2.0.936',
+    apiVersion: '2.0.943',
     source: {
       data: source.data,
       url: source.url,
       password: source.password,
       disableAutoFetch: source.disableAutoFetch,
       rangeChunkSize: source.rangeChunkSize,
       length: source.length
     },
@@ -4278,67 +4278,61 @@ var PDFDocumentLoadingTask = function PD
       });
     },
     then: function PDFDocumentLoadingTask_then(onFulfilled, onRejected) {
       return this.promise.then.apply(this.promise, arguments);
     }
   };
   return PDFDocumentLoadingTask;
 }();
-var PDFDataRangeTransport = function pdfDataRangeTransportClosure() {
-  function PDFDataRangeTransport(length, initialData) {
+class PDFDataRangeTransport {
+  constructor(length, initialData) {
     this.length = length;
     this.initialData = initialData;
     this._rangeListeners = [];
     this._progressListeners = [];
     this._progressiveReadListeners = [];
     this._readyCapability = (0, _util.createPromiseCapability)();
   }
-  PDFDataRangeTransport.prototype = {
-    addRangeListener: function PDFDataRangeTransport_addRangeListener(listener) {
-      this._rangeListeners.push(listener);
-    },
-    addProgressListener: function PDFDataRangeTransport_addProgressListener(listener) {
-      this._progressListeners.push(listener);
-    },
-    addProgressiveReadListener: function PDFDataRangeTransport_addProgressiveReadListener(listener) {
-      this._progressiveReadListeners.push(listener);
-    },
-    onDataRange: function PDFDataRangeTransport_onDataRange(begin, chunk) {
-      var listeners = this._rangeListeners;
-      for (var i = 0, n = listeners.length; i < n; ++i) {
-        listeners[i](begin, chunk);
-      }
-    },
-    onDataProgress: function PDFDataRangeTransport_onDataProgress(loaded) {
-      this._readyCapability.promise.then(() => {
-        var listeners = this._progressListeners;
-        for (var i = 0, n = listeners.length; i < n; ++i) {
-          listeners[i](loaded);
-        }
-      });
-    },
-    onDataProgressiveRead: function PDFDataRangeTransport_onDataProgress(chunk) {
-      this._readyCapability.promise.then(() => {
-        var listeners = this._progressiveReadListeners;
-        for (var i = 0, n = listeners.length; i < n; ++i) {
-          listeners[i](chunk);
-        }
-      });
-    },
-    transportReady: function PDFDataRangeTransport_transportReady() {
-      this._readyCapability.resolve();
-    },
-    requestDataRange: function PDFDataRangeTransport_requestDataRange(begin, end) {
-      (0, _util.unreachable)('Abstract method PDFDataRangeTransport.requestDataRange');
-    },
-    abort: function PDFDataRangeTransport_abort() {}
-  };
-  return PDFDataRangeTransport;
-}();
+  addRangeListener(listener) {
+    this._rangeListeners.push(listener);
+  }
+  addProgressListener(listener) {
+    this._progressListeners.push(listener);
+  }
+  addProgressiveReadListener(listener) {
+    this._progressiveReadListeners.push(listener);
+  }
+  onDataRange(begin, chunk) {
+    for (const listener of this._rangeListeners) {
+      listener(begin, chunk);
+    }
+  }
+  onDataProgress(loaded) {
+    this._readyCapability.promise.then(() => {
+      for (const listener of this._progressListeners) {
+        listener(loaded);
+      }
+    });
+  }
+  onDataProgressiveRead(chunk) {
+    this._readyCapability.promise.then(() => {
+      for (const listener of this._progressiveReadListeners) {
+        listener(chunk);
+      }
+    });
+  }
+  transportReady() {
+    this._readyCapability.resolve();
+  }
+  requestDataRange(begin, end) {
+    (0, _util.unreachable)('Abstract method PDFDataRangeTransport.requestDataRange');
+  }
+  abort() {}
+}
 class PDFDocumentProxy {
   constructor(pdfInfo, transport, loadingTask) {
     this.loadingTask = loadingTask;
     this._pdfInfo = pdfInfo;
     this._transport = transport;
   }
   get numPages() {
     return this._pdfInfo.numPages;
@@ -5556,18 +5550,18 @@ var InternalRenderTask = function Intern
         }
       });
     }
   };
   return InternalRenderTask;
 }();
 var version, build;
 {
-  exports.version = version = '2.0.936';
-  exports.build = build = 'd2189293';
+  exports.version = version = '2.0.943';
+  exports.build = build = 'dc98bf76';
 }
 exports.getDocument = getDocument;
 exports.LoopbackPort = LoopbackPort;
 exports.PDFDataRangeTransport = PDFDataRangeTransport;
 exports.PDFWorker = PDFWorker;
 exports.PDFDocumentProxy = PDFDocumentProxy;
 exports.PDFPageProxy = PDFPageProxy;
 exports.setPDFNetworkStreamFactory = setPDFNetworkStreamFactory;

--- a/browser/extensions/pdfjs/content/build/pdf.worker.js
+++ b/browser/extensions/pdfjs/content/build/pdf.worker.js
@@ -118,18 +118,18 @@ return /******/ (function(modules) { // 
 /************************************************************************/
 /******/ ([
 /* 0 */
 /***/ (function(module, exports, __w_pdfjs_require__) {
 
 "use strict";
 
 
-var pdfjsVersion = '2.0.936';
-var pdfjsBuild = 'd2189293';
+var pdfjsVersion = '2.0.943';
+var pdfjsBuild = 'dc98bf76';
 var pdfjsCoreWorker = __w_pdfjs_require__(1);
 exports.WorkerMessageHandler = pdfjsCoreWorker.WorkerMessageHandler;
 
 /***/ }),
 /* 1 */
 /***/ (function(module, exports, __w_pdfjs_require__) {
 
 "use strict";
@@ -322,17 +322,17 @@ var WorkerMessageHandler = {
     });
   },
   createDocumentHandler(docParams, port) {
     var pdfManager;
     var terminated = false;
     var cancelXHRs = null;
     var WorkerTasks = [];
     let apiVersion = docParams.apiVersion;
-    let workerVersion = '2.0.936';
+    let workerVersion = '2.0.943';
     if (apiVersion !== workerVersion) {
       throw new Error(`The API version "${apiVersion}" does not match ` + `the Worker version "${workerVersion}".`);
     }
     var docId = docParams.docId;
     var docBaseUrl = docParams.docBaseUrl;
     var workerHandlerName = docParams.docId + '_worker';
     var handler = new _message_handler.MessageHandler(workerHandlerName, docId, port);
     handler.postMessageTransfers = docParams.postMessageTransfers;

--- a/browser/extensions/pdfjs/content/web/viewer.js
+++ b/browser/extensions/pdfjs/content/web/viewer.js
@@ -9008,29 +9008,27 @@ class MozL10n {
       highlightAll: !!detail.highlightAll,
       findPrevious: !!detail.findPrevious
     });
   };
   for (let event of events) {
     window.addEventListener(event, handleEvent);
   }
 })();
-function FirefoxComDataRangeTransport(length, initialData) {
-  _pdfjsLib.PDFDataRangeTransport.call(this, length, initialData);
-}
-FirefoxComDataRangeTransport.prototype = Object.create(_pdfjsLib.PDFDataRangeTransport.prototype);
-FirefoxComDataRangeTransport.prototype.requestDataRange = function FirefoxComDataRangeTransport_requestDataRange(begin, end) {
-  FirefoxCom.request('requestDataRange', {
-    begin,
-    end
-  });
-};
-FirefoxComDataRangeTransport.prototype.abort = function FirefoxComDataRangeTransport_abort() {
-  FirefoxCom.requestSync('abortLoading', null);
-};
+class FirefoxComDataRangeTransport extends _pdfjsLib.PDFDataRangeTransport {
+  requestDataRange(begin, end) {
+    FirefoxCom.request('requestDataRange', {
+      begin,
+      end
+    });
+  }
+  abort() {
+    FirefoxCom.requestSync('abortLoading', null);
+  }
+}
 _app.PDFViewerApplication.externalServices = {
   updateFindControlState(data) {
     FirefoxCom.request('updateFindControlState', data);
   },
   updateFindMatchesCount(data) {
     FirefoxCom.request('updateFindMatchesCount', data);
   },
   initPassiveLoading(callbacks) {

--- a/browser/extensions/pdfjs/moz.yaml
+++ b/browser/extensions/pdfjs/moz.yaml
@@ -15,15 +15,15 @@ origin:
   description: Portable Document Format (PDF) viewer that is built with HTML5
 
   # Full URL for the package's homepage/etc
   # Usually different from repository url
   url: https://github.com/mozilla/pdf.js
 
   # Human-readable identifier for this version/release
   # Generally "version NNN", "tag SSS", "bookmark SSS"
-  release: version 2.0.936
+  release: version 2.0.943
 
   # The package's license, where possible using the mnemonic from
   # https://spdx.org/licenses/
   # Multiple licenses can be specified (as a YAML list)
   # A "LICENSE" file must exist containing the full license text
   license: Apache-2.0

--- a/config/external/ffi/moz.build
+++ b/config/external/ffi/moz.build
@@ -72,16 +72,18 @@ else:
     # Per-platform sources and flags.
     ffi_srcs = ()
     if CONFIG['FFI_TARGET'] == 'ARM':
         ffi_srcs = ('sysv.S', 'ffi.c')
         if CONFIG['CC_TYPE'] == 'clang':
             ASFLAGS += ['-no-integrated-as']
     elif CONFIG['FFI_TARGET'] == 'AARCH64':
         ffi_srcs = ('sysv.S', 'ffi.c')
+    elif CONFIG['FFI_TARGET'] == 'ARM64_WIN64':
+        ffi_srcs = ('win64.asm', 'ffi.c')
     elif CONFIG['FFI_TARGET'] == 'X86':
         ffi_srcs = ('ffi.c', 'sysv.S', 'win32.S')
     elif CONFIG['FFI_TARGET'] == 'X86_64':
         ffi_srcs = ('ffi64.c', 'unix64.S', 'ffi.c', 'sysv.S')
     elif CONFIG['FFI_TARGET'] == 'X86_WIN32':
         ffi_srcs = ['ffi.c']
         # MinGW Build for 32 bit
         if CONFIG['CC_TYPE'] in ('gcc', 'clang'):

--- a/dom/base/nsDeprecatedOperationList.h
+++ b/dom/base/nsDeprecatedOperationList.h
@@ -44,8 +44,9 @@ DEPRECATED_OPERATION(MixedDisplayObjectS
 DEPRECATED_OPERATION(MotionEvent)
 DEPRECATED_OPERATION(OrientationEvent)
 DEPRECATED_OPERATION(ProximityEvent)
 DEPRECATED_OPERATION(AmbientLightEvent)
 DEPRECATED_OPERATION(IDBOpenDBOptions_StorageType)
 DEPRECATED_OPERATION(DOMAttrModifiedEvent)
 DEPRECATED_OPERATION(MozBoxOrInlineBoxDisplay)
 DEPRECATED_OPERATION(DOMQuadBoundsAttr)
+DEPRECATED_OPERATION(CreateImageBitmapCanvasRenderingContext2D)

--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -10709,18 +10709,22 @@ public:
   {
   public:
     explicit Iterator(nsIDocument* aDoc, IteratorOption aOption)
       : mCurrent(PendingFullscreenChangeList::sList.getFirst())
       , mRootShellForIteration(aDoc->GetDocShell())
     {
       if (mCurrent) {
         if (mRootShellForIteration && aOption == eDocumentsWithSameRoot) {
+          // Use a temporary to avoid undefined behavior from passing
+          // mRootShellForIteration.
+          nsCOMPtr<nsIDocShellTreeItem> root;
           mRootShellForIteration->
-            GetRootTreeItem(getter_AddRefs(mRootShellForIteration));
+            GetRootTreeItem(getter_AddRefs(root));
+          mRootShellForIteration = root.forget();
         }
         SkipToNextMatch();
       }
     }
 
     UniquePtr<T> TakeAndNext()
     {
       auto thisChange = TakeAndNextInternal();
@@ -10746,17 +10750,19 @@ public:
           if (!docShell) {
             // Always automatically drop fullscreen changes which are
             // from a document detached from the doc shell.
             UniquePtr<T> change = TakeAndNextInternal();
             change->MayRejectPromise();
             continue;
           }
           while (docShell && docShell != mRootShellForIteration) {
-            docShell->GetParent(getter_AddRefs(docShell));
+            nsCOMPtr<nsIDocShellTreeItem> parent;
+            docShell->GetParent(getter_AddRefs(parent));
+            docShell = parent.forget();
           }
           if (docShell) {
             break;
           }
         }
         // The current one either don't have matched type, or isn't
         // inside the given subtree, so skip this item.
         mCurrent = mCurrent->getNext();

--- a/dom/canvas/ImageBitmap.cpp
+++ b/dom/canvas/ImageBitmap.cpp
@@ -1056,16 +1056,25 @@ ImageBitmap::CreateInternal(nsIGlobalObj
 
   return ret.forget();
 }
 
 /* static */ already_AddRefed<ImageBitmap>
 ImageBitmap::CreateInternal(nsIGlobalObject* aGlobal, CanvasRenderingContext2D& aCanvasCtx,
                             const Maybe<IntRect>& aCropRect, ErrorResult& aRv)
 {
+  nsCOMPtr<nsPIDOMWindowInner> win = do_QueryInterface(aGlobal);
+  nsGlobalWindowInner* window = nsGlobalWindowInner::Cast(win);
+  if (NS_WARN_IF(!window) || !window->GetExtantDoc()) {
+    aRv.Throw(NS_ERROR_DOM_SECURITY_ERR);
+    return nullptr;
+  }
+
+  window->GetExtantDoc()->WarnOnceAbout(nsIDocument::eCreateImageBitmapCanvasRenderingContext2D);
+
   // Check origin-clean.
   if (aCanvasCtx.GetCanvas()->IsWriteOnly()) {
     aRv.Throw(NS_ERROR_DOM_SECURITY_ERR);
     return nullptr;
   }
 
   RefPtr<SourceSurface> surface = aCanvasCtx.GetSurfaceSnapshot();
 

--- a/dom/canvas/WebGLContext.cpp
+++ b/dom/canvas/WebGLContext.cpp
@@ -596,26 +596,18 @@ WebGLContext::CreateAndInitGL(bool force
     // --
 
     typedef decltype(gl::GLContextProviderEGL::CreateOffscreen) fnCreateOffscreenT;
     const auto fnCreate = [&](fnCreateOffscreenT* const pfnCreateOffscreen,
                               const char* const info)
     {
         const gfx::IntSize dummySize(1, 1);
         nsCString failureId;
-        RefPtr<GLContext> gl = pfnCreateOffscreen(dummySize, surfaceCaps, flags,
-                                                  &failureId);
-        if (gl && gl->IsCoreProfile() &&
-            !(flags & gl::CreateContextFlags::REQUIRE_COMPAT_PROFILE) &&
-            !gl->IsSupported(gl::GLFeature::gpu_shader5))
-        {
-            // See comment on "constant-index-expression" in WebGLShaderValidator.cpp.
-            const auto compatFlags = flags | gl::CreateContextFlags::REQUIRE_COMPAT_PROFILE;
-            gl = pfnCreateOffscreen(dummySize, surfaceCaps, compatFlags, &failureId);
-        }
+        const RefPtr<GLContext> gl = pfnCreateOffscreen(dummySize, surfaceCaps, flags,
+                                                        &failureId);
         if (!gl) {
             out_failReasons->push_back(WebGLContext::FailureReason(failureId, info));
         }
         return gl;
     };
 
     const auto newGL = [&]() -> RefPtr<gl::GLContext> {
         if (tryNativeGL) {

--- a/dom/canvas/WebGLContextValidate.cpp
+++ b/dom/canvas/WebGLContextValidate.cpp
@@ -300,32 +300,33 @@ WebGLContext::ValidateUniformMatrixArray
     return true;
 }
 
 bool
 WebGLContext::InitAndValidateGL(FailureReason* const out_failReason)
 {
     MOZ_RELEASE_ASSERT(gl, "GFX: GL not initialized");
 
-    if (!gl->MakeCurrent(true)) {
-        MOZ_ASSERT(false);
-        *out_failReason = { "FEATURE_FAILURE_WEBGL_MAKECURRENT",
-                            "Failed to MakeCurrent for init." };
-        return false;
-    }
-
     // Unconditionally create a new format usage authority. This is
     // important when restoring contexts and extensions need to add
     // formats back into the authority.
     mFormatUsage = CreateFormatUsage(gl);
-    MOZ_RELEASE_ASSERT(mFormatUsage);
+    if (!mFormatUsage) {
+        *out_failReason = { "FEATURE_FAILURE_WEBGL_FORMAT",
+                            "Failed to create mFormatUsage." };
+        return false;
+    }
 
-    {
-        const auto error = gl->fGetError();
-        MOZ_ALWAYS_TRUE(!error);
+    GLenum error = gl->fGetError();
+    if (error != LOCAL_GL_NO_ERROR) {
+        const nsPrintfCString reason("GL error 0x%x occurred during OpenGL context"
+                                     " initialization, before WebGL initialization!",
+                                     error);
+        *out_failReason = { "FEATURE_FAILURE_WEBGL_GLERR_1", reason };
+        return false;
     }
 
     mDisableExtensions = gfxPrefs::WebGLDisableExtensions();
     mLoseContextOnMemoryPressure = gfxPrefs::WebGLLoseContextOnMemoryPressure();
     mCanLoseContextInForeground = gfxPrefs::WebGLCanLoseContextInForeground();
     mRestoreWhenVisible = gfxPrefs::WebGLRestoreWhenVisible();
 
     // These are the default values, see 6.2 State tables in the
@@ -598,19 +599,23 @@ WebGLContext::InitAndValidateGL(FailureR
     // Mesa can only be detected with the GL_VERSION string, of the form
     // "2.1 Mesa 7.11.0"
     const char* versionStr = (const char*)(gl->fGetString(LOCAL_GL_VERSION));
     mIsMesa = strstr(versionStr, "Mesa");
 
