--- a/toolkit/components/formautofill/moz.build
+++ b/toolkit/components/formautofill/moz.build
@@ -8,17 +8,16 @@ BROWSER_CHROME_MANIFESTS += [
     'test/browser/browser.ini',
 ]
 
 MOCHITEST_CHROME_MANIFESTS += [
     'test/chrome/chrome.ini',
 ]
 
 XPCSHELL_TESTS_MANIFESTS += [
-    'test/xpcshell.ini',
     'test/xpcshell/xpcshell.ini',
 ]
 
 XPIDL_SOURCES += [
     'nsIFormAutofillContentService.idl',
 ]
 
 XPIDL_MODULE = 'toolkit_formautofill'

--- a/toolkit/components/formautofill/test/browser/browser.ini
+++ b/toolkit/components/formautofill/test/browser/browser.ini
@@ -1,7 +1,10 @@
 [DEFAULT]
+# The following files starting with ".." are installed in the current folder.
 support-files =
   ../head_common.js
+  ../loader_common.js
   head.js
+  loader.js
 
 [browser_infrastructure.js]
 [browser_ui_requestAutocomplete.js]

--- a/toolkit/components/formautofill/test/browser/head.js
+++ b/toolkit/components/formautofill/test/browser/head.js
@@ -1,39 +1,18 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
 /*
- * This file makes the common testing infrastructure available to the browser
- * tests located in this folder.  This is only used as an infrastructure file,
- * and new common functions should be added to the "head_common.js" file.
+ * Initialization specific to Form Autofill mochitest-browser tests.
  */
 
 "use strict";
 
-let ChromeUtils = {};
-Services.scriptloader.loadSubScript(
-  "chrome://mochikit/content/tests/SimpleTest/ChromeUtils.js", ChromeUtils);
-
-/* --- Adapters for the mochitest-browser-chrome infrastructure --- */
-
-let Output = {
-  print: info,
-};
+// We cannot start initialization from "loader.js" like we do in the xpcshell
+// and mochitest-chrome frameworks, thus we load the script here.
+Services.scriptloader.loadSubScript(getRootDirectory(gTestPath) + "loader.js",
+                                    this);
 
-let Assert = {
-  ok: function (actual) {
-    let stack = Components.stack.caller;
-    ok(actual, "[" + stack.name + " : " + stack.lineNumber + "] " + actual +
-               " == true");
-  },
-  equal: function (actual, expected) {
-    let stack = Components.stack.caller;
-    is(actual, expected, "[" + stack.name + " : " + stack.lineNumber + "] " +
-               actual + " == " + expected);
-  },
-};
-
-/* --- Shared infrastructure --- */
-
-Services.scriptloader.loadSubScript(
-  "chrome://mochitests/content/browser/" +
-  "toolkit/components/formautofill/test/browser/head_common.js", this);
+// The testing framework is fully initialized at this point, you can add
+// mochitest-browser specific test initialization here.  If you need shared
+// functions or initialization that are not specific to mochitest-browser,
+// consider adding them to "head_common.js" in the parent folder instead.

copy from toolkit/components/formautofill/test/browser/head.js
copy to toolkit/components/formautofill/test/browser/loader.js
--- a/toolkit/components/formautofill/test/browser/head.js
+++ b/toolkit/components/formautofill/test/browser/loader.js
@@ -1,39 +1,42 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
 /*
- * This file makes the common testing infrastructure available to the browser
- * tests located in this folder.  This is only used as an infrastructure file,
- * and new common functions should be added to the "head_common.js" file.
+ * Infrastructure for the mochitest-browser tests located in this folder.
+ *
+ * See "loader_common.js" in the parent folder for a general overview.
+ *
+ * Unless you are adding new features to the framework, you shouldn't have to
+ * modify this file.  Use "head_common.js" or "head.js" for shared code.
  */
 
 "use strict";
 
+Services.scriptloader.loadSubScript(getRootDirectory(gTestPath) +
+                                    "loader_common.js", this);
+
 let ChromeUtils = {};
 Services.scriptloader.loadSubScript(
   "chrome://mochikit/content/tests/SimpleTest/ChromeUtils.js", ChromeUtils);
 
-/* --- Adapters for the mochitest-browser-chrome infrastructure --- */
-
+// Define output functions so they look the same across all frameworks.
 let Output = {
   print: info,
 };
 