     // Notice that the point of calling fGetError here is not only to check for
     // errors, but also to reset the error flags so that a subsequent WebGL
     // getError call will give the correct result.
-    {
-        const auto error = gl->fGetError();
-        MOZ_ALWAYS_TRUE(!error);
+    error = gl->fGetError();
+    if (error != LOCAL_GL_NO_ERROR) {
+        const nsPrintfCString reason("GL error 0x%x occurred during WebGL context"
+                                     " initialization!",
+                                     error);
+        *out_failReason = { "FEATURE_FAILURE_WEBGL_GLERR_2", reason };
+        return false;
     }
 
     if (IsWebGL2() &&
         !InitWebGL2(out_failReason))
     {
         // Todo: Bug 898404: Only allow WebGL2 on GL>=3.0 on desktop GL.
         return false;
     }

--- a/dom/canvas/WebGLShaderValidator.cpp
+++ b/dom/canvas/WebGLShaderValidator.cpp
@@ -1,16 +1,15 @@
 /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
 /* 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 "WebGLShaderValidator.h"
 
-#include <algorithm>
 #include "gfxPrefs.h"
 #include "GLContext.h"
 #include "mozilla/gfx/Logging.h"
 #include "mozilla/Preferences.h"
 #include "MurmurHash3.h"
 #include "nsPrintfCString.h"
 #include <string>
 #include <vector>
@@ -97,32 +96,22 @@ ChooseValidatorCompileOptions(const ShBu
     return options;
 }
 
 } // namespace webgl
 
 ////////////////////////////////////////
 
 static ShShaderOutput
-ShaderOutput(gl::GLContext* const gl)
+ShaderOutput(gl::GLContext* gl)
 {
     if (gl->IsGLES()) {
         return SH_ESSL_OUTPUT;
     } else {
         uint32_t version = gl->ShadingLanguageVersion();
-
-        // Version 130 starts to require integral constant expressions for loop indices,
-        // instead of "constant-index-expression".
-        // Both version 400 and gpu_shader5 remove this restrictions.
-        // gpu_shader5 went core in 400, so we can just check for the GLFeature.
-        // If we're compiling for webglsl1, even for webgl2, we need gpu_shader5, or GLSL_COMPAT.
-        if (!gl->IsSupported(gl::GLFeature::gpu_shader5)) {
-            version = std::min<uint32_t>(version, 120);
-        }
-
         switch (version) {
         case 100: return SH_GLSL_COMPATIBILITY_OUTPUT;
         case 120: return SH_GLSL_COMPATIBILITY_OUTPUT;
         case 130: return SH_GLSL_130_OUTPUT;
         case 140: return SH_GLSL_140_OUTPUT;
         case 150: return SH_GLSL_150_CORE_OUTPUT;
         case 330: return SH_GLSL_330_CORE_OUTPUT;
         case 400: return SH_GLSL_400_CORE_OUTPUT;

--- a/dom/canvas/test/webgl-conf/generated-mochitest.ini
+++ b/dom/canvas/test/webgl-conf/generated-mochitest.ini
@@ -11112,16 +11112,17 @@ subsuite = webgl1-ext
 subsuite = webgl1-ext
 skip-if = (os == 'android')
 [generated/test_conformance__glsl__bugs__qualcomm-loop-with-continue-crash.html]
 subsuite = webgl1-ext
 [generated/test_conformance__glsl__bugs__sampler-array-struct-function-arg.html]
 subsuite = webgl1-ext
 [generated/test_conformance__glsl__bugs__sampler-array-using-loop-index.html]
 subsuite = webgl1-ext
+fail-if = (os == 'linux')
 [generated/test_conformance__glsl__bugs__sampler-struct-function-arg.html]
 subsuite = webgl1-ext
 skip-if = (os == 'linux') || (os == 'android')
 [generated/test_conformance__glsl__bugs__sequence-operator-evaluation-order.html]
 subsuite = webgl1-ext
 skip-if = (os == 'android')
 [generated/test_conformance__glsl__bugs__sketchfab-lighting-shader-crash.html]
 subsuite = webgl1-ext
@@ -11407,17 +11408,17 @@ subsuite = webgl1-ext
 [generated/test_conformance__glsl__misc__empty-declaration.html]
 subsuite = webgl1-ext
 [generated/test_conformance__glsl__misc__empty_main.vert.html]
 subsuite = webgl1-ext
 [generated/test_conformance__glsl__misc__expression-list-in-declarator-initializer.html]
 subsuite = webgl1-ext
 [generated/test_conformance__glsl__misc__fragcolor-fragdata-invariant.html]
 subsuite = webgl1-ext
-fail-if = (os == 'linux') || (os == 'mac')
+fail-if = (os == 'mac')
 [generated/test_conformance__glsl__misc__gl_position_unset.vert.html]
 subsuite = webgl1-ext
 [generated/test_conformance__glsl__misc__global-variable-init.html]
 subsuite = webgl1-ext
 [generated/test_conformance__glsl__misc__glsl-function-nodes.html]
 subsuite = webgl1-ext
 [generated/test_conformance__glsl__misc__glsl-long-variable-names.html]
 subsuite = webgl1-ext
@@ -11587,17 +11588,16 @@ subsuite = webgl1-ext
 [generated/test_conformance__glsl__misc__shader-with-while-loop.html]
 subsuite = webgl1-ext
 [generated/test_conformance__glsl__misc__shader-without-precision.frag.html]
 subsuite = webgl1-ext
 [generated/test_conformance__glsl__misc__shaders-with-constant-expression-loop-conditions.html]
 subsuite = webgl1-ext
 [generated/test_conformance__glsl__misc__shaders-with-invariance.html]
 subsuite = webgl1-ext
-fail-if = (os == 'linux')
 [generated/test_conformance__glsl__misc__shaders-with-mis-matching-uniforms.html]
 subsuite = webgl1-ext
 [generated/test_conformance__glsl__misc__shaders-with-mis-matching-varyings.html]
 subsuite = webgl1-ext
 [generated/test_conformance__glsl__misc__shaders-with-missing-varyings.html]
 subsuite = webgl1-ext
 [generated/test_conformance__glsl__misc__shaders-with-name-conflicts.html]
 subsuite = webgl1-ext

--- a/dom/canvas/test/webgl-conf/mochitest-errata.ini
+++ b/dom/canvas/test/webgl-conf/mochitest-errata.ini
@@ -188,17 +188,19 @@ skip-if = (os == 'linux') || (os == 'mac
 [generated/test_conformance__glsl__constructors__glsl-construct-ivec4.html]
 # Assume crashes like ivec3
 skip-if = (os == 'linux') || (os == 'mac')
 
 [generated/test_conformance__glsl__constructors__glsl-construct-mat2.html]
 # Crashes on Linux ASAN
 skip-if = ((os == 'linux') && asan)
 
-[generated/test_conformance__glsl__misc__shaders-with-invariance.html]
+[generated/test_conformance__glsl__bugs__sampler-array-using-loop-index.html]
+# Testfail on Linux after removing SH_UNROLL_FOR_LOOP_WITH_SAMPLER_ARRAY_INDEX.
+# Only happen on tryserver
 fail-if = (os == 'linux')
 
 [generated/test_conformance__misc__type-conversion-test.html]
 fail-if = (os == 'linux')
 # Resets device on Android 2.3.
 # Crashes on desktop Linux.
 skip-if = (os == 'android') || (os == 'linux')
 
@@ -353,17 +355,17 @@ fail-if = (os == 'mac') || (verify && de
 skip-if = (os == 'win')
 [generated/test_2_conformance__rendering__rendering-stencil-large-viewport.html]
 # same as webgl1 test
 fail-if = (os == 'mac')
 skip-if = (os == 'win')
 
 [generated/test_conformance__glsl__misc__fragcolor-fragdata-invariant.html]
 # [unexpected fragment shader compile status] (expected: true) Declaring both gl_FragColor and gl_FragData invariant should succeed.
-fail-if = (os == 'linux') || (os == 'mac')
+fail-if = (os == 'mac')
 
 ########################################################################
 # "tst-linux{32,64}-spot-NNN" Slaves:
 #   Android 2.3 and Linux.
 # Android: os == 'android'. (Not enough info to separate out 2.3)
 # Linux: os == 'linux'.
 [generated/test_conformance__glsl__bugs__temp-expressions-should-not-crash.html]
 # Coincidentally enough, crashes on Linux and Android 4.0.

--- a/dom/locales/en-US/chrome/dom/dom.properties
+++ b/dom/locales/en-US/chrome/dom/dom.properties
@@ -353,8 +353,10 @@ MixedDisplayObjectSubrequestWarning=Load
 MotionEventWarning=Use of the motion sensor is deprecated.
 OrientationEventWarning=Use of the orientation sensor is deprecated.
 ProximityEventWarning=Use of the proximity sensor is deprecated.
 AmbientLightEventWarning=Use of the ambient light sensor is deprecated.
 # LOCALIZATION NOTE: Do not translate "storage", "indexedDB.open" and "navigator.storage.persist()".
 IDBOpenDBOptions_StorageTypeWarning=The ‘storage’ attribute in options passed to indexedDB.open is deprecated and will soon be removed. To get persistent storage, please use navigator.storage.persist() instead.
 DOMQuadBoundsAttrWarning=DOMQuad.bounds is deprecated in favor of DOMQuad.getBounds()
 UnsupportedEntryTypesIgnored=Ignoring unsupported entryTypes: %S.
+# LOCALIZATION NOTE (CreateImageBitmapCanvasRenderingContext2DWarning): Do not translate CanvasRenderingContext2D and createImageBitmap.
+CreateImageBitmapCanvasRenderingContext2DWarning=Use of CanvasRenderingContext2D in createImageBitmap is deprecated.

--- a/dom/performance/Performance.cpp
+++ b/dom/performance/Performance.cpp
@@ -104,17 +104,17 @@ Performance::Now()
   const double maxResolutionMs = 0.020;
   DOMHighResTimeStamp minimallyClamped = floor(rawTime / maxResolutionMs) * maxResolutionMs;
   return nsRFPService::ReduceTimePrecisionAsMSecs(minimallyClamped, GetRandomTimelineSeed());
 }
 
 DOMHighResTimeStamp
 Performance::NowUnclamped() const
 {
-  TimeDuration duration = TimeStamp::Now() - CreationTimeStamp();
+  TimeDuration duration = TimeStamp::NowUnfuzzed() - CreationTimeStamp();
   return duration.ToMilliseconds();
 }
 
 DOMHighResTimeStamp
 Performance::TimeOrigin()
 {
   if (!mPerformanceService) {
     mPerformanceService = PerformanceService::GetOrCreate();

--- a/gfx/gl/GLContext.cpp
+++ b/gfx/gl/GLContext.cpp
@@ -92,17 +92,16 @@ static const char* const sExtensionNames
     "GL_ARB_compatibility",
     "GL_ARB_copy_buffer",
     "GL_ARB_depth_texture",
     "GL_ARB_draw_buffers",
     "GL_ARB_draw_instanced",
     "GL_ARB_framebuffer_object",
     "GL_ARB_framebuffer_sRGB",
     "GL_ARB_geometry_shader4",
-    "GL_ARB_gpu_shader5",
     "GL_ARB_half_float_pixel",
     "GL_ARB_instanced_arrays",
     "GL_ARB_internalformat_query",
     "GL_ARB_invalidate_subdata",
     "GL_ARB_map_buffer_range",
     "GL_ARB_occlusion_query2",
     "GL_ARB_pixel_buffer_object",
     "GL_ARB_robust_buffer_access_behavior",
@@ -135,17 +134,16 @@ static const char* const sExtensionNames
     "GL_EXT_draw_instanced",
     "GL_EXT_draw_range_elements",
     "GL_EXT_frag_depth",
     "GL_EXT_framebuffer_blit",
     "GL_EXT_framebuffer_multisample",
     "GL_EXT_framebuffer_object",
     "GL_EXT_framebuffer_sRGB",
     "GL_EXT_gpu_shader4",
-    "GL_EXT_gpu_shader5",
     "GL_EXT_multisampled_render_to_texture",
     "GL_EXT_occlusion_query_boolean",
     "GL_EXT_packed_depth_stencil",
     "GL_EXT_read_format_bgra",
     "GL_EXT_robustness",
     "GL_EXT_sRGB",
     "GL_EXT_sRGB_write_control",
     "GL_EXT_shader_texture_lod",
@@ -169,17 +167,16 @@ static const char* const sExtensionNames
     "GL_KHR_robust_buffer_access_behavior",
     "GL_KHR_robustness",
     "GL_KHR_texture_compression_astc_hdr",
     "GL_KHR_texture_compression_astc_ldr",
     "GL_NV_draw_instanced",
     "GL_NV_fence",
     "GL_NV_framebuffer_blit",
     "GL_NV_geometry_program4",
-    "GL_NV_gpu_shader5",
     "GL_NV_half_float",
     "GL_NV_instanced_arrays",
     "GL_NV_primitive_restart",
     "GL_NV_texture_barrier",
     "GL_NV_transform_feedback",
     "GL_NV_transform_feedback2",
     "GL_OES_EGL_image",
     "GL_OES_EGL_image_external",
@@ -376,20 +373,16 @@ GLContext::LoadFeatureSymbols(const char
         return false;
     }
     return true;
 };
 
 bool
 GLContext::InitWithPrefixImpl(const char* prefix, bool trygl)
 {
-    // see bug 929506 comment 29. wglGetProcAddress requires a current context.
-    if (!MakeCurrent(true))
-        return false;
-
     mWorkAroundDriverBugs = gfxPrefs::WorkAroundDriverBugs();
 
     const SymLoadStruct coreSymbols[] = {
         { (PRFuncPtr*) &mSymbols.fActiveTexture, { "ActiveTexture", "ActiveTextureARB", nullptr } },
         { (PRFuncPtr*) &mSymbols.fAttachShader, { "AttachShader", "AttachShaderARB", nullptr } },
         { (PRFuncPtr*) &mSymbols.fBindAttribLocation, { "BindAttribLocation", "BindAttribLocationARB", nullptr } },
         { (PRFuncPtr*) &mSymbols.fBindBuffer, { "BindBuffer", "BindBufferARB", nullptr } },
         { (PRFuncPtr*) &mSymbols.fBindTexture, { "BindTexture", "BindTextureARB", nullptr } },
@@ -516,16 +509,20 @@ GLContext::InitWithPrefixImpl(const char
         END_SYMBOLS
     };
 
     if (!LoadGLSymbols(this, prefix, trygl, coreSymbols, "GL"))
         return false;
 
     ////////////////
 
+    if (!MakeCurrent()) {
+        return false;
+    }
+
     const std::string versionStr = (const char*)fGetString(LOCAL_GL_VERSION);
     if (versionStr.find("OpenGL ES") == 0) {
         mProfile = ContextProfile::OpenGLES;
     }
 
     uint32_t majorVer, minorVer;
     if (!ParseVersion(versionStr, &majorVer, &minorVer)) {
         MOZ_ASSERT(false, "Failed to parse GL_VERSION");
@@ -2049,19 +2046,21 @@ GLContext::MarkDestroyed()
         return;
 
     // Null these before they're naturally nulled after dtor, as we want GLContext to
     // still be alive in *their* dtors.
     mScreen = nullptr;
     mBlitHelper = nullptr;
     mReadTexImageHelper = nullptr;
 
-    mIsDestroyed = true;
+    if (!MakeCurrent()) {
+        NS_WARNING("MakeCurrent() failed during MarkDestroyed! Skipping GL object teardown.");
+    }
+
     mSymbols = {};
-    (void)MakeCurrent(true); // Clear current context.
 }
 
 #ifdef MOZ_GL_DEBUG
 /* static */ void
 GLContext::AssertNotPassingStackBufferToTheGL(const void* ptr)
 {
   int somethingOnTheStack;
   const void* someStackPtr = &somethingOnTheStack;
@@ -2937,36 +2936,36 @@ GetBytesPerTexel(GLenum format, GLenum t
         return 2;
     }
 
     gfxCriticalError() << "Unknown texture type " << type << " or format " << format;
     return 0;
 }
 
 bool
-GLContext::MakeCurrent(const bool aForce) const
+GLContext::MakeCurrent(bool aForce) const
 {
-    if (MOZ_LIKELY( !aForce & !IsDestroyed() )) {
-        bool isCurrent = false;
+    if (MOZ_UNLIKELY( IsDestroyed() ))
+        return false;
+
+    if (MOZ_LIKELY( !aForce )) {
+        bool isCurrent;
         if (mUseTLSIsCurrent) {
             isCurrent = (sCurrentContext.get() == reinterpret_cast<uintptr_t>(this));
-        }
-        if (MOZ_UNLIKELY( !isCurrent )) {
+        } else {
             isCurrent = IsCurrentImpl();
         }
         if (MOZ_LIKELY( isCurrent )) {
             MOZ_ASSERT(IsCurrentImpl());
             return true;
         }
     }
 
-    if (MOZ_UNLIKELY( !MakeCurrentImpl() )) {
-        ClearGetCurrentContextTLS();
+    if (!MakeCurrentImpl())
         return false;
-    }
 
     sCurrentContext.set(reinterpret_cast<uintptr_t>(this));
     return true;
 }
 
 void
 GLContext::ResetSyncCallCount(const char* resetReason) const
 {

--- a/gfx/gl/GLContext.h
+++ b/gfx/gl/GLContext.h
@@ -98,17 +98,16 @@ enum class GLFeature {
     framebuffer_multisample,
     framebuffer_object,
     framebuffer_object_EXT_OES,
     get_integer_indexed,
     get_integer64_indexed,
     get_query_object_i64v,
     get_query_object_iv,
     gpu_shader4,
-    gpu_shader5,
     instanced_arrays,
     instanced_non_arrays,
     internalformat_query,
     invalidate_framebuffer,
     map_buffer_range,
     occlusion_query,
     occlusion_query_boolean,
     occlusion_query2,
@@ -196,20 +195,16 @@ class GLContext
     : public GLLibraryLoader
     , public GenericAtomicRefCounted
     , public SupportsWeakPtr<GLContext>
 {
 public:
     MOZ_DECLARE_WEAKREFERENCE_TYPENAME(GLContext)
     static MOZ_THREAD_LOCAL(uintptr_t) sCurrentContext;
 
-    static void ClearGetCurrentContextTLS() {
-        sCurrentContext.set(0);
-    }
-
     bool mImplicitMakeCurrent = false;
     bool mUseTLSIsCurrent;
 
     class TlsScope final {
         const WeakPtr<GLContext> mGL;
         const bool mWasTlsOk;
     public:
         explicit TlsScope(GLContext* const gl)
@@ -341,17 +336,16 @@ public:
      */
     virtual GLuint GetDefaultFramebuffer() {
         return 0;
     }
 
 protected:
     bool mIsOffscreen;
     mutable bool mContextLost = false;
-    bool mIsDestroyed = false;
 
     /**
      * mVersion store the OpenGL's version, multiplied by 100. For example, if
      * the context is an OpenGL 2.1 context, mVersion value will be 210.
      */
     uint32_t mVersion = 0;
     ContextProfile mProfile = ContextProfile::Unknown;
 
@@ -399,17 +393,16 @@ public:
         ARB_compatibility,
         ARB_copy_buffer,
         ARB_depth_texture,
         ARB_draw_buffers,
         ARB_draw_instanced,
         ARB_framebuffer_object,
         ARB_framebuffer_sRGB,
         ARB_geometry_shader4,
-        ARB_gpu_shader5,
         ARB_half_float_pixel,
         ARB_instanced_arrays,
         ARB_internalformat_query,
         ARB_invalidate_subdata,
         ARB_map_buffer_range,
         ARB_occlusion_query2,
         ARB_pixel_buffer_object,
         ARB_robust_buffer_access_behavior,
@@ -442,17 +435,16 @@ public:
         EXT_draw_instanced,
         EXT_draw_range_elements,
         EXT_frag_depth,
         EXT_framebuffer_blit,
         EXT_framebuffer_multisample,
         EXT_framebuffer_object,
         EXT_framebuffer_sRGB,
         EXT_gpu_shader4,
-        EXT_gpu_shader5,
         EXT_multisampled_render_to_texture,
         EXT_occlusion_query_boolean,
         EXT_packed_depth_stencil,
         EXT_read_format_bgra,
         EXT_robustness,
         EXT_sRGB,
         EXT_sRGB_write_control,
         EXT_shader_texture_lod,
@@ -476,17 +468,16 @@ public:
         KHR_robust_buffer_access_behavior,
         KHR_robustness,
         KHR_texture_compression_astc_hdr,
         KHR_texture_compression_astc_ldr,
         NV_draw_instanced,
         NV_fence,
         NV_framebuffer_blit,
         NV_geometry_program4,
-        NV_gpu_shader5,
         NV_half_float,
         NV_instanced_arrays,
         NV_primitive_restart,
         NV_texture_barrier,
         NV_transform_feedback,
         NV_transform_feedback2,
         OES_EGL_image,
         OES_EGL_image_external,
@@ -3378,17 +3369,18 @@ protected:
 public:
     virtual bool Init() = 0;
 
     virtual bool SetupLookupFunction() = 0;
 
     virtual void ReleaseSurface() {}
 
     bool IsDestroyed() const {
-        return mIsDestroyed;
+        // MarkDestroyed will mark all these as null.
+        return mSymbols.fUseProgram == nullptr;
     }
 
     GLContext* GetSharedContext() { return mSharedContext; }
 
     /**
      * Returns true if the thread on which this context was created is the currently
      * executing thread.
      */

--- a/gfx/gl/GLContextCGL.h
+++ b/gfx/gl/GLContextCGL.h
@@ -19,17 +19,17 @@ typedef void NSOpenGLContext;
 
 namespace mozilla {
 namespace gl {
 
 class GLContextCGL : public GLContext
 {
     friend class GLContextProviderCGL;
 
-    NSOpenGLContext* const mContext;
+    NSOpenGLContext* mContext;
 
 public:
     MOZ_DECLARE_REFCOUNTED_VIRTUAL_TYPENAME(GLContextCGL, override)
     GLContextCGL(CreateContextFlags flags, const SurfaceCaps& caps,
                  NSOpenGLContext* context, bool isOffscreen);
 
     ~GLContextCGL();
 

--- a/gfx/gl/GLContextFeatures.cpp
+++ b/gfx/gl/GLContextFeatures.cpp
@@ -317,28 +317,16 @@ static const FeatureInfo sFeatureInfoArr
         GLESVersion::ES3,
         GLContext::Extension_None,
         {
             GLContext::EXT_gpu_shader4,
             GLContext::Extensions_End
         }
     },
     {
-        "gpu_shader5",
-        GLVersion::GL4,
-        GLESVersion::NONE,
-        GLContext::Extension_None,
-        {
-            GLContext::ARB_gpu_shader5,
-            GLContext::EXT_gpu_shader5,
-            GLContext::NV_gpu_shader5,
-            GLContext::Extensions_End
-        }
-    },
-    {
         "instanced_arrays",
         GLVersion::GL3_3,
         GLESVersion::ES3,
         GLContext::Extension_None,
         {
             GLContext::ARB_instanced_arrays,
             GLContext::NV_instanced_arrays,
             GLContext::ANGLE_instanced_arrays,

--- a/gfx/gl/GLContextGLX.h
+++ b/gfx/gl/GLContextGLX.h
@@ -82,17 +82,16 @@ private:
                  GLXContext aContext,
                  bool aDeleteDrawable,
                  bool aDoubleBuffered,
                  gfxXlibSurface* aPixmap);
 
     GLXContext mContext;
     Display* mDisplay;
     GLXDrawable mDrawable;
-    Maybe<GLXDrawable> mOverrideDrawable;
     bool mDeleteDrawable;
     bool mDoubleBuffered;
 
     GLXLibrary* mGLX;
 
     RefPtr<gfxXlibSurface> mPixmap;
     bool mOwnsContext = true;
 };

--- a/gfx/gl/GLContextProviderCGL.mm
+++ b/gfx/gl/GLContextProviderCGL.mm
@@ -71,39 +71,46 @@ GLContextCGL::GLContextCGL(CreateContext
     : GLContext(flags, caps, nullptr, isOffscreen)
     , mContext(context)
 {
 }
 
 GLContextCGL::~GLContextCGL()
 {
     MarkDestroyed();
-    [mContext release];
+
+    if (mContext) {
+        if ([NSOpenGLContext currentContext] == mContext) {
+            // Clear the current context before releasing. If we don't do
+            // this, the next time we call [NSOpenGLContext currentContext],
+            // "invalid context" will be printed to the console.
+            [NSOpenGLContext clearCurrentContext];
+        }
+        [mContext release];
+    }
 }
 
 bool
 GLContextCGL::Init()
 {
-    return InitWithPrefix("gl", true);
+    if (!InitWithPrefix("gl", true))
+        return false;
+
+    return true;
 }
 
 CGLContextObj
 GLContextCGL::GetCGLContext() const
 {
     return static_cast<CGLContextObj>([mContext CGLContextObj]);
 }
 
 bool
 GLContextCGL::MakeCurrentImpl() const
 {
-    if (IsDestroyed()) {
-        [NSOpenGLContext clearCurrentContext];
-        return false;
-    }
-
     if (mContext) {
         [mContext makeCurrentContext];
         MOZ_ASSERT(IsCurrentImpl());
         // Use non-blocking swap in "ASAP mode".
         // ASAP mode means that rendering is iterated as fast as possible.
         // ASAP mode is entered when layout.frame_rate=0 (requires restart).
         // If swapInt is 1, then glSwapBuffers will block and wait for a vblank signal.
         // When we're iterating as fast as possible, however, we want a non-blocking

--- a/gfx/gl/GLContextProviderEAGL.mm
+++ b/gfx/gl/GLContextProviderEAGL.mm
@@ -27,36 +27,45 @@ GLContextEAGL::GLContextEAGL(CreateConte
                              bool isOffscreen)
     : GLContext(flags, caps, sharedContext, isOffscreen)
     , mContext(context)
 {
 }
 
 GLContextEAGL::~GLContextEAGL()
 {
-    if (MakeCurrent()) {
-        if (mBackbufferFB) {
-            fDeleteFramebuffers(1, &mBackbufferFB);
-        }
+    MakeCurrent();
 
-        if (mBackbufferRB) {
-            fDeleteRenderbuffers(1, &mBackbufferRB);
-        }
+    if (mBackbufferFB) {
+        fDeleteFramebuffers(1, &mBackbufferFB);
+    }
+
+    if (mBackbufferRB) {
+        fDeleteRenderbuffers(1, &mBackbufferRB);
     }
 
-    mLayer = nil;
+    MarkDestroyed();
 
-    MarkDestroyed();
-    [mContext release];
+    if (mLayer) {
+      mLayer = nil;
+    }
+
+    if (mContext) {
+      [EAGLContext setCurrentContext:nil];
+      [mContext release];
+    }
 }
 
 bool
 GLContextEAGL::Init()
 {
-    return InitWithPrefix("gl", true);
+    if (!InitWithPrefix("gl", true))
+        return false;
+
+    return true;
 }
 
 bool
 GLContextEAGL::AttachToWindow(nsIWidget* aWidget)
 {
     // This should only be called once
     MOZ_ASSERT(!mBackbufferFB && !mBackbufferRB);
 
@@ -98,21 +107,22 @@ GLContextEAGL::RecreateRB()
                              LOCAL_GL_RENDERBUFFER, mBackbufferRB);
 
     return LOCAL_GL_FRAMEBUFFER_COMPLETE == fCheckFramebufferStatus(LOCAL_GL_FRAMEBUFFER);
 }
 
 bool
 GLContextEAGL::MakeCurrentImpl() const
 {
-    if (IsDestroyed()) {
-        [EAGLContext setCurrentContext:nil];
-        return false;
+    if (mContext) {
+        if(![EAGLContext setCurrentContext:mContext]) {
+            return false;
+        }
     }
-    return [EAGLContext setCurrentContext:mContext];
+    return true;
 }
 
 bool
 GLContextEAGL::IsCurrentImpl() const
 {
     return [EAGLContext currentContext] == mContext;
 }
 

--- a/gfx/gl/GLContextProviderEGL.cpp
+++ b/gfx/gl/GLContextProviderEGL.cpp
@@ -153,28 +153,29 @@ is_power_of_two(int v)
 
     if (v == 0)
         return true;
 
     return (v & (v-1)) == 0;
 }
 
 static void
-DestroySurface(const EGLSurface surf)
-{
-    if (!surf)
-        return;
+DestroySurface(EGLSurface oldSurface) {
+    auto* egl = gl::GLLibraryEGL::Get();
 
-    const auto& egl = gl::GLLibraryEGL::Get();
-
-    // TODO: This breaks TLS MakeCurrent caching.
-    MOZ_ALWAYS_TRUE( egl->fDestroySurface(EGL_DISPLAY(), surf) );
+    if (oldSurface != EGL_NO_SURFACE) {
+        // TODO: This breaks TLS MakeCurrent caching.
+        egl->fMakeCurrent(EGL_DISPLAY(),
+                          EGL_NO_SURFACE, EGL_NO_SURFACE,
+                          EGL_NO_CONTEXT);
+        egl->fDestroySurface(EGL_DISPLAY(), oldSurface);
 #if defined(MOZ_WAYLAND)
-    DeleteWaylandGLSurface(surf);
+        DeleteWaylandGLSurface(oldSurface);
 #endif
+    }
 }
 
 static EGLSurface
 CreateFallbackSurface(const EGLConfig& config)
 {
     nsCString discardFailureId;
     if (!GLLibraryEGL::EnsureInitialized(false, &discardFailureId)) {
         gfxCriticalNote << "Failed to load EGL library 3!";
@@ -278,17 +279,17 @@ GLContextEGLFactory::Create(EGLNativeWin
     if (aWebRender) {
         flags |= CreateContextFlags::PREFER_ES3;
     }
     SurfaceCaps caps = SurfaceCaps::Any();
     RefPtr<GLContextEGL> gl = GLContextEGL::CreateGLContext(flags, caps, false, config,
                                                             surface, &discardFailureId);
     if (!gl) {
         gfxCriticalNote << "Failed to create EGLContext!";
-        DestroySurface(surface);
+        mozilla::gl::DestroySurface(surface);
         return nullptr;
     }
 
     gl->MakeCurrent();
     gl->SetIsDoubleBuffered(doubleBuffered);
     if (aWebRender && egl->IsANGLE()) {
         MOZ_ASSERT(doubleBuffered);
         egl->fSwapInterval(EGL_DISPLAY(), 0);
@@ -320,19 +321,19 @@ GLContextEGL::~GLContextEGL()
         return;
     }
 
 #ifdef DEBUG
     printf_stderr("Destroying context %p surface %p on display %p\n", mContext, mSurface, EGL_DISPLAY());
 #endif
 
     mEgl->fDestroyContext(EGL_DISPLAY(), mContext);
-    DestroySurface(mSurface);
-    MOZ_ASSERT(!mFallbackSurface || mFallbackSurface != mSurface);
-    DestroySurface(mFallbackSurface);
+
+    mozilla::gl::DestroySurface(mSurface);
+    mozilla::gl::DestroySurface(mFallbackSurface);
 }
 
 bool
 GLContextEGL::Init()
 {
 #if defined(ANDROID)
     // We can't use LoadApitraceLibrary here because the GLContext
     // expects its own handle to the GL library
@@ -345,17 +346,23 @@ GLContextEGL::Init()
                 return false;
             }
 #endif
         }
 
     SetupLookupFunction();
     if (!InitWithPrefix("gl", true))
         return false;
-    MOZ_ASSERT(IsCurrent());
+
+    bool current = MakeCurrent();
+    if (!current) {
+        gfx::LogFailure(NS_LITERAL_CSTRING(
+            "Couldn't get device attachments for device."));
+        return false;
+    }
 
     static_assert(sizeof(GLint) >= sizeof(int32_t), "GLint is smaller than int32_t");
     mMaxTextureImageSize = INT32_MAX;
 
     mShareWithEGLImage = mEgl->HasKHRImageBase() &&
                          mEgl->HasKHRImageTexture2D() &&
                          IsExtensionSupported(OES_EGL_image);
 
@@ -396,45 +403,36 @@ GLContextEGL::ReleaseTexImage()
     if (success == LOCAL_EGL_FALSE)
         return false;
 
     mBound = false;
     return true;
 }
 
 void
-GLContextEGL::SetEGLSurfaceOverride(const EGLSurface surf)
-{
-    MOZ_ASSERT(!surf || surf != mSurface);
-
+GLContextEGL::SetEGLSurfaceOverride(EGLSurface surf) {
     if (Screen()) {
         /* Blit `draw` to `read` if we need to, before we potentially juggle
           * `read` around. If we don't, we might attach a different `read`,
           * and *then* hit AssureBlitted, which will blit a dirty `draw` onto
           * the wrong `read`!
           */
         Screen()->AssureBlitted();
     }
 
     mSurfaceOverride = surf;
-    MOZ_ALWAYS_TRUE( MakeCurrent(true) );
+    DebugOnly<bool> ok = MakeCurrent(true);
+    MOZ_ASSERT(ok);
 }
 
 bool
 GLContextEGL::MakeCurrentImpl() const
 {
-    if (IsDestroyed()) {
-        MOZ_ALWAYS_TRUE( mEgl->fMakeCurrent(EGL_DISPLAY(), nullptr, nullptr, nullptr) );
-        return false;
-    }
-
-    auto surface = mSurface;
-    if (mSurfaceOverride) {
-        surface = mSurfaceOverride;
-    }
+    EGLSurface surface = (mSurfaceOverride != EGL_NO_SURFACE) ? mSurfaceOverride
+                                                              : mSurface;
     if (!surface) {
         surface = mFallbackSurface;
     }
 
     const bool succeeded = mEgl->fMakeCurrent(EGL_DISPLAY(), surface, surface,
                                               mContext);
     if (!succeeded) {
         const auto eglError = mEgl->fGetError();
@@ -454,18 +452,17 @@ GLContextEGL::MakeCurrentImpl() const
 
 bool
 GLContextEGL::IsCurrentImpl() const
 {
     return mEgl->fGetCurrentContext() == mContext;
 }
 
 bool
-GLContextEGL::RenewSurface(CompositorWidget* const aWidget)
-{
+GLContextEGL::RenewSurface(CompositorWidget* aWidget) {
     if (!mOwnsContext) {
         return false;
     }
     // unconditionally release the surface and create a new one. Don't try to optimize this away.
     // If we get here, then by definition we know that we want to get a new surface.
     ReleaseSurface();
     MOZ_ASSERT(aWidget);
 
@@ -477,23 +474,24 @@ GLContextEGL::RenewSurface(CompositorWid
             return false;
         }
     }
 
     return MakeCurrent(true);
 }
 
 void
-GLContextEGL::ReleaseSurface()
-{
-    if (!mOwnsContext)
-        return;
-
-    DestroySurface(mSurface);
-    mSurface = nullptr;
+GLContextEGL::ReleaseSurface() {
+    if (mOwnsContext) {
+        mozilla::gl::DestroySurface(mSurface);
+    }
+    if (mSurface == mSurfaceOverride) {
+        mSurfaceOverride = EGL_NO_SURFACE;
+    }
+    mSurface = EGL_NO_SURFACE;
 }
 
 bool
 GLContextEGL::SetupLookupFunction()
 {
     mLookupFunc = mEgl->GetLookupFunction();
     return true;
 }

--- a/gfx/gl/GLContextProviderGLX.cpp
+++ b/gfx/gl/GLContextProviderGLX.cpp
@@ -582,22 +582,30 @@ GLContextGLX::~GLContextGLX()
 {
     MarkDestroyed();
 
     // Wrapped context should not destroy glxContext/Surface
     if (!mOwnsContext) {
         return;
     }
 
+    // see bug 659842 comment 76
+#ifdef DEBUG
+    bool success =
+#endif
+    mGLX->fMakeCurrent(mDisplay, X11None, nullptr);
+    MOZ_ASSERT(success,
+               "glXMakeCurrent failed to release GL context before we call "
+               "glXDestroyContext!");
+
     mGLX->fDestroyContext(mDisplay, mContext);
 
     if (mDeleteDrawable) {
         mGLX->fDestroyPixmap(mDisplay, mDrawable);
     }
-    MOZ_ASSERT(!mOverrideDrawable);
 }
 
 
 bool
 GLContextGLX::Init()
 {
     SetupLookupFunction();
     if (!InitWithPrefix("gl", true)) {
@@ -616,26 +624,17 @@ bool
 GLContextGLX::MakeCurrentImpl() const
 {
     if (mGLX->IsMesa()) {
         // Read into the event queue to ensure that Mesa receives a
         // DRI2InvalidateBuffers event before drawing. See bug 1280653.
         Unused << XPending(mDisplay);
     }
 