+// Define assertion functions so they look the same across all frameworks.
 let Assert = {
-  ok: function (actual) {
-    let stack = Components.stack.caller;
-    ok(actual, "[" + stack.name + " : " + stack.lineNumber + "] " + actual +
-               " == true");
-  },
-  equal: function (actual, expected) {
-    let stack = Components.stack.caller;
-    is(actual, expected, "[" + stack.name + " : " + stack.lineNumber + "] " +
-               actual + " == " + expected);
-  },
+  ok: _mochitestAssert.ok,
+  equal: _mochitestAssert.equal,
 };
 
-/* --- Shared infrastructure --- */
+// Define task registration functions, see description in "loader_common.js".
+let add_task_in_parent_process = add_task;
+let add_task_in_child_process = function () {};
+let add_task_in_both_processes = add_task;
 
-Services.scriptloader.loadSubScript(
-  "chrome://mochitests/content/browser/" +
-  "toolkit/components/formautofill/test/browser/head_common.js", this);
+Services.scriptloader.loadSubScript(getRootDirectory(gTestPath) +
+                                    "head_common.js", this);
+
+// Reminder: unless you are adding new features to the framework, you shouldn't
+// have to modify this file.  Use "head_common.js" or "head.js" for shared code.

--- a/toolkit/components/formautofill/test/chrome/chrome.ini
+++ b/toolkit/components/formautofill/test/chrome/chrome.ini
@@ -1,7 +1,17 @@
 [DEFAULT]
+# The following files starting with ".." are installed in the current folder.
 support-files =
   ../head_common.js
+  ../loader_common.js
   head.js
+  test_infrastructure.js
+  test_requestAutocomplete_cancel.js
+  loader_parent.js
+  loader.js
+
+# For each test defined below, the associated JavaScript file must be declared
+# in the list above.  This is required because a "support-files" declaration on
+# the individual test would override the global list instead of adding entries.
 
 [test_infrastructure.html]
 [test_requestAutocomplete_cancel.html]

--- a/toolkit/components/formautofill/test/chrome/head.js
+++ b/toolkit/components/formautofill/test/chrome/head.js
@@ -1,71 +1,15 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
 /*
- * This file makes the common testing infrastructure available to the chrome
- * tests located in this folder.  This is only used as an infrastructure file,
- * and new common functions should be added to the "head_common.js" file.
+ * Initialization specific to Form Autofill mochitest-chrome tests.
+ *
+ * This file is loaded by "loader.js".
  */
 
 "use strict";
 
-const { classes: Cc, interfaces: Ci, utils: Cu, results: Cr } = Components;
-
-Cu.import("resource://gre/modules/XPCOMUtils.jsm", this);
-Cu.import("resource://gre/modules/Services.jsm", this);
-
-Services.scriptloader.loadSubScript(
-  "chrome://mochikit/content/tests/SimpleTest/SimpleTest.js", this);
-
-let ChromeUtils = {};
-Services.scriptloader.loadSubScript(
-  "chrome://mochikit/content/tests/SimpleTest/ChromeUtils.js", ChromeUtils);
-
-/* --- Adapters for the mochitest-chrome infrastructure --- */
-
-let Output = {
-  print: info,
-};
-
-let Assert = {
-  ok: function (actual) {
-    let stack = Components.stack.caller;
-    ok(actual, "[" + stack.name + " : " + stack.lineNumber + "] " + actual +
-               " == true");
-  },
-  equal: function (actual, expected) {
-    let stack = Components.stack.caller;
-    is(actual, expected, "[" + stack.name + " : " + stack.lineNumber + "] " +
-               actual + " == " + expected);
-  },
-};
-
-let executeSoon = SimpleTest.executeSoon;
-
-let gTestTasks = [];
-let add_task = taskFn => gTestTasks.push(taskFn);
-
-SimpleTest.waitForExplicitFinish();
-
-window.addEventListener("load", function onLoad() {
-  window.removeEventListener("load", onLoad);
-
-  Task.spawn(function* () {
-    try {
-      for (let taskFn of gTestTasks) {
-        info("Running " + taskFn.name);
-        yield Task.spawn(taskFn);
-      }
-    } catch (ex) {
-      ok(false, ex);
-    }
-
-    SimpleTest.finish();
-  });
-});
-
-/* --- Shared infrastructure --- */
-
-let headUrl = "chrome://mochitests/content/chrome/" +
-              "toolkit/components/formautofill/test/chrome/head_common.js";
-Services.scriptloader.loadSubScript(headUrl, this);
+// The testing framework is fully initialized at this point, you can add
+// mochitest-chrome specific test initialization here.  If you need shared
+// functions or initialization that are not specific to mochitest-chrome,
+// consider adding them to "head_common.js" in the parent folder instead.