-    if (IsDestroyed()) {
-        MOZ_ALWAYS_TRUE( mGLX->fMakeCurrent(mDisplay, X11None, nullptr) );
-        return false; // Did not MakeCurrent mContext, but that's what we wanted!
-    }
-
-    auto drawable = mDrawable;
-    if (mOverrideDrawable) {
-        drawable = mOverrideDrawable.ref();
-    }
-    const bool succeeded = mGLX->fMakeCurrent(mDisplay, drawable, mContext);
+    const bool succeeded = mGLX->fMakeCurrent(mDisplay, mDrawable, mContext);
     NS_ASSERTION(succeeded, "Failed to make GL context current!");
 
     if (!IsOffscreen() && mGLX->SupportsSwapControl()) {
         // Many GLX implementations default to blocking until the next
         // VBlank when calling glXSwapBuffers. We want to run unthrottled
         // in ASAP mode. See bug 1280744.
         const bool isASAP = (gfxPrefs::LayoutFrameRate() == 0);
         mGLX->fSwapInterval(mDisplay, mDrawable, isASAP ? 0 : 1);
@@ -690,28 +689,26 @@ GLContextGLX::GetWSIInfo(nsCString* cons
 
     out->AppendLiteral("\nExtensions: ");
     out->Append(sGLXLibrary.fQueryExtensionsString(display, screen));
 }
 
 bool
 GLContextGLX::OverrideDrawable(GLXDrawable drawable)
 {
-    if (Screen()) {
+    if (Screen())
         Screen()->AssureBlitted();
-    }
-    mOverrideDrawable = Some(drawable);
-    return MakeCurrent(true);
+    Bool result = mGLX->fMakeCurrent(mDisplay, drawable, mContext);
+    return result;
 }
 
 bool
 GLContextGLX::RestoreDrawable()
 {
-    mOverrideDrawable = Nothing();
-    return MakeCurrent(true);
+    return mGLX->fMakeCurrent(mDisplay, mDrawable, mContext);
 }
 
 GLContextGLX::GLContextGLX(
                   CreateContextFlags flags,
                   const SurfaceCaps& caps,
                   bool isOffscreen,
                   Display* aDisplay,
                   GLXDrawable aDrawable,

--- a/gfx/gl/GLContextProviderWGL.cpp
+++ b/gfx/gl/GLContextProviderWGL.cpp
@@ -158,16 +158,17 @@ WGLLibrary::EnsureInitialized()
 
     // create rendering context
     mDummyGlrc = mSymbols.fCreateContext(mRootDc);
     if (!mDummyGlrc)
         return false;
 
     const auto curCtx = mSymbols.fGetCurrentContext();
     const auto curDC = mSymbols.fGetCurrentDC();
+
     if (!mSymbols.fMakeCurrent(mRootDc, mDummyGlrc)) {
         NS_WARNING("wglMakeCurrent failed");
         return false;
     }
     const auto resetContext = MakeScopeExit([&]() {
         mSymbols.fMakeCurrent(curDC, curCtx);
     });
 
@@ -293,16 +294,17 @@ GLContextWGL::GLContextWGL(CreateContext
       mPBuffer(aPbuffer),
       mPixelFormat(aPixelFormat)
 {
 }
 
 GLContextWGL::~GLContextWGL()
 {
     MarkDestroyed();
+
     (void)sWGLLib.mSymbols.fDeleteContext(mContext);
 
     if (mPBuffer) {
         (void)sWGLLib.mSymbols.fReleasePbufferDC(mPBuffer, mDC);
         (void)sWGLLib.mSymbols.fDestroyPbuffer(mPBuffer);
     }
     if (mWnd) {
         (void)ReleaseDC(mWnd, mDC);
@@ -311,28 +313,30 @@ GLContextWGL::~GLContextWGL()
 }
 
 bool
 GLContextWGL::Init()
 {
     if (!mDC || !mContext)
         return false;
 
+    // see bug 929506 comment 29. wglGetProcAddress requires a current context.
+    if (!sWGLLib.mSymbols.fMakeCurrent(mDC, mContext))
+        return false;
+
     SetupLookupFunction();
-    return InitWithPrefix("gl", true);
+    if (!InitWithPrefix("gl", true))
+        return false;
+
+    return true;
 }
 
 bool
 GLContextWGL::MakeCurrentImpl() const
 {
-    if (IsDestroyed()) {
-        MOZ_ALWAYS_TRUE( sWGLLib.mSymbols.fMakeCurrent(0, 0) );
-        return false;
-    }
-
     const bool succeeded = sWGLLib.mSymbols.fMakeCurrent(mDC, mContext);
     NS_ASSERTION(succeeded, "Failed to make GL context current!");
     return succeeded;
 }
 
 bool
 GLContextWGL::IsCurrentImpl() const
 {

--- a/ipc/glue/IPCMessageUtils.h
+++ b/ipc/glue/IPCMessageUtils.h
@@ -822,25 +822,53 @@ struct ParamTraits<mozilla::TimeStamp>
 template<>
 struct ParamTraits<mozilla::TimeStampValue>
 {
   typedef mozilla::TimeStampValue paramType;
   static void Write(Message* aMsg, const paramType& aParam)
   {
     WriteParam(aMsg, aParam.mGTC);
     WriteParam(aMsg, aParam.mQPC);
+    WriteParam(aMsg, aParam.mUsedCanonicalNow);
+    WriteParam(aMsg, aParam.mIsNull);
     WriteParam(aMsg, aParam.mHasQPC);
-    WriteParam(aMsg, aParam.mIsNull);
   }
   static bool Read(const Message* aMsg, PickleIterator* aIter, paramType* aResult)
   {
     return (ReadParam(aMsg, aIter, &aResult->mGTC) &&
             ReadParam(aMsg, aIter, &aResult->mQPC) &&
-            ReadParam(aMsg, aIter, &aResult->mHasQPC) &&
-            ReadParam(aMsg, aIter, &aResult->mIsNull));
+            ReadParam(aMsg, aIter, &aResult->mUsedCanonicalNow) &&
+            ReadParam(aMsg, aIter, &aResult->mIsNull) &&
+            ReadParam(aMsg, aIter, &aResult->mHasQPC));
+  }
+};
+
+#else
+
+template<>
+struct ParamTraits<mozilla::TimeStamp63Bit>
+{
+  typedef mozilla::TimeStamp63Bit paramType;
+  static void Write(Message* aMsg, const paramType& aParam)
+  {
+    WriteParam(aMsg, aParam.mUsedCanonicalNow);
+    WriteParam(aMsg, aParam.mTimeStamp);
+  }
+  static bool Read(const Message* aMsg, PickleIterator* aIter, paramType* aResult)
+  {
+    bool success = true;
+    uint64_t result;
+
+    success &= ReadParam(aMsg, aIter, &result);
+    aResult->mUsedCanonicalNow = result & 0x01;
+
+    success &= ReadParam(aMsg, aIter, &result);
+    aResult->mTimeStamp = result & 0x7FFFFFFFFFFFFFFF;
+
+    return success;
   }
 };
 
 #endif
 
 template <>
 struct ParamTraits<mozilla::dom::ipc::StructuredCloneData>
 {

--- a/js/ffi.configure
+++ b/js/ffi.configure
@@ -28,21 +28,21 @@ add_old_configure_assignment('MOZ_SYSTEM
 # Target selection, based on ffi/configure.ac.
 @depends(target, when=building_ffi)
 def ffi_target(target):
     if target.cpu not in ('x86', 'x86_64', 'arm', 'aarch64'):
         die('Building libffi from the tree is not supported on this platform. '
             'Use --with-system-ffi instead.')
 
     if target.os == 'WINNT':
-        target_dir = 'x86'
-        if target.cpu == 'x86_64':
-            target_name = 'X86_WIN64'
-        else:
-            target_name = 'X86_WIN32'
+        target_dir, target_name = {
+            'x86_64': ('x86', 'X86_WIN64'),
+            'x86': ('x86', 'X86_WIN32'),
+            'aarch64': ('aarch64', 'ARM64_WIN64'),
+        }[target.cpu]
     elif target.os == 'OSX':
         target_dir = 'x86'
         target_name = 'X86_DARWIN'
     elif target.cpu == 'arm':
         target_dir = 'arm'
         target_name = 'ARM'
     elif target.cpu == 'aarch64':
         target_dir = 'aarch64'

--- a/js/src/builtin/intl/DateTimeFormat.js
+++ b/js/src/builtin/intl/DateTimeFormat.js
@@ -875,59 +875,42 @@ function Intl_DateTimeFormat_resolvedOpt
     }
 
     resolveICUPattern(internals.pattern, result);
 
     // Step 6.
     return result;
 }
 
-// Table mapping ICU pattern characters back to the corresponding date-time
-// components of DateTimeFormat. See
-// http://unicode.org/reports/tr35/tr35-dates.html#Date_Field_Symbol_Table
-var icuPatternCharToComponent = {
-    E: "weekday",
-    G: "era",
-    y: "year",
-    M: "month",
-    L: "month",
-    d: "day",
-    h: "hour",
-    H: "hour",
-    k: "hour",
-    K: "hour",
-    m: "minute",
-    s: "second",
-    z: "timeZoneName",
-    v: "timeZoneName",
-    V: "timeZoneName",
-};
-
+/* eslint-disable complexity */
 /**
  * Maps an ICU pattern string to a corresponding set of date-time components
  * and their values, and adds properties for these components to the result
  * object, which will be returned by the resolvedOptions method. For the
  * interpretation of ICU pattern characters, see
  * http://unicode.org/reports/tr35/tr35-dates.html#Date_Field_Symbol_Table
  */
 function resolveICUPattern(pattern, result) {
     assert(IsObject(result), "resolveICUPattern");
+
+    var hourCycle, weekday, era, year, month, day, hour, minute, second, timeZoneName;
     var i = 0;
     while (i < pattern.length) {
         var c = pattern[i++];
         if (c === "'") {
             while (i < pattern.length && pattern[i] !== "'")
                 i++;
             i++;
         } else {
             var count = 1;
             while (i < pattern.length && pattern[i] === c) {
                 i++;
                 count++;
             }
+
             var value;
             switch (c) {
             // "text" cases
             case "G":
             case "E":
             case "z":
             case "v":
             case "V":
@@ -964,31 +947,93 @@ function resolveICUPattern(pattern, resu
                 else if (count === 4)
                     value = "long";
                 else
                     value = "narrow";
                 break;
             default:
                 // skip other pattern characters and literal text
             }
-            if (hasOwn(c, icuPatternCharToComponent))
-                _DefineDataProperty(result, icuPatternCharToComponent[c], value);
+
+            // Map ICU pattern characters back to the corresponding date-time
+            // components of DateTimeFormat. See
+            // http://unicode.org/reports/tr35/tr35-dates.html#Date_Field_Symbol_Table
             switch (c) {
+            case "E":
+                weekday = value;
+                break;
+            case "G":
+                era = value;
+                break;
+            case "y":
+                year = value;
+                break;
+            case "M":
+            case "L":
+                month = value;
+                break;
+            case "d":
+                day = value;
+                break;
             case "h":
-                _DefineDataProperty(result, "hourCycle", "h12");
-                _DefineDataProperty(result, "hour12", true);
+                hourCycle = "h12";
+                hour = value;
+                break;
+            case "H":
+                hourCycle = "h23";
+                hour = value;
+                break;
+            case "k":
+                hourCycle = "h24";
+                hour = value;
                 break;
             case "K":
-                _DefineDataProperty(result, "hourCycle", "h11");
-                _DefineDataProperty(result, "hour12", true);
+                hourCycle = "h11";
+                hour = value;
+                break;
+            case "m":
+                minute = value;
                 break;
-            case "H":
-                _DefineDataProperty(result, "hourCycle", "h23");
-                _DefineDataProperty(result, "hour12", false);
+            case "s":
+                second = value;
                 break;
-            case "k":
-                _DefineDataProperty(result, "hourCycle", "h24");
-                _DefineDataProperty(result, "hour12", false);
+            case "z":
+            case "v":
+            case "V":
+                timeZoneName = value;
                 break;
             }
         }
     }
+
+    if (hourCycle) {
+        _DefineDataProperty(result, "hourCycle", hourCycle);
+        _DefineDataProperty(result, "hour12", hourCycle === "h11" || hourCycle === "h12");
+    }
+    if (weekday) {
+        _DefineDataProperty(result, "weekday", weekday);
+    }
+    if (era) {
+        _DefineDataProperty(result, "era", era);
+    }
+    if (year) {
+        _DefineDataProperty(result, "year", year);
+    }
+    if (month) {
+        _DefineDataProperty(result, "month", month);
+    }
+    if (day) {
+        _DefineDataProperty(result, "day", day);
+    }
+    if (hour) {
+        _DefineDataProperty(result, "hour", hour);
+    }
+    if (minute) {
+        _DefineDataProperty(result, "minute", minute);
+    }
+    if (second) {
+        _DefineDataProperty(result, "second", second);
+    }
+    if (timeZoneName) {
+        _DefineDataProperty(result, "timeZoneName", timeZoneName);
+    }
 }
+/* eslint-enable complexity */

--- a/js/src/builtin/intl/NumberFormat.js
+++ b/js/src/builtin/intl/NumberFormat.js
@@ -475,40 +475,42 @@ function Intl_NumberFormat_resolvedOptio
 
     var internals = getNumberFormatInternals(nf);
 
     // Steps 4-5.
     var result = {
         locale: internals.locale,
         numberingSystem: internals.numberingSystem,
         style: internals.style,
-        minimumIntegerDigits: internals.minimumIntegerDigits,
-        minimumFractionDigits: internals.minimumFractionDigits,
-        maximumFractionDigits: internals.maximumFractionDigits,
-        useGrouping: internals.useGrouping,
     };
 
     // currency and currencyDisplay are only present for currency formatters.
     assert(hasOwn("currency", internals) === (internals.style === "currency"),
            "currency is present iff style is 'currency'");
     assert(hasOwn("currencyDisplay", internals) === (internals.style === "currency"),
            "currencyDisplay is present iff style is 'currency'");
 
     if (hasOwn("currency", internals)) {
         _DefineDataProperty(result, "currency", internals.currency);
         _DefineDataProperty(result, "currencyDisplay", internals.currencyDisplay);
     }
 
+    _DefineDataProperty(result, "minimumIntegerDigits", internals.minimumIntegerDigits);
+    _DefineDataProperty(result, "minimumFractionDigits", internals.minimumFractionDigits);
+    _DefineDataProperty(result, "maximumFractionDigits", internals.maximumFractionDigits);
+
     // Min/Max significant digits are either both present or not at all.
     assert(hasOwn("minimumSignificantDigits", internals) ===
            hasOwn("maximumSignificantDigits", internals),
            "minimumSignificantDigits is present iff maximumSignificantDigits is present");
 
     if (hasOwn("minimumSignificantDigits", internals)) {
         _DefineDataProperty(result, "minimumSignificantDigits",
                             internals.minimumSignificantDigits);
         _DefineDataProperty(result, "maximumSignificantDigits",
                             internals.maximumSignificantDigits);
     }
 
+    _DefineDataProperty(result, "useGrouping", internals.useGrouping);
+
     // Step 6.
     return result;
 }

--- a/js/src/builtin/intl/PluralRules.js
+++ b/js/src/builtin/intl/PluralRules.js
@@ -221,34 +221,20 @@ function Intl_PluralRules_resolvedOption
     // Steps 2-3.
     if (!IsObject(pluralRules) || (pluralRules = GuardToPluralRules(pluralRules)) === null) {
         ThrowTypeError(JSMSG_INTL_OBJECT_NOT_INITED, "PluralRules", "resolvedOptions",
                        "PluralRules");
     }
 
     var internals = getPluralRulesInternals(pluralRules);
 
-    var internalsPluralCategories = internals.pluralCategories;
-    if (internalsPluralCategories === null) {
-        internalsPluralCategories = intl_GetPluralCategories(pluralRules);
-        internals.pluralCategories = internalsPluralCategories;
-    }
-
-    // TODO: The current spec actually requires to return the internal array
-    // object and not a copy of it.
-    // <https://github.com/tc39/proposal-intl-plural-rules/issues/28#issuecomment-341557030>
-    var pluralCategories = [];
-    for (var i = 0; i < internalsPluralCategories.length; i++)
-        _DefineDataProperty(pluralCategories, i, internalsPluralCategories[i]);
-
     // Steps 4-5.
     var result = {
         locale: internals.locale,
         type: internals.type,
-        pluralCategories,
         minimumIntegerDigits: internals.minimumIntegerDigits,
         minimumFractionDigits: internals.minimumFractionDigits,
         maximumFractionDigits: internals.maximumFractionDigits,
     };
 
     // Min/Max significant digits are either both present or not at all.
     assert(hasOwn("minimumSignificantDigits", internals) ===
            hasOwn("maximumSignificantDigits", internals),
@@ -257,10 +243,24 @@ function Intl_PluralRules_resolvedOption
     if (hasOwn("minimumSignificantDigits", internals)) {
         _DefineDataProperty(result, "minimumSignificantDigits",
                             internals.minimumSignificantDigits);
         _DefineDataProperty(result, "maximumSignificantDigits",
                             internals.maximumSignificantDigits);
     }
 
     // Step 6.
+    var internalsPluralCategories = internals.pluralCategories;
+    if (internalsPluralCategories === null) {
+        internalsPluralCategories = intl_GetPluralCategories(pluralRules);
+        internals.pluralCategories = internalsPluralCategories;
+    }
+
+    var pluralCategories = [];
+    for (var i = 0; i < internalsPluralCategories.length; i++)
+        _DefineDataProperty(pluralCategories, i, internalsPluralCategories[i]);
+
+    // Step 7.
+    _DefineDataProperty(result, "pluralCategories", pluralCategories);
+
+    // Step 8.
     return result;
 }

--- a/js/src/builtin/intl/RelativeTimeFormat.js
+++ b/js/src/builtin/intl/RelativeTimeFormat.js
@@ -214,17 +214,17 @@ function Intl_RelativeTimeFormat_format(
         ThrowRangeError(JSMSG_INVALID_OPTION_VALUE, "unit", u);
     }
 
     // Step 5.
     return intl_FormatRelativeTime(relativeTimeFormat, t, u, internals.numeric);
 }
 
 /**
- * Returns the resolved options for a PluralRules object.
+ * Returns the resolved options for a RelativeTimeFormat object.
  *
  * Spec: ECMAScript 402 API, RelativeTimeFormat, 1.4.4.
  */
 function Intl_RelativeTimeFormat_resolvedOptions() {
     var relativeTimeFormat;
     // Check "this RelativeTimeFormat object" per introduction of section 1.4.
     if (!IsObject(this) || (relativeTimeFormat = GuardToRelativeTimeFormat(this)) === null) {
         ThrowTypeError(JSMSG_INTL_OBJECT_NOT_INITED, "RelativeTimeFormat", "resolvedOptions",

--- a/js/src/ctypes/CTypes.cpp
+++ b/js/src/ctypes/CTypes.cpp
@@ -6803,33 +6803,45 @@ GetABI(JSContext* cx, HandleValue abiTyp
   // given platform. ABI_DEFAULT specifies the default
   // C calling convention (cdecl) on each platform.
   switch (abi) {
   case ABI_DEFAULT:
     *result = FFI_DEFAULT_ABI;
     return true;
   case ABI_THISCALL:
 #if defined(_WIN64)
+#if defined(_M_X64)
     *result = FFI_WIN64;
+#elif defined(_M_ARM64)
+    *result = FFI_SYSV;
+#else
+#error unknown 64-bit Windows platform
+#endif
     return true;
 #elif defined(_WIN32)
     *result = FFI_THISCALL;
     return true;
 #else
     break;
 #endif
   case ABI_STDCALL:
   case ABI_WINAPI:
 #if (defined(_WIN32) && !defined(_WIN64)) || defined(_OS2)
     *result = FFI_STDCALL;
     return true;
 #elif (defined(_WIN64))
     // We'd like the same code to work across Win32 and Win64, so stdcall_api
     // and winapi_abi become aliases to the lone Win64 ABI.
+#if defined(_M_X64)
     *result = FFI_WIN64;
+#elif defined(_M_ARM64)
+    *result = FFI_SYSV;
+#else
+#error unknown 64-bit Windows platform
+#endif
     return true;
 #endif
   case INVALID_ABI:
     break;
   }
   return false;
 }
 

--- a/js/src/ctypes/libffi/src/aarch64/ffi.c
+++ b/js/src/ctypes/libffi/src/aarch64/ffi.c
@@ -21,16 +21,23 @@ SOFTWARE OR THE USE OR OTHER DEALINGS IN
 
 #include <stdio.h>
 
 #include <ffi.h>
 #include <ffi_common.h>
 
 #include <stdlib.h>
 
+#if defined(_WIN32)
+#if !defined(WIN32_LEAN_AND_MEAN)
+#define WIN32_LEAN_AND_MEAN
+#endif
+#include <windows.h>
+#endif
+
 /* Stack alignment requirement in bytes */
 #if defined (__APPLE__)
 #define AARCH64_STACK_ALIGN 1
 #else
 #define AARCH64_STACK_ALIGN 16
 #endif
 
 #define N_X_ARG_REG 8
@@ -60,16 +67,19 @@ sys_icache_invalidate (void *start, size
 
 static inline void
 ffi_clear_cache (void *start, void *end)
 {
 #if defined (__clang__) && defined (__APPLE__)
 	sys_icache_invalidate (start, (char *)end - (char *)start);
 #elif defined (__GNUC__)
 	__builtin___clear_cache (start, end);
+#elif defined (_WIN32)
+	FlushInstructionCache (GetCurrentProcess (), start,
+			       (char*)end - (char*)start);
 #else
 #error "Missing builtin to flush instruction cache"
 #endif
 }
 
 static void *
 get_x_addr (struct call_context *context, unsigned n)
 {
@@ -214,16 +224,20 @@ get_basic_type_size (unsigned short type
       return sizeof (SINT64);
 
     default:
       FFI_ASSERT (0);
       return 0;
     }
 }
 
+// XXX The Win64 and the SYSV ABI are very close, differing only in their
+// calling of varargs functions.  Since we don't care about calling varargs
+// functions in our use of libffi, we just hack our way through and use the
+// SYSV-designated functions everywhere.
 extern void
 ffi_call_SYSV (unsigned (*)(struct call_context *context, unsigned char *,
 			    extended_cif *),
                struct call_context *context,
                extended_cif *,
                size_t,
                void (*fn)(void));
 
@@ -486,17 +500,17 @@ allocate_to_stack (struct arg_state *sta
   state->nsaa = ALIGN (state->nsaa, alignment);
 #if defined (__APPLE__)
   if (state->allocating_variadic)
     state->nsaa = ALIGN (state->nsaa, 8);
 #else
   state->nsaa = ALIGN (state->nsaa, 8);
 #endif
 
-  allocation = stack + state->nsaa;
+  allocation = (char*)stack + state->nsaa;
 
   state->nsaa += size;
   return allocation;
 }
 
 static void
 copy_basic_type (void *dest, void *source, unsigned short type)
 {
@@ -570,17 +584,17 @@ copy_hfa_to_reg_or_stack (void *memory,
   else
     {
       int i;
       unsigned short type = get_homogeneous_type (ty);
       for (i = 0; i < elems; i++)
 	{
 	  void *reg = allocate_to_v (context, state);
 	  copy_basic_type (reg, memory, type);
-	  memory += get_basic_type_size (type);
+	  memory = (char*)memory + get_basic_type_size (type);
 	}
     }
 }
 
 /* Either allocate an appropriate register for the argument type, or if
    none are available, allocate a stack slot and return a pointer
    to the allocated space.  */
 
@@ -854,17 +868,17 @@ ffi_call (ffi_cif *cif, void (*fn)(void)
 		  {
 		    int j;
 		    unsigned short type = get_homogeneous_type (cif->rtype);
 		    unsigned elems = element_count (cif->rtype);
 		    for (j = 0; j < elems; j++)
 		      {
 			void *reg = get_basic_type_addr (type, &context, j);
 			copy_basic_type (rvalue, reg, type);
-			rvalue += get_basic_type_size (type);
+			rvalue = (char*)rvalue + get_basic_type_size (type);
 		      }
 		  }
                 else if ((cif->rtype->size + 7) / 8 < N_X_ARG_REG)
                   {
                     size_t size = ALIGN (cif->rtype->size, sizeof (UINT64));
                     memcpy (rvalue, get_x_addr (&context, 0), size);
                   }
                 else
@@ -897,26 +911,27 @@ static unsigned char trampoline [] =
 { 0x70, 0x00, 0x00, 0x58,	/* ldr	x16, 1f	*/
   0x91, 0x00, 0x00, 0x10,	/* adr	x17, 2f	*/
   0x00, 0x02, 0x1f, 0xd6	/* br	x16	*/
 };
 
 /* Build a trampoline.  */
 
 #define FFI_INIT_TRAMPOLINE(TRAMP,FUN,CTX,FLAGS)			\
-  ({unsigned char *__tramp = (unsigned char*)(TRAMP);			\
+  do {									\
+    unsigned char *__tramp = (unsigned char*)(TRAMP);			\
     UINT64  __fun = (UINT64)(FUN);					\
     UINT64  __ctx = (UINT64)(CTX);					\
     UINT64  __flags = (UINT64)(FLAGS);					\
     memcpy (__tramp, trampoline, sizeof (trampoline));			\
     memcpy (__tramp + 12, &__fun, sizeof (__fun));			\
     memcpy (__tramp + 20, &__ctx, sizeof (__ctx));			\
     memcpy (__tramp + 28, &__flags, sizeof (__flags));			\
     ffi_clear_cache(__tramp, __tramp + FFI_TRAMPOLINE_SIZE);		\
-  })
+  } while(0)
 
 ffi_status
 ffi_prep_closure_loc (ffi_closure* closure,
                       ffi_cif* cif,
                       void (*fun)(ffi_cif*,void*,void**,void*),
                       void *user_data,
                       void *codeloc)
 {
@@ -1136,17 +1151,17 @@ ffi_closure_SYSV_inner (ffi_closure *clo
 	    {
 	      int j;
 	      unsigned short type = get_homogeneous_type (cif->rtype);
 	      unsigned elems = element_count (cif->rtype);
 	      for (j = 0; j < elems; j++)
 		{
 		  void *reg = get_basic_type_addr (type, context, j);
 		  copy_basic_type (reg, rvalue, type);
-		  rvalue += get_basic_type_size (type);
+		  rvalue = (char*)rvalue + get_basic_type_size (type);
 		}
 	    }
           else if ((cif->rtype->size + 7) / 8 < N_X_ARG_REG)
             {
               size_t size = ALIGN (cif->rtype->size, sizeof (UINT64)) ;
               memcpy (get_x_addr (context, 0), rvalue, size);
             }
           else

new file mode 100644
--- /dev/null
+++ b/js/src/ctypes/libffi/src/aarch64/win64.asm
@@ -0,0 +1,272 @@
+;; Copyright (c) 2009, 2010, 2011, 2012 ARM Ltd.
+
+;; Permission is hereby granted, free of charge, to any person obtaining
+;; a copy of this software and associated documentation files (the
+;; ``Software''), to deal in the Software without restriction, including
+;; without limitation the rights to use, copy, modify, merge, publish,
+;; distribute, sublicense, and/or sell copies of the Software, and to
+;; permit persons to whom the Software is furnished to do so, subject to
+;; the following conditions:
+
+;; The above copyright notice and this permission notice shall be
+;; included in all copies or substantial portions of the Software.
+
+;; THE SOFTWARE IS PROVIDED ``AS IS'', WITHOUT WARRANTY OF ANY KIND,
+;; EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+;; MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+;; IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+;; CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+;; TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+;; SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+;; Hand-converted from the sysv.S file in this directory.
+
+        AREA |.text|, CODE, ARM64
+
+   ;; ffi_call_SYSV()
+
+   ;; Create a stack frame, setup an argument context, call the callee
+   ;; and extract the result.
+
+   ;; The maximum required argument stack size is provided,
+   ;; ffi_call_SYSV() allocates that stack space then calls the
+   ;; prepare_fn to populate register context and stack.  The
+   ;; argument passing registers are loaded from the register
+   ;; context and the callee called, on return the register passing
+   ;; register are saved back to the context.  Our caller will
+   ;; extract the return value from the final state of the saved
+   ;; register context.
+
+   ;; Prototype:
+
+   ;; extern unsigned
+   ;; ffi_call_SYSV (void (*)(struct call_context *context, unsigned char *,
+   ;; 			   extended_cif *),
+   ;;                struct call_context *context,
+   ;;                extended_cif *,
+   ;;                size_t required_stack_size,
+   ;;                void (*fn)(void));
+
+   ;; Therefore on entry we have:
+
+   ;; x0 prepare_fn
+   ;; x1 &context
+   ;; x2 &ecif
+   ;; x3 bytes
+   ;; x4 fn
+
+   ;; This function uses the following stack frame layout:
+
+   ;; ==
+   ;;              saved x30(lr)
+   ;; x29(fp)->    saved x29(fp)
+   ;;              saved x24
+   ;;              saved x23
+   ;;              saved x22
+   ;; sp'    ->    saved x21
+   ;;              ...
+   ;; sp     ->    (constructed callee stack arguments)
+   ;; ==
+
+   ;; Voila!
+
+	EXPORT |ffi_call_SYSV|
+
+|ffi_call_SYSV| PROC
+;#define ffi_call_SYSV_FS (8 * 4)
+
+        stp     x29, x30, [sp, #-16]!
+
+        mov     x29, sp
+        sub     sp, sp, #32 	; ffi_call_SYSV_FS
+
+        stp     x21, x22, [sp, #0]
+        stp     x23, x24, [sp, #16]
+
+        mov     x21, x1
+        mov     x22, x2
+        mov     x24, x4
+
+        ; Allocate the stack space for the actual arguments, many
+        ; arguments will be passed in registers, but we assume
+        ; worst case and allocate sufficient stack for ALL of
+        ; the arguments.
+        sub     sp, sp, x3
+
+        ; unsigned (*prepare_fn) (struct call_context *context,
+        ;                         unsigned char *stack, extended_cif *ecif);
+
+        mov     x23, x0
+        mov     x0, x1
+        mov     x1, sp
+        ; x2 already in place
+        blr     x23
+
+        ; Preserve the flags returned.
+        mov     x23, x0
+
+        ; Figure out if we should touch the vector registers.
+        tbz     x23, #0, noload_call
+
+        ; Load the vector argument passing registers.
+        ldp     q0, q1, [x21, #8*32 +  0]
+        ldp     q2, q3, [x21, #8*32 + 32]
+        ldp     q4, q5, [x21, #8*32 + 64]
+        ldp     q6, q7, [x21, #8*32 + 96]
+
+noload_call
+        ; Load the core argument passing registers.
+        ldp     x0, x1, [x21,  #0]
+        ldp     x2, x3, [x21, #16]
+        ldp     x4, x5, [x21, #32]
+        ldp     x6, x7, [x21, #48]
+
+        ; Don't forget x8 which may be holding the address of a return buffer.
+        ldr     x8,     [x21, #8*8]
+
+        blr     x24
+
+        ; Save the core argument passing registers.
+        stp     x0, x1, [x21,  #0]
+        stp     x2, x3, [x21, #16]
+        stp     x4, x5, [x21, #32]
+        stp     x6, x7, [x21, #48]
+
+        ; Note nothing useful ever comes back in x8!
+
+        ; Figure out if we should touch the vector registers.
+        tbz     x23, #0, nosave_call ; AARCH64_FFI_WITH_V_BIT
+
+        ; Save the vector argument passing registers.
+        stp     q0, q1, [x21, #8*32 + 0]
+        stp     q2, q3, [x21, #8*32 + 32]
+        stp     q4, q5, [x21, #8*32 + 64]
+        stp     q6, q7, [x21, #8*32 + 96]
+
+nosave_call
+        ; All done, unwind our stack frame.
+        ldp     x21, x22, [x29,  # - 32] ; ffi_call_SYSV_FS
+
+        ldp     x23, x24, [x29,  # - 32 + 16] ; ffi_call_SYSV_FS
+
+        mov     sp, x29
+
+        ldp     x29, x30, [sp], #16
+
+        ret
+
+	ENDP
+
+; #define ffi_closure_SYSV_FS (8 * 2 + AARCH64_CALL_CONTEXT_SIZE)
+
+   ;; ffi_closure_SYSV
+
+   ;; Closure invocation glue. This is the low level code invoked directly by
+   ;; the closure trampoline to setup and call a closure.
+
+   ;; On entry x17 points to a struct trampoline_data, x16 has been clobbered
+   ;; all other registers are preserved.
+
+   ;; We allocate a call context and save the argument passing registers,
+   ;; then invoked the generic C ffi_closure_SYSV_inner() function to do all
+   ;; the real work, on return we load the result passing registers back from
+   ;; the call context.
+
+   ;; On entry
+
+   ;; extern void
+   ;; ffi_closure_SYSV (struct trampoline_data *);
+
+   ;; struct trampoline_data
+   ;; {
+   ;;      UINT64 *ffi_closure;
+   ;;      UINT64 flags;
+   ;; };
+
+   ;; This function uses the following stack frame layout:
+
+   ;; ==
+   ;;              saved x30(lr)
+   ;; x29(fp)->    saved x29(fp)
+   ;;              saved x22
+   ;;              saved x21
+   ;;              ...
+   ;; sp     ->    call_context
+   ;; ==
+
+   ;; Voila!
+
+	IMPORT |ffi_closure_SYSV_inner|
+	EXPORT |ffi_closure_SYSV|
+
+|ffi_closure_SYSV| PROC
+        stp     x29, x30, [sp, #-16]!
+
+        mov     x29, sp
+
+        sub     sp, sp, #256+512+16
+
+        stp     x21, x22, [x29, #-16]
+
+        ; Load x21 with &call_context.
+        mov     x21, sp
+        ; Preserve our struct trampoline_data
+        mov     x22, x17
+
+        ; Save the rest of the argument passing registers.
+        stp     x0, x1, [x21, #0]
+        stp     x2, x3, [x21, #16]
+        stp     x4, x5, [x21, #32]
+        stp     x6, x7, [x21, #48]
+        ; Don't forget we may have been given a result scratch pad address.
+        str     x8,     [x21, #64]
+
+        ; Figure out if we should touch the vector registers.
+        ldr     x0, [x22, #8]
+        tbz     x0, #0, nosave_closure ; AARCH64_FFI_WITH_V_BIT
+
+        ; Save the argument passing vector registers.
+        stp     q0, q1, [x21, #8*32 + 0]
+        stp     q2, q3, [x21, #8*32 + 32]
+        stp     q4, q5, [x21, #8*32 + 64]
+        stp     q6, q7, [x21, #8*32 + 96]
+
+nosave_closure
+        ; Load &ffi_closure..
+        ldr     x0, [x22, #0]
+        mov     x1, x21
+        ; Compute the location of the stack at the point that the
+        ; trampoline was called.
+        add     x2, x29, #16
+
+        bl      ffi_closure_SYSV_inner
+
+        ; Figure out if we should touch the vector registers.
+        ldr     x0, [x22, #8]
+        tbz     x0, #0, noload_closure ; AARCH64_FFI_WITH_V_BIT
+
+        ; Load the result passing vector registers.
+        ldp     q0, q1, [x21, #8*32 + 0]
+        ldp     q2, q3, [x21, #8*32 + 32]
+        ldp     q4, q5, [x21, #8*32 + 64]
+        ldp     q6, q7, [x21, #8*32 + 96]
+
+noload_closure
+        ; Load the result passing core registers.
+        ldp     x0, x1, [x21,  #0]
+        ldp     x2, x3, [x21, #16]
+        ldp     x4, x5, [x21, #32]
+        ldp     x6, x7, [x21, #48]
+        ; Note nothing useful is returned in x8.
+
+        ; We are done, unwind our frame.
+        ldp     x21, x22, [x29,  #-16]
+
+        mov     sp, x29
+
+        ldp     x29, x30, [sp], #16
+
+        ret
+
+	ENDP
+	END

--- a/js/src/jit-test/jit_test.py
+++ b/js/src/jit-test/jit_test.py
@@ -370,19 +370,23 @@ def main(argv):
         elif options.debugger == 'lldb':
             debug_cmd = ['lldb', '--']
         elif options.debugger == 'rr':
             debug_cmd = ['rr', 'record']
         else:
             debug_cmd = options.debugger.split()
 
         with change_env(test_environment):
-            subprocess.call(debug_cmd + tc.command(prefix, jittests.LIB_DIR, jittests.MODULE_DIR))
             if options.debugger == 'rr':
-                subprocess.call(['rr', 'replay'])
+                subprocess.call(debug_cmd +
+                                tc.command(prefix, jittests.LIB_DIR, jittests.MODULE_DIR))
+                os.execvp('rr', ['rr', 'replay'])
+            else:
+                os.execvp(debug_cmd[0], debug_cmd +
+                          tc.command(prefix, jittests.LIB_DIR, jittests.MODULE_DIR))
         sys.exit()
 
     try:
         ok = None
         if options.remote:
             ok = jittests.run_tests(job_list, job_count, prefix, options, remote=True)
         else:
             with change_env(test_environment):

--- a/js/src/jit/JitRealm.h
+++ b/js/src/jit/JitRealm.h
@@ -633,44 +633,40 @@ const unsigned WINDOWS_BIG_FRAME_TOUCH_I
 // AutoWritableJitCodeFallible may only fail to make code writable; it cannot fail to
 // make JIT code executable (because the creating code has no chance to
 // recover from a failed destructor).
 class MOZ_RAII AutoWritableJitCodeFallible
 {
     JSRuntime* rt_;
     void* addr_;
     size_t size_;
-    bool madeWritable_;
 
   public:
     AutoWritableJitCodeFallible(JSRuntime* rt, void* addr, size_t size)
-      : rt_(rt), addr_(addr), size_(size), madeWritable_(false)
+      : rt_(rt), addr_(addr), size_(size)
     {
         rt_->toggleAutoWritableJitCodeActive(true);
     }
 
     AutoWritableJitCodeFallible(void* addr, size_t size)
       : AutoWritableJitCodeFallible(TlsContext.get()->runtime(), addr, size)
     {
     }
 
     explicit AutoWritableJitCodeFallible(JitCode* code)
       : AutoWritableJitCodeFallible(code->runtimeFromMainThread(), code->raw(), code->bufferSize())
     {}
 
     MOZ_MUST_USE bool makeWritable() {
-        madeWritable_ = ExecutableAllocator::makeWritable(addr_, size_);
-        return madeWritable_;
+        return ExecutableAllocator::makeWritable(addr_, size_);
     }
 
     ~AutoWritableJitCodeFallible() {
-        if (madeWritable_) {
-            if (!ExecutableAllocator::makeExecutable(addr_, size_)) {
-                MOZ_CRASH();
-            }
+        if (!ExecutableAllocator::makeExecutable(addr_, size_)) {
+            MOZ_CRASH();
         }
         rt_->toggleAutoWritableJitCodeActive(false);
     }
 
 };
 
 // Infallible variant of AutoWritableJitCodeFallible, ensures writable during construction
 class MOZ_RAII AutoWritableJitCode : private AutoWritableJitCodeFallible

new file mode 100644
--- /dev/null
+++ b/js/src/jit/moz.build
@@ -0,0 +1,239 @@
+# -*- 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/.
+
+FINAL_LIBRARY = 'js'
+
+FILES_PER_UNIFIED_FILE = 6
+
+# Includes should be relative to parent path
+LOCAL_INCLUDES += [
+    '!..',
+    '..'
+]
+
+include('../js-config.mozbuild')
+include('../js-cxxflags.mozbuild')
+
+
+# Generate jit/MOpcodes.h from jit/MIR.h
+GENERATED_FILES += ['MOpcodes.h']
+MOpcodesGenerated = GENERATED_FILES['MOpcodes.h']
+MOpcodesGenerated.script = 'GenerateOpcodeFiles.py:generate_mir_header'
+MOpcodesGenerated.inputs = ['MIR.h']
+
+# Generate jit/LOpcodes.h from jit/LIR.h, jit/shared/LIR-shared.h, and
+# platform-specific LIR files.
+GENERATED_FILES += ['LOpcodes.h']
+LOpcodesGenerated = GENERATED_FILES['LOpcodes.h']
+LOpcodesGenerated.script = 'GenerateOpcodeFiles.py:generate_lir_header'
+LOpcodesGenerated.inputs = ['LIR.h', 'shared/LIR-shared.h']
+
+
+UNIFIED_SOURCES += [
+    'AliasAnalysis.cpp',
+    'AlignmentMaskAnalysis.cpp',
+    'BacktrackingAllocator.cpp',
+    'Bailouts.cpp',
+    'BaselineBailouts.cpp',
+    'BaselineCacheIRCompiler.cpp',
+    'BaselineCompiler.cpp',
+    'BaselineDebugModeOSR.cpp',
+    'BaselineFrame.cpp',
+    'BaselineFrameInfo.cpp',
+    'BaselineIC.cpp',
+    'BaselineInspector.cpp',
+    'BaselineJIT.cpp',
+    'BitSet.cpp',
+    'BytecodeAnalysis.cpp',
+    'CacheIR.cpp',
+    'CacheIRCompiler.cpp',
+    'CacheIRSpewer.cpp',
+    'CodeGenerator.cpp',
+    'CompileWrappers.cpp',
+    'EdgeCaseAnalysis.cpp',
+    'EffectiveAddressAnalysis.cpp',
+    'ExecutableAllocator.cpp',
+    'FoldLinearArithConstants.cpp',
+    'InstructionReordering.cpp',
+    'Ion.cpp',
+    'IonAnalysis.cpp',
+    'IonBuilder.cpp',
+    'IonCacheIRCompiler.cpp',
+    'IonControlFlow.cpp',
+    'IonIC.cpp',
+    'IonOptimizationLevels.cpp',
+    'Jit.cpp',
+    'JitcodeMap.cpp',
+    'JitFrames.cpp',
+    'JitOptions.cpp',
+    'JitSpewer.cpp',
+    'JSJitFrameIter.cpp',
+    'JSONSpewer.cpp',
+    'LICM.cpp',
+    'Linker.cpp',
+    'LIR.cpp',
+    'LoopUnroller.cpp',
+    'Lowering.cpp',
+    'MacroAssembler.cpp',
+    'MCallOptimize.cpp',
+    'MIR.cpp',
+    'MIRGraph.cpp',
+    'MoveResolver.cpp',
+    'OptimizationTracking.cpp',
+    'PerfSpewer.cpp',
+    'ProcessExecutableMemory.cpp',
+    'RangeAnalysis.cpp',
+    'Recover.cpp',
+    'RegisterAllocator.cpp',
+    'RematerializedFrame.cpp',
+    'Safepoints.cpp',
+    'ScalarReplacement.cpp',
+    'shared/Assembler-shared.cpp',
+    'shared/CodeGenerator-shared.cpp',
+    'shared/Disassembler-shared.cpp',
+    'shared/Lowering-shared.cpp',
+    'Sink.cpp',
+    'Snapshots.cpp',
+    'StupidAllocator.cpp',
+    'TypedObjectPrediction.cpp',
+    'TypePolicy.cpp',
+    'ValueNumbering.cpp',
+    'VMFunctions.cpp',
+    'WasmBCE.cpp',
+]
+
+if not CONFIG['ENABLE_ION']:
+    LOpcodesGenerated.inputs += ['none/LIR-none.h']
+    UNIFIED_SOURCES += [
+        'none/Trampoline-none.cpp'
+    ]
+elif CONFIG['JS_CODEGEN_X86'] or CONFIG['JS_CODEGEN_X64']:
+    LOpcodesGenerated.inputs += ['x86-shared/LIR-x86-shared.h']
+    UNIFIED_SOURCES += [
+        'x86-shared/Architecture-x86-shared.cpp',
+        'x86-shared/Assembler-x86-shared.cpp',
+        'x86-shared/AssemblerBuffer-x86-shared.cpp',
+        'x86-shared/CodeGenerator-x86-shared.cpp',
+        'x86-shared/Lowering-x86-shared.cpp',
+        'x86-shared/MacroAssembler-x86-shared-SIMD.cpp',
+        'x86-shared/MacroAssembler-x86-shared.cpp',
+        'x86-shared/MoveEmitter-x86-shared.cpp',
+    ]
+    if CONFIG['JS_CODEGEN_X64']:
+        LOpcodesGenerated.inputs += ['x64/LIR-x64.h']
+        UNIFIED_SOURCES += [
+            'x64/Assembler-x64.cpp',
+            'x64/Bailouts-x64.cpp',
+            'x64/CodeGenerator-x64.cpp',
+            'x64/Lowering-x64.cpp',
+            'x64/MacroAssembler-x64.cpp',
+            'x64/Trampoline-x64.cpp',
+        ]
+    else:
+        LOpcodesGenerated.inputs += ['x86/LIR-x86.h']
+        UNIFIED_SOURCES += [
+            'x86/Assembler-x86.cpp',
+            'x86/Bailouts-x86.cpp',
+            'x86/CodeGenerator-x86.cpp',
+            'x86/Lowering-x86.cpp',
+            'x86/MacroAssembler-x86.cpp',
+            'x86/Trampoline-x86.cpp',
+        ]
+elif CONFIG['JS_CODEGEN_ARM']:
+    LOpcodesGenerated.inputs += ['arm/LIR-arm.h']
+    UNIFIED_SOURCES += [
+        'arm/Architecture-arm.cpp',
+        'arm/Assembler-arm.cpp',
+        'arm/Bailouts-arm.cpp',
+        'arm/CodeGenerator-arm.cpp',
+        'arm/disasm/Constants-arm.cpp',
+        'arm/disasm/Disasm-arm.cpp',
+        'arm/Lowering-arm.cpp',
+        'arm/MacroAssembler-arm.cpp',
+        'arm/MoveEmitter-arm.cpp',
+        'arm/Trampoline-arm.cpp',
+    ]
+    if CONFIG['JS_SIMULATOR_ARM']:
+        UNIFIED_SOURCES += [
+            'arm/Simulator-arm.cpp'
+        ]
+    elif CONFIG['OS_ARCH'] == 'Darwin':
+        SOURCES += [
+            'arm/llvm-compiler-rt/arm/aeabi_idivmod.S',
+            'arm/llvm-compiler-rt/arm/aeabi_uidivmod.S',
+        ]
+elif CONFIG['JS_CODEGEN_ARM64']:
+    LOpcodesGenerated.inputs += ['arm64/LIR-arm64.h']
+    UNIFIED_SOURCES += [
+        'arm64/Architecture-arm64.cpp',
+        'arm64/Assembler-arm64.cpp',
+        'arm64/Bailouts-arm64.cpp',
+        'arm64/CodeGenerator-arm64.cpp',
+        'arm64/Lowering-arm64.cpp',
+        'arm64/MacroAssembler-arm64.cpp',
+        'arm64/MoveEmitter-arm64.cpp',
+        'arm64/Trampoline-arm64.cpp',
+        'arm64/vixl/Assembler-vixl.cpp',
+        'arm64/vixl/Cpu-vixl.cpp',
+        'arm64/vixl/Decoder-vixl.cpp',
+        'arm64/vixl/Disasm-vixl.cpp',
+        'arm64/vixl/Instructions-vixl.cpp',
+        'arm64/vixl/Instrument-vixl.cpp',
+        'arm64/vixl/MacroAssembler-vixl.cpp',
+        'arm64/vixl/MozAssembler-vixl.cpp',
+        'arm64/vixl/MozInstructions-vixl.cpp',
+        'arm64/vixl/Utils-vixl.cpp'
+    ]
+    if CONFIG['JS_SIMULATOR_ARM64']:
+        UNIFIED_SOURCES += [
+            'arm64/vixl/Debugger-vixl.cpp',
+            'arm64/vixl/Logic-vixl.cpp',
+            'arm64/vixl/MozSimulator-vixl.cpp',
+            'arm64/vixl/Simulator-vixl.cpp'
+        ]
+elif CONFIG['JS_CODEGEN_MIPS32'] or CONFIG['JS_CODEGEN_MIPS64']:
+    LOpcodesGenerated.inputs += ['mips-shared/LIR-mips-shared.h']
+    UNIFIED_SOURCES += [
+        'mips-shared/Architecture-mips-shared.cpp',
+        'mips-shared/Assembler-mips-shared.cpp',
+        'mips-shared/Bailouts-mips-shared.cpp',
+        'mips-shared/CodeGenerator-mips-shared.cpp',
+        'mips-shared/Lowering-mips-shared.cpp',
+        'mips-shared/MacroAssembler-mips-shared.cpp',
+        'mips-shared/MoveEmitter-mips-shared.cpp',
+    ]
+    if CONFIG['JS_CODEGEN_MIPS32']:
+        LOpcodesGenerated.inputs += ['mips32/LIR-mips32.h']
+        UNIFIED_SOURCES += [
+            'mips32/Architecture-mips32.cpp',
+            'mips32/Assembler-mips32.cpp',
+            'mips32/Bailouts-mips32.cpp',
+            'mips32/CodeGenerator-mips32.cpp',
+            'mips32/Lowering-mips32.cpp',
+            'mips32/MacroAssembler-mips32.cpp',
+            'mips32/MoveEmitter-mips32.cpp',
+            'mips32/Trampoline-mips32.cpp',
+        ]
+        if CONFIG['JS_SIMULATOR_MIPS32']:
+            UNIFIED_SOURCES += [
+                'mips32/Simulator-mips32.cpp'
+            ]
+    elif CONFIG['JS_CODEGEN_MIPS64']:
+        LOpcodesGenerated.inputs += ['mips64/LIR-mips64.h']
+        UNIFIED_SOURCES += [
+            'mips64/Architecture-mips64.cpp',
+            'mips64/Assembler-mips64.cpp',
+            'mips64/Bailouts-mips64.cpp',
+            'mips64/CodeGenerator-mips64.cpp',
+            'mips64/Lowering-mips64.cpp',
+            'mips64/MacroAssembler-mips64.cpp',
+            'mips64/MoveEmitter-mips64.cpp',
+            'mips64/Trampoline-mips64.cpp',
+        ]
+        if CONFIG['JS_SIMULATOR_MIPS64']:
+            UNIFIED_SOURCES += [
+                'mips64/Simulator-mips64.cpp'
+            ]
\ No newline at end of file

--- a/js/src/jsapi-tests/moz.build
+++ b/js/src/jsapi-tests/moz.build
@@ -136,16 +136,17 @@ if CONFIG['ENABLE_ION']:
         'testJitRegisterSet.cpp',
         'testJitRValueAlloc.cpp',
     ]
 
 if CONFIG['NIGHTLY_BUILD']:
     # The Error interceptor only exists on Nightly.
     UNIFIED_SOURCES += [
         'testErrorInterceptor.cpp',
+        'testErrorInterceptorGC.cpp',
     ]
 
 if CONFIG['JS_BUILD_BINAST'] and CONFIG['JS_STANDALONE'] and not CONFIG['FUZZING']:
     # Standalone builds leave the source directory untouched,
     # which lets us run tests with the data files intact.
     # Otherwise, in the current state of the build system,
     # we can't have data files in js/src tests.
     # Also, fuzzing builds modify the const matching in the

--- a/js/src/jsapi-tests/testErrorInterceptor.cpp
+++ b/js/src/jsapi-tests/testErrorInterceptor.cpp
@@ -7,17 +7,17 @@
 // Tests for JS_GetErrorInterceptorCallback and JS_SetErrorInterceptorCallback.
 
 
 namespace {
 static JS::PersistentRootedString gLatestMessage;
 
 // An interceptor that stores the error in `gLatestMessage`.
 struct SimpleInterceptor: JSErrorInterceptor {
-    virtual void interceptError(JSContext* cx, const JS::Value& val) override {
+    virtual void interceptError(JSContext* cx, JS::HandleValue val) override {
         js::StringBuffer buffer(cx);
         if (!ValueToStringBuffer(cx, val, buffer)) {
             MOZ_CRASH("Could not convert to string buffer");
         }
         gLatestMessage = buffer.finishString();
         if (!gLatestMessage) {
             MOZ_CRASH("Could not convert to string");
         }

new file mode 100644
--- /dev/null
+++ b/js/src/jsapi-tests/testErrorInterceptorGC.cpp
@@ -0,0 +1,34 @@
+#include "jsapi.h"
+
+#include "jsapi-tests/tests.h"
+
+namespace {
+
+// An interceptor that triggers GC:
+struct ErrorInterceptorWithGC : JSErrorInterceptor {
+    void interceptError(JSContext* cx, JS::HandleValue val) override {
+        JS::PrepareForFullGC(cx);
+        JS::NonIncrementalGC(cx, GC_SHRINK, JS::gcreason::DEBUG_GC);
+    }
+};
+
+}
+
+BEGIN_TEST(testErrorInterceptorGC)
+{
+    JSErrorInterceptor* original = JS_GetErrorInterceptorCallback(cx->runtime());
+
+    ErrorInterceptorWithGC interceptor;
+    JS_SetErrorInterceptorCallback(cx->runtime(), &interceptor);
+
+    CHECK(!execDontReport("0 = 0;", __FILE__, __LINE__));
+
+    CHECK(JS_IsExceptionPending(cx));
+    JS_ClearPendingException(cx);
+
+    // Restore the original error interceptor.
+    JS_SetErrorInterceptorCallback(cx->runtime(), original);
+
+    return true;
+}
+END_TEST(testErrorInterceptorGC)

--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -257,17 +257,17 @@ using JSExternalStringSizeofCallback =
  * Callback used to intercept JavaScript errors.
  */
 struct JSErrorInterceptor {
     /**
      * This method is called whenever an error has been raised from JS code.
      *
      * This method MUST be infallible.
      */
-    virtual void interceptError(JSContext* cx, const JS::Value& error) = 0;
+    virtual void interceptError(JSContext* cx, JS::HandleValue error) = 0;
 };
 
 /************************************************************************/
 
 static MOZ_ALWAYS_INLINE JS::Value
 JS_NumberValue(double d)
 {
     int32_t i;

--- a/js/src/moz.build
+++ b/js/src/moz.build
@@ -93,29 +93,16 @@ CONFIGURE_DEFINE_FILES += [
     'js-config.h',
 ]
 
 if CONFIG['HAVE_DTRACE']:
     GENERATED_FILES += ['javascript-trace.h']
 
     EXPORTS += ['!javascript-trace.h']
 
-# Generate jit/MOpcodes.h from jit/MIR.h
-GENERATED_FILES += ['jit/MOpcodes.h']
-MOpcodesGenerated = GENERATED_FILES['jit/MOpcodes.h']
-MOpcodesGenerated.script = 'jit/GenerateOpcodeFiles.py:generate_mir_header'
-MOpcodesGenerated.inputs = ['jit/MIR.h']
-
-# Generate jit/LOpcodes.h from jit/LIR.h, jit/shared/LIR-shared.h, and
-# platform-specific LIR files.
-GENERATED_FILES += ['jit/LOpcodes.h']
-LOpcodesGenerated = GENERATED_FILES['jit/LOpcodes.h']
-LOpcodesGenerated.script = 'jit/GenerateOpcodeFiles.py:generate_lir_header'
-LOpcodesGenerated.inputs = ['jit/LIR.h', 'jit/shared/LIR-shared.h']
-
 # Changes to internal header files, used externally, massively slow down
 # browser builds.  Don't add new files here unless you know what you're
 # doing!
 EXPORTS += [
     '!js-config.h',
     'js.msg',
     'jsapi.h',
     'jsfriendapi.h',
@@ -266,86 +253,16 @@ UNIFIED_SOURCES += [
     'irregexp/NativeRegExpMacroAssembler.cpp',
     'irregexp/RegExpAST.cpp',
     'irregexp/RegExpCharacters.cpp',
     'irregexp/RegExpEngine.cpp',
     'irregexp/RegExpInterpreter.cpp',
     'irregexp/RegExpMacroAssembler.cpp',
     'irregexp/RegExpParser.cpp',
     'irregexp/RegExpStack.cpp',
-    'jit/AliasAnalysis.cpp',
-    'jit/AlignmentMaskAnalysis.cpp',
-    'jit/BacktrackingAllocator.cpp',
-    'jit/Bailouts.cpp',
-    'jit/BaselineBailouts.cpp',
-    'jit/BaselineCacheIRCompiler.cpp',
-    'jit/BaselineCompiler.cpp',
-    'jit/BaselineDebugModeOSR.cpp',
-    'jit/BaselineFrame.cpp',
-    'jit/BaselineFrameInfo.cpp',
-    'jit/BaselineIC.cpp',
-    'jit/BaselineInspector.cpp',
-    'jit/BaselineJIT.cpp',
-    'jit/BitSet.cpp',
-    'jit/BytecodeAnalysis.cpp',
-    'jit/CacheIR.cpp',
-    'jit/CacheIRCompiler.cpp',
-    'jit/CacheIRSpewer.cpp',
-    'jit/CodeGenerator.cpp',
-    'jit/CompileWrappers.cpp',
-    'jit/EdgeCaseAnalysis.cpp',
-    'jit/EffectiveAddressAnalysis.cpp',
-    'jit/ExecutableAllocator.cpp',
-    'jit/FoldLinearArithConstants.cpp',
-    'jit/InstructionReordering.cpp',
-    'jit/Ion.cpp',
-    'jit/IonAnalysis.cpp',
-    'jit/IonBuilder.cpp',
-    'jit/IonCacheIRCompiler.cpp',
-    'jit/IonControlFlow.cpp',
-    'jit/IonIC.cpp',
-    'jit/IonOptimizationLevels.cpp',
-    'jit/Jit.cpp',
-    'jit/JitcodeMap.cpp',
-    'jit/JitFrames.cpp',
-    'jit/JitOptions.cpp',
-    'jit/JitSpewer.cpp',
-    'jit/JSJitFrameIter.cpp',
-    'jit/JSONSpewer.cpp',
-    'jit/LICM.cpp',
-    'jit/Linker.cpp',
-    'jit/LIR.cpp',
-    'jit/LoopUnroller.cpp',
-    'jit/Lowering.cpp',
-    'jit/MacroAssembler.cpp',
-    'jit/MCallOptimize.cpp',
-    'jit/MIR.cpp',
-    'jit/MIRGraph.cpp',
-    'jit/MoveResolver.cpp',
-    'jit/OptimizationTracking.cpp',
-    'jit/PerfSpewer.cpp',
-    'jit/ProcessExecutableMemory.cpp',
-    'jit/RangeAnalysis.cpp',
-    'jit/Recover.cpp',
-    'jit/RegisterAllocator.cpp',
-    'jit/RematerializedFrame.cpp',
-    'jit/Safepoints.cpp',
-    'jit/ScalarReplacement.cpp',
-    'jit/shared/Assembler-shared.cpp',
-    'jit/shared/CodeGenerator-shared.cpp',
-    'jit/shared/Disassembler-shared.cpp',
-    'jit/shared/Lowering-shared.cpp',
-    'jit/Sink.cpp',
-    'jit/Snapshots.cpp',
-    'jit/StupidAllocator.cpp',
-    'jit/TypedObjectPrediction.cpp',
-    'jit/TypePolicy.cpp',
-    'jit/ValueNumbering.cpp',
-    'jit/VMFunctions.cpp',
-    'jit/WasmBCE.cpp',
     'jsapi.cpp',
     'jsdate.cpp',
     'jsexn.cpp',
     'jsfriendapi.cpp',
     'jsnum.cpp',
     'perf/jsperf.cpp',
     'proxy/BaseProxyHandler.cpp',
     'proxy/CrossCompartmentWrapper.cpp',
@@ -501,149 +418,16 @@ if CONFIG['MOZ_INSTRUMENTS']:
 
 if CONFIG['ENABLE_TRACE_LOGGING']:
     SOURCES += [
         'vm/TraceLogging.cpp',
         'vm/TraceLoggingGraph.cpp',
         'vm/TraceLoggingTypes.cpp',
     ]
 
-if not CONFIG['ENABLE_ION']:
-    LOpcodesGenerated.inputs += ['jit/none/LIR-none.h']
-    UNIFIED_SOURCES += [
-        'jit/none/Trampoline-none.cpp'
-    ]
-elif CONFIG['JS_CODEGEN_X86'] or CONFIG['JS_CODEGEN_X64']:
-    LOpcodesGenerated.inputs += ['jit/x86-shared/LIR-x86-shared.h']
-    UNIFIED_SOURCES += [
-        'jit/x86-shared/Architecture-x86-shared.cpp',
-        'jit/x86-shared/Assembler-x86-shared.cpp',
-        'jit/x86-shared/AssemblerBuffer-x86-shared.cpp',
-        'jit/x86-shared/CodeGenerator-x86-shared.cpp',
-        'jit/x86-shared/Lowering-x86-shared.cpp',
-        'jit/x86-shared/MacroAssembler-x86-shared-SIMD.cpp',
-        'jit/x86-shared/MacroAssembler-x86-shared.cpp',
-        'jit/x86-shared/MoveEmitter-x86-shared.cpp',
-    ]
-    if CONFIG['JS_CODEGEN_X64']:
-        LOpcodesGenerated.inputs += ['jit/x64/LIR-x64.h']
-        UNIFIED_SOURCES += [
-            'jit/x64/Assembler-x64.cpp',
-            'jit/x64/Bailouts-x64.cpp',
-            'jit/x64/CodeGenerator-x64.cpp',
-            'jit/x64/Lowering-x64.cpp',
-            'jit/x64/MacroAssembler-x64.cpp',
-            'jit/x64/Trampoline-x64.cpp',
-        ]
-    else:
-        LOpcodesGenerated.inputs += ['jit/x86/LIR-x86.h']
-        UNIFIED_SOURCES += [
-            'jit/x86/Assembler-x86.cpp',
-            'jit/x86/Bailouts-x86.cpp',
-            'jit/x86/CodeGenerator-x86.cpp',
-            'jit/x86/Lowering-x86.cpp',
-            'jit/x86/MacroAssembler-x86.cpp',
-            'jit/x86/Trampoline-x86.cpp',
-        ]
-elif CONFIG['JS_CODEGEN_ARM']:
-    LOpcodesGenerated.inputs += ['jit/arm/LIR-arm.h']
-    UNIFIED_SOURCES += [
-        'jit/arm/Architecture-arm.cpp',
-        'jit/arm/Assembler-arm.cpp',
-        'jit/arm/Bailouts-arm.cpp',
-        'jit/arm/CodeGenerator-arm.cpp',
-        'jit/arm/disasm/Constants-arm.cpp',
-        'jit/arm/disasm/Disasm-arm.cpp',
-        'jit/arm/Lowering-arm.cpp',
-        'jit/arm/MacroAssembler-arm.cpp',
-        'jit/arm/MoveEmitter-arm.cpp',
-        'jit/arm/Trampoline-arm.cpp',
-    ]
-    if CONFIG['JS_SIMULATOR_ARM']:
-        UNIFIED_SOURCES += [
-            'jit/arm/Simulator-arm.cpp'
-        ]
-    elif CONFIG['OS_ARCH'] == 'Darwin':
-        SOURCES += [
-            'jit/arm/llvm-compiler-rt/arm/aeabi_idivmod.S',
-            'jit/arm/llvm-compiler-rt/arm/aeabi_uidivmod.S',
-        ]
-elif CONFIG['JS_CODEGEN_ARM64']:
-    LOpcodesGenerated.inputs += ['jit/arm64/LIR-arm64.h']
-    UNIFIED_SOURCES += [
-        'jit/arm64/Architecture-arm64.cpp',
-        'jit/arm64/Assembler-arm64.cpp',
-        'jit/arm64/Bailouts-arm64.cpp',
-        'jit/arm64/CodeGenerator-arm64.cpp',
-        'jit/arm64/Lowering-arm64.cpp',
-        'jit/arm64/MacroAssembler-arm64.cpp',
-        'jit/arm64/MoveEmitter-arm64.cpp',
-        'jit/arm64/Trampoline-arm64.cpp',
-        'jit/arm64/vixl/Assembler-vixl.cpp',
-        'jit/arm64/vixl/Cpu-vixl.cpp',
-        'jit/arm64/vixl/Decoder-vixl.cpp',
-        'jit/arm64/vixl/Disasm-vixl.cpp',
-        'jit/arm64/vixl/Instructions-vixl.cpp',
-        'jit/arm64/vixl/Instrument-vixl.cpp',
-        'jit/arm64/vixl/MacroAssembler-vixl.cpp',
-        'jit/arm64/vixl/MozAssembler-vixl.cpp',
-        'jit/arm64/vixl/MozInstructions-vixl.cpp',
-        'jit/arm64/vixl/Utils-vixl.cpp'
-    ]
-    if CONFIG['JS_SIMULATOR_ARM64']:
-        UNIFIED_SOURCES += [
-            'jit/arm64/vixl/Debugger-vixl.cpp',
-            'jit/arm64/vixl/Logic-vixl.cpp',
-            'jit/arm64/vixl/MozSimulator-vixl.cpp',
-            'jit/arm64/vixl/Simulator-vixl.cpp'
-        ]
-elif CONFIG['JS_CODEGEN_MIPS32'] or CONFIG['JS_CODEGEN_MIPS64']:
-    LOpcodesGenerated.inputs += ['jit/mips-shared/LIR-mips-shared.h']
-    UNIFIED_SOURCES += [
-        'jit/mips-shared/Architecture-mips-shared.cpp',
-        'jit/mips-shared/Assembler-mips-shared.cpp',
-        'jit/mips-shared/Bailouts-mips-shared.cpp',
-        'jit/mips-shared/CodeGenerator-mips-shared.cpp',
-        'jit/mips-shared/Lowering-mips-shared.cpp',
-        'jit/mips-shared/MacroAssembler-mips-shared.cpp',
-        'jit/mips-shared/MoveEmitter-mips-shared.cpp',
-    ]
-    if CONFIG['JS_CODEGEN_MIPS32']:
-        LOpcodesGenerated.inputs += ['jit/mips32/LIR-mips32.h']
-        UNIFIED_SOURCES += [
-            'jit/mips32/Architecture-mips32.cpp',
-            'jit/mips32/Assembler-mips32.cpp',
-            'jit/mips32/Bailouts-mips32.cpp',
-            'jit/mips32/CodeGenerator-mips32.cpp',
-            'jit/mips32/Lowering-mips32.cpp',
-            'jit/mips32/MacroAssembler-mips32.cpp',
-            'jit/mips32/MoveEmitter-mips32.cpp',
-            'jit/mips32/Trampoline-mips32.cpp',
-        ]
-        if CONFIG['JS_SIMULATOR_MIPS32']:
-            UNIFIED_SOURCES += [
-                'jit/mips32/Simulator-mips32.cpp'
-            ]
-    elif CONFIG['JS_CODEGEN_MIPS64']:
-        LOpcodesGenerated.inputs += ['jit/mips64/LIR-mips64.h']
-        UNIFIED_SOURCES += [
-            'jit/mips64/Architecture-mips64.cpp',
-            'jit/mips64/Assembler-mips64.cpp',
-            'jit/mips64/Bailouts-mips64.cpp',
-            'jit/mips64/CodeGenerator-mips64.cpp',
-            'jit/mips64/Lowering-mips64.cpp',
-            'jit/mips64/MacroAssembler-mips64.cpp',
-            'jit/mips64/MoveEmitter-mips64.cpp',
-            'jit/mips64/Trampoline-mips64.cpp',
-        ]
-        if CONFIG['JS_SIMULATOR_MIPS64']:
-            UNIFIED_SOURCES += [
-                'jit/mips64/Simulator-mips64.cpp'
-            ]
-
 if CONFIG['OS_ARCH'] == 'WINNT':
     UNIFIED_SOURCES += [
         'threading/windows/CpuCount.cpp',
         'threading/windows/Thread.cpp',
     ]
 else:
     UNIFIED_SOURCES += [
         'threading/posix/CpuCount.cpp',
@@ -685,16 +469,17 @@ GENERATED_FILES += ['frontend/ReservedWo
 ReservedWordsGenerated = GENERATED_FILES['frontend/ReservedWordsGenerated.h']
 ReservedWordsGenerated.script = 'frontend/GenerateReservedWords.py'
 ReservedWordsGenerated.inputs += [
     'frontend/ReservedWords.h'
 ]
 
 DIRS += [
     'build',
+    'jit',
 ]
 
 FINAL_LIBRARY = 'js'
 
 if CONFIG['ENABLE_WASM_CRANELIFT']:
     DIRS += ['rust']
     UNIFIED_SOURCES += [
         'wasm/WasmCraneliftCompile.cpp',

--- a/js/src/tests/jstests.list
+++ b/js/src/tests/jstests.list
@@ -5,16 +5,26 @@
 skip include test/jstests.list
 
 skip script non262/String/normalize-generateddata-input.js # input data for other test
 
 # Timeouts on arm and cgc builds.
 slow script test262/built-ins/decodeURI/S15.1.3.1_A2.5_T1.js
 slow script test262/built-ins/decodeURIComponent/S15.1.3.2_A2.5_T1.js
 
+# Fields are not fully implemented yet
+# https://bugzilla.mozilla.org/show_bug.cgi?id=1499448
+skip script non262/fields/access.js
+skip script non262/fields/basic.js
+skip script non262/fields/error.js
+skip script non262/fields/field_types.js
+skip script non262/fields/literal.js
+skip script non262/fields/mixed_methods.js
+skip script non262/fields/quirks.js
+
 
 #################################################################
 # Tests disabled due to intentional alternative implementations #
 #################################################################
 
 # Legacy "caller" and "arguments" implemented as accessor properties on Function.prototype.
 skip script test262/built-ins/Function/prototype/restricted-property-arguments.js
 skip script test262/built-ins/Function/prototype/restricted-property-caller.js
@@ -438,29 +448,16 @@ skip script test262/intl402/RelativeTime
 skip script test262/intl402/RelativeTimeFormat/prototype/format/en-us-style-short.js
 skip script test262/intl402/RelativeTimeFormat/prototype/format/pl-pl-style-long.js
 skip script test262/intl402/RelativeTimeFormat/prototype/format/pl-pl-style-narrow.js
 skip script test262/intl402/RelativeTimeFormat/prototype/format/pl-pl-style-short.js
 
 # https://bugzilla.mozilla.org/show_bug.cgi?id=1473588
 skip script test262/intl402/RelativeTimeFormat/prototype/format/unit-plural.js
 
-# https://bugzilla.mozilla.org/show_bug.cgi?id=1499933
-skip script test262/intl402/DateTimeFormat/prototype/resolvedOptions/order.js
-skip script test262/intl402/PluralRules/prototype/resolvedOptions/order.js
-skip script test262/intl402/NumberFormat/prototype/resolvedOptions/order.js
-
-# Fields are not fully implemented yet
-skip script non262/fields/access.js
-skip script non262/fields/basic.js
-skip script non262/fields/error.js
-skip script non262/fields/field_types.js
-skip script non262/fields/literal.js
-skip script non262/fields/mixed_methods.js
-skip script non262/fields/quirks.js
 
 ###########################################################
 # Tests disabled due to issues in test262 importer script #
 ###########################################################
 
 # test262 importer merges all includes in a per directory shell.js file, breaking this harness test case.
 skip script test262/harness/detachArrayBuffer.js
 

--- a/js/src/vm/Time.cpp
+++ b/js/src/vm/Time.cpp
@@ -38,20 +38,36 @@ extern int gettimeofday(struct timeval* 
 #endif
 
 #include <sys/time.h>
 
 #endif /* XP_UNIX */
 
 using mozilla::DebugOnly;
 
-#if defined(XP_UNIX)
+// Forward declare the function
+static int64_t PRMJ_NowImpl();
+
 int64_t
 PRMJ_Now()
 {
+    if (mozilla::TimeStamp::GetFuzzyfoxEnabled()) {
+        return mozilla::TimeStamp::NowFuzzyTime();
+    }
+
+    int64_t now = PRMJ_NowImpl();
+    // We check the FuzzyFox clock in case it was recently disabled, to prevent time
+    // from going backwards.
+    return mozilla::TimeStamp::NowFuzzyTime() > now ? mozilla::TimeStamp::NowFuzzyTime() : now;
+}
+
+#if defined(XP_UNIX)
+static int64_t
+PRMJ_NowImpl()
+{
     struct timeval tv;
 
 #ifdef _SVID_GETTOD   /* Defined only on Solaris, see Solaris <sys/types.h> */
     gettimeofday(&tv);
 #else
     gettimeofday(&tv, 0);
 #endif /* _SVID_GETTOD */
 
@@ -145,24 +161,27 @@ PRMJ_NowShutdown()
     DeleteCriticalSection(&calibration.data_lock);
 }
 
 #define MUTEX_LOCK(m) EnterCriticalSection(m)
 #define MUTEX_UNLOCK(m) LeaveCriticalSection(m)
 #define MUTEX_SETSPINCOUNT(m, c) SetCriticalSectionSpinCount((m),(c))
 
 // Please see bug 363258 for why the win32 timing code is so complex.
-int64_t
-PRMJ_Now()
+static int64_t
+PRMJ_NowImpl()
 {
     if (pGetSystemTimePreciseAsFileTime) {
         // Windows 8 has a new API function that does all the work.
         FILETIME ft;
         pGetSystemTimePreciseAsFileTime(&ft);
-        return int64_t(FileTimeToUnixMicroseconds(ft));
+        int64_t now = int64_t(FileTimeToUnixMicroseconds(ft));
+        // We check the FuzzyFox clock in case it was recently disabled, to prevent time
+        // from going backwards.
+        return mozilla::TimeStamp::NowFuzzyTime() > now ? mozilla::TimeStamp::NowFuzzyTime() : now;
     }
 
     bool calibrated = false;
     bool needsCalibration = !calibration.calibrated;
     double cachedOffset = 0.0;
     while (true) {
         if (needsCalibration) {
             MUTEX_LOCK(&calibration.data_lock);

--- a/layout/base/nsRefreshDriver.cpp
+++ b/layout/base/nsRefreshDriver.cpp
@@ -25,16 +25,17 @@
 // to manually include it
 #include <mmsystem.h>
 #include "WinUtils.h"
 #endif
 
 #include "mozilla/AnimationEventDispatcher.h"
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/AutoRestore.h"
+#include "mozilla/DebugOnly.h"
 #include "mozilla/IntegerRange.h"
 #include "mozilla/dom/FontTableURIProtocolHandler.h"
 #include "nsITimer.h"
 #include "nsLayoutUtils.h"
 #include "nsPresContext.h"
 #include "nsComponentManagerUtils.h"
 #include "mozilla/Logging.h"
 #include "nsAutoPtr.h"
@@ -657,17 +658,20 @@ private:
         MonitorAutoLock lock(mRefreshTickLock);
         aVsyncTimestamp = mRecentVsync;
         mProcessedVsync = true;
       } else {
 
         mLastChildTick = TimeStamp::Now();
         mLastProcessedTickInChildProcess = aVsyncTimestamp;
       }
-      MOZ_ASSERT(aVsyncTimestamp <= TimeStamp::Now());
+
+      // Do not compare timestamps unless they are both canonical or fuzzy
+      DebugOnly<TimeStamp> rightnow = TimeStamp::Now();
+      MOZ_ASSERT_IF((*&rightnow).UsedCanonicalNow() == aVsyncTimestamp.UsedCanonicalNow(), aVsyncTimestamp <= *&rightnow);
 
       // We might have a problem that we call ~VsyncRefreshDriverTimer() before
       // the scheduled TickRefreshDriver() runs. Check mVsyncRefreshDriverTimer
       // before use.
       if (mVsyncRefreshDriverTimer) {
         RefPtr<VsyncRefreshDriverTimer> timer = mVsyncRefreshDriverTimer;
         timer->RunRefreshDrivers(aVsyncTimestamp);
         // Note: mVsyncRefreshDriverTimer might be null now.

--- a/layout/build/nsLayoutStatics.cpp
+++ b/layout/build/nsLayoutStatics.cpp
@@ -97,16 +97,17 @@
 #include "mozilla/dom/CustomElementRegistry.h"
 #include "mozilla/EventDispatcher.h"
 #include "mozilla/IMEStateManager.h"
 #include "mozilla/dom/HTMLVideoElement.h"
 #include "TouchManager.h"
 #include "DecoderDoctorLogger.h"
 #include "MediaDecoder.h"
 #include "mozilla/ClearSiteData.h"
+#include "mozilla/Fuzzyfox.h"
 #include "mozilla/ServoBindings.h"
 #include "mozilla/StaticPresData.h"
 #include "mozilla/dom/WebIDLGlobalNameHash.h"
 #include "mozilla/dom/ipc/IPCBlobInputStreamStorage.h"
 #include "mozilla/dom/U2FTokenManager.h"
 #include "mozilla/dom/PointerEventHandler.h"
 #include "mozilla/dom/BlobURLProtocolHandler.h"
 #include "nsThreadManager.h"
@@ -279,16 +280,18 @@ nsLayoutStatics::Initialize()
   if (XRE_IsParentProcess()) {
     // On content process we initialize DOMPrefs when PContentChild is fully
     // initialized.
     mozilla::dom::DOMPrefs::Initialize();
   }
 
   nsThreadManager::InitializeShutdownObserver();
 
+  mozilla::Fuzzyfox::Start();
+
   ClearSiteData::Initialize();
 
   return NS_OK;
 }
 
 void
 nsLayoutStatics::Shutdown()
 {

--- a/mozglue/misc/TimeStamp.cpp
+++ b/mozglue/misc/TimeStamp.cpp
@@ -3,16 +3,17 @@
 /* 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/. */
 
 /*
  * Implementation of the OS-independent methods of the TimeStamp class
  */
 
+#include "mozilla/Atomics.h"
 #include "mozilla/TimeStamp.h"
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
 
 namespace mozilla {
 
 /**
@@ -40,16 +41,45 @@ struct TimeStampInitialization
   };
 
   ~TimeStampInitialization()
   {
     TimeStamp::Shutdown();
   };
 };
 
+static bool sFuzzyfoxEnabled;
+
+/* static */ bool
+TimeStamp::GetFuzzyfoxEnabled()
+{
+  return sFuzzyfoxEnabled;
+}
+
+/* static */ void
+TimeStamp::SetFuzzyfoxEnabled(bool aValue)
+{
+  sFuzzyfoxEnabled = aValue;
+}
+
+// These variables store the frozen time (as a TimeStamp) for FuzzyFox that
+// will be reported if FuzzyFox is enabled.
+// We overload the top bit of sCanonicalNow and sCanonicalGTC to
+// indicate if a Timestamp is a fuzzed timestamp (bit set) or not
+// (bit unset).
+#ifdef XP_WIN
+static Atomic<uint64_t> sCanonicalGTC;
+static Atomic<uint64_t> sCanonicalQPC;
+static Atomic<bool> sCanonicalHasQPC;
+#else
+static Atomic<uint64_t> sCanonicalNowTimeStamp;
+#endif
+static Atomic<int64_t> sCanonicalNowTime;
+// This variable stores the frozen time (as ms since the epoch) for FuzzyFox
+// to report if FuzzyFox is enabled.
 static TimeStampInitialization sInitOnce;
 
 MFBT_API TimeStamp
 TimeStamp::ProcessCreation(bool* aIsInconsistent)
 {
   if (aIsInconsistent) {
     *aIsInconsistent = false;
   }
@@ -89,9 +119,56 @@ TimeStamp::ProcessCreation(bool* aIsInco
 }
 
 void
 TimeStamp::RecordProcessRestart()
 {
   sInitOnce.mProcessCreation = TimeStamp();
 }
 
+MFBT_API TimeStamp
+TimeStamp::NowFuzzy(TimeStampValue aValue)
+{
+#ifdef XP_WIN
+  TimeStampValue canonicalNow = TimeStampValue(sCanonicalGTC, sCanonicalQPC, sCanonicalHasQPC, true);
+#else
+  TimeStampValue canonicalNow = TimeStampValue(sCanonicalNowTimeStamp);
+#endif
+
+  if (TimeStamp::GetFuzzyfoxEnabled()) {
+    if(MOZ_LIKELY(!canonicalNow.IsNull())) {
+      return TimeStamp(canonicalNow);
+    }
+  }
+  // When we disable Fuzzyfox, time may goes backwards, so we need to make sure
+  // we don't do that.
+  else if (MOZ_UNLIKELY(canonicalNow > aValue)) {
+    return TimeStamp(canonicalNow);
+  }
+
+  return TimeStamp(aValue);
+}
+
+MFBT_API void
+TimeStamp::UpdateFuzzyTimeStamp(TimeStamp aValue)
+{
+#ifdef XP_WIN
+  sCanonicalGTC = aValue.mValue.mGTC;
+  sCanonicalQPC = aValue.mValue.mQPC;
+  sCanonicalHasQPC = aValue.mValue.mHasQPC;
+#else
+  sCanonicalNowTimeStamp = aValue.mValue.mTimeStamp;
+#endif
+}
+
+MFBT_API int64_t
+TimeStamp::NowFuzzyTime()
+{
+  return sCanonicalNowTime;
+}
+
+MFBT_API void
+TimeStamp::UpdateFuzzyTime(int64_t aValue)
+{
+  sCanonicalNowTime = aValue;
+}
+
 } // namespace mozilla

--- a/mozglue/misc/TimeStamp.h
+++ b/mozglue/misc/TimeStamp.h
@@ -24,17 +24,63 @@ template<typename T> struct ParamTraits;
 // defines TimeStampValue as a complex value keeping both
 // GetTickCount and QueryPerformanceCounter values
 #include "TimeStamp_windows.h"
 #endif
 
 namespace mozilla {
 
 #ifndef XP_WIN
-typedef uint64_t TimeStampValue;
+struct TimeStamp63Bit
+{
+  uint64_t mUsedCanonicalNow : 1;
+  uint64_t mTimeStamp        : 63;
+
+  constexpr TimeStamp63Bit()
+    : mUsedCanonicalNow(0)
+    , mTimeStamp(0) { }
+
+  MOZ_IMPLICIT constexpr TimeStamp63Bit(const uint64_t aValue)
+    : mUsedCanonicalNow(0)
+    , mTimeStamp(aValue) { }
+
+  constexpr TimeStamp63Bit(const bool aUsedCanonicalNow, const int64_t aTimeStamp)
+    : mUsedCanonicalNow(aUsedCanonicalNow ? 1 : 0)
+    , mTimeStamp(aTimeStamp) { }
+
+  bool operator==(const TimeStamp63Bit aOther) const
+  {
+    uint64_t here, there;
+    memcpy(&here, this, sizeof(TimeStamp63Bit));
+    memcpy(&there, &aOther, sizeof(TimeStamp63Bit));
+    return here == there;
+  }
+
+  operator uint64_t () const
+  {
+    return mTimeStamp;
+  }
+
+  bool IsNull() const
+  {
+    return mTimeStamp == 0;
+  }
+
+  bool UsedCanonicalNow() const
+  {
+    return mUsedCanonicalNow;
+  }
+
+  void SetCanonicalNow()
+  {
+    mUsedCanonicalNow = 1;
+  }
+};
+
+typedef TimeStamp63Bit TimeStampValue;
 #endif
 
 class TimeStamp;
 
 /**
  * Platform-specific implementation details of BaseTimeDuration.
  */
 class BaseTimeDurationPlatformUtils
@@ -408,17 +454,17 @@ typedef BaseTimeDuration<TimeDurationVal
  * unless there is a specific reason not to do so.
  */
 class TimeStamp
 {
 public:
   /**
    * Initialize to the "null" moment
    */
-  constexpr TimeStamp() : mValue(0) {}
+  constexpr TimeStamp() : mValue() {}
   // Default copy-constructor and assignment are OK
 
   /**
    * The system timestamps are the same as the TimeStamp
    * retrieved by mozilla::TimeStamp. Since we need this for
    * vsync timestamps, we enable the creation of mozilla::TimeStamps
    * on platforms that support vsync aligned refresh drivers / compositors
    * Verified true as of Jan 31, 2015: B2G and OS X
@@ -429,50 +475,59 @@ public:
    * compositors.
    * UNTESTED ON OTHER PLATFORMS
    */
 #if defined(XP_DARWIN) || defined(MOZ_WIDGET_ANDROID) || defined(MOZ_WIDGET_GTK)
   static TimeStamp FromSystemTime(int64_t aSystemTime)
   {
     static_assert(sizeof(aSystemTime) == sizeof(TimeStampValue),
                   "System timestamp should be same units as TimeStampValue");
-    return TimeStamp(aSystemTime);
+    return TimeStamp(TimeStampValue(false, aSystemTime));
   }
 #endif
 
   /**
    * Return true if this is the "null" moment
    */
-  bool IsNull() const { return mValue == 0; }
+  bool IsNull() const { return mValue.IsNull(); }
 
   /**
    * Return true if this is not the "null" moment, may be used in tests, e.g.:
    * |if (timestamp) { ... }|
    */
   explicit operator bool() const
   {
-    return mValue != 0;
+    return !IsNull();
   }
 
+  bool UsedCanonicalNow() const
+  {
+    return mValue.UsedCanonicalNow();
+  }
+  static MFBT_API bool GetFuzzyfoxEnabled();
+  static MFBT_API void SetFuzzyfoxEnabled(bool aValue);
+
   /**
    * Return a timestamp reflecting the current elapsed system time. This
    * is monotonically increasing (i.e., does not decrease) over the
    * lifetime of this process' XPCOM session.
    *
    * Now() is trying to ensure the best possible precision on each platform,
    * at least one millisecond.
    *
    * NowLoRes() has been introduced to workaround performance problems of
    * QueryPerformanceCounter on the Windows platform.  NowLoRes() is giving
    * lower precision, usually 15.6 ms, but with very good performance benefit.
    * Use it for measurements of longer times, like >200ms timeouts.
    */
   static TimeStamp Now() { return Now(true); }
   static TimeStamp NowLoRes() { return Now(false); }
+  static TimeStamp NowUnfuzzed() { return NowUnfuzzed(true); }
 
+  static MFBT_API int64_t NowFuzzyTime();
   /**
    * Return a timestamp representing the time when the current process was
    * created which will be comparable with other timestamps taken with this
    * class. If the actual process creation time is detected to be inconsistent
    * the @a aIsInconsistent parameter will be set to true, the returned
    * timestamp however will still be valid though inaccurate.
    *
    * @param aIsInconsistent If non-null, set to true if an inconsistency was
@@ -526,30 +581,36 @@ public:
   TimeStamp& operator+=(const TimeDuration& aOther)
   {
     MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
     TimeStampValue value = mValue + aOther.mValue;
     // Check for underflow.
     // (We don't check for overflow because it's not obvious what the error
     //  behavior should be in that case.)
     if (aOther.mValue < 0 && value > mValue) {
-      value = 0;
+      value = TimeStampValue();
+    }
+    if (mValue.UsedCanonicalNow()) {
+      value.SetCanonicalNow();
     }
     mValue = value;
     return *this;
   }
   TimeStamp& operator-=(const TimeDuration& aOther)
   {
     MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
     TimeStampValue value = mValue - aOther.mValue;
     // Check for underflow.
     // (We don't check for overflow because it's not obvious what the error
     //  behavior should be in that case.)
     if (aOther.mValue > 0 && value > mValue) {
-      value = 0;
+      value = TimeStampValue();
+    }
+    if (mValue.UsedCanonicalNow()) {
+      value.SetCanonicalNow();
     }
     mValue = value;
     return *this;
   }
 
   bool operator<(const TimeStamp& aOther) const
   {
     MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
@@ -593,16 +654,21 @@ public:
   static MFBT_API void Shutdown();
 
 private:
   friend struct IPC::ParamTraits<mozilla::TimeStamp>;
 
   MOZ_IMPLICIT TimeStamp(TimeStampValue aValue) : mValue(aValue) {}
 
   static MFBT_API TimeStamp Now(bool aHighResolution);
+  static MFBT_API TimeStamp NowUnfuzzed(bool aHighResolution);
+  static MFBT_API TimeStamp NowFuzzy(TimeStampValue aValue);
+
+  static MFBT_API void UpdateFuzzyTime(int64_t aValue);
+  static MFBT_API void UpdateFuzzyTimeStamp(TimeStamp aValue);
 
   /**
    * Computes the uptime of the current process in microseconds. The result
    * is platform-dependent and needs to be checked against existing timestamps
    * for consistency.
    *
    * @returns The number of microseconds since the calling process was started
    *          or 0 if an error was encountered while computing the uptime
@@ -618,13 +684,15 @@ private:
    *
    * PR_INTERVAL_MAX is set at 100,000 ticks per second. So the minimum
    * time to wrap around is about 2^64/100000 seconds, i.e. about
    * 5,849,424 years.
    *
    * When using a system clock, a value is system dependent.
    */
   TimeStampValue mValue;
+
+  friend class Fuzzyfox;
 };
 
 } // namespace mozilla
 
 #endif /* mozilla_TimeStamp_h */

--- a/mozglue/misc/TimeStamp_darwin.cpp
+++ b/mozglue/misc/TimeStamp_darwin.cpp
@@ -154,22 +154,27 @@ TimeStamp::Startup()
 void
 TimeStamp::Shutdown()
 {
 }
 
 TimeStamp
 TimeStamp::Now(bool aHighResolution)
 {
-  return TimeStamp(ClockTime());
+  return TimeStamp::NowFuzzy(TimeStampValue(false, ClockTime()));
+}
+
+TimeStamp
+TimeStamp::NowUnfuzzed(bool aHighResolution)
+{
+  return TimeStamp(TimeStampValue(false, ClockTime()));
 }
 
 // Computes and returns the process uptime in microseconds.
 // Returns 0 if an error was encountered.
-
 uint64_t
 TimeStamp::ComputeProcessUptime()
 {
   struct timeval tv;
   int rv = gettimeofday(&tv, nullptr);
 
   if (rv == -1) {
     return 0;

--- a/mozglue/misc/TimeStamp_posix.cpp
+++ b/mozglue/misc/TimeStamp_posix.cpp
@@ -197,17 +197,23 @@ TimeStamp::Startup()
 void
 TimeStamp::Shutdown()
 {
 }
 
 TimeStamp
 TimeStamp::Now(bool aHighResolution)
 {
-  return TimeStamp(ClockTimeNs());
+  return TimeStamp::NowFuzzy(TimeStampValue(false, ClockTimeNs()));
+}
+
+TimeStamp
+TimeStamp::NowUnfuzzed(bool aHighResolution)
+{
+  return TimeStamp(TimeStampValue(false, ClockTimeNs()));
 }
 
 #if defined(XP_LINUX) || defined(ANDROID)
 
 // Calculates the amount of jiffies that have elapsed since boot and up to the
 // starttime value of a specific process as found in its /proc/*/stat file.
 // Returns 0 if an error occurred.