copy from toolkit/components/formautofill/test/chrome/head.js
copy to toolkit/components/formautofill/test/chrome/loader.js
--- a/toolkit/components/formautofill/test/chrome/head.js
+++ b/toolkit/components/formautofill/test/chrome/loader.js
@@ -1,71 +1,120 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
 /*
- * This file makes the common testing infrastructure available to the chrome
- * tests located in this folder.  This is only used as an infrastructure file,
- * and new common functions should be added to the "head_common.js" file.
+ * Infrastructure for the mochitest-chrome tests located in this folder.
+ *
+ * See "loader_common.js" in the parent folder for a general overview.
+ *
+ * Unless you are adding new features to the framework, you shouldn't have to
+ * modify this file.  Use "head_common.js" or "head.js" for shared code.
  */
 
 "use strict";
 
 const { classes: Cc, interfaces: Ci, utils: Cu, results: Cr } = Components;
 
 Cu.import("resource://gre/modules/XPCOMUtils.jsm", this);
 Cu.import("resource://gre/modules/Services.jsm", this);
 
 Services.scriptloader.loadSubScript(
   "chrome://mochikit/content/tests/SimpleTest/SimpleTest.js", this);
 
+let sharedUrl = SimpleTest.getTestFileURL("loader_common.js");
+Services.scriptloader.loadSubScript(sharedUrl, this);
+
 let ChromeUtils = {};
 Services.scriptloader.loadSubScript(
   "chrome://mochikit/content/tests/SimpleTest/ChromeUtils.js", ChromeUtils);
 
-/* --- Adapters for the mochitest-chrome infrastructure --- */
+let parentScript = SpecialPowers.loadChromeScript(
+                                 SimpleTest.getTestFileURL("loader_parent.js"));
+
+// Replace the extension of the loaded HTML file with ".js"
+let testUrl = location.href.replace(/\.\w+$/, ".js");
 
+// Start loading the test script in the parent process.
+let promiseParentInitFinished = new Promise(function (resolve) {
+  parentScript.addMessageListener("finish_load_in_parent", resolve);
+});
+parentScript.sendAsyncMessage("start_load_in_parent", { testUrl: testUrl });
+
+// Define output functions so they look the same across all frameworks.
 let Output = {
   print: info,
 };
 
+// Define assertion functions so they look the same across all frameworks.
 let Assert = {
-  ok: function (actual) {
-    let stack = Components.stack.caller;
-    ok(actual, "[" + stack.name + " : " + stack.lineNumber + "] " + actual +
-               " == true");
-  },
-  equal: function (actual, expected) {
-    let stack = Components.stack.caller;
-    is(actual, expected, "[" + stack.name + " : " + stack.lineNumber + "] " +
-               actual + " == " + expected);
-  },
+  ok: _mochitestAssert.ok,
+  equal: _mochitestAssert.equal,
 };
 
 let executeSoon = SimpleTest.executeSoon;
 
 let gTestTasks = [];
-let add_task = taskFn => gTestTasks.push(taskFn);
 
-SimpleTest.waitForExplicitFinish();
+// Define task registration functions, see description in "loader_common.js".
+function add_task(taskFn) {
+  gTestTasks.push([taskFn, "content", taskFn.name]);
+}
+function add_task_in_parent_process(taskFn, taskIdOverride) {
+  let taskId = taskIdOverride || getTaskId(Components.stack.caller);
+  gTestTasks.push([taskFn, "parent", taskId]);
+};
+function add_task_in_both_processes(taskFn) {
+  // We need to define a task ID based on our direct caller.
+  add_task_in_parent_process(taskFn, getTaskId(Components.stack.caller));
+  add_task(taskFn);
+};
+let add_task_in_child_process = add_task;
 
 window.addEventListener("load", function onLoad() {
   window.removeEventListener("load", onLoad);
 
   Task.spawn(function* () {
     try {
-      for (let taskFn of gTestTasks) {
-        info("Running " + taskFn.name);
-        yield Task.spawn(taskFn);
+      for (let [taskFn, taskType, taskId] of gTestTasks) {
+        if (taskType == "content") {
+          // This is a normal task executed in the current process.
+          info("Running " + taskFn.name);
+          yield Task.spawn(taskFn);
+        } else {
+          // This is a task executed in the parent process.
+          info("Running task in parent process: " + taskFn.name);
+          let promiseFinished = new Promise(function (resolve) {
+            parentScript.addMessageListener("finish_task_" + taskId, resolve);
+          });
+          parentScript.sendAsyncMessage("start_task_" + taskId);
+          yield promiseFinished;
+          info("Finished task in parent process: " + taskFn.name);
+        }
       }
     } catch (ex) {
       ok(false, ex);
     }
 
     SimpleTest.finish();
   });
 });
 
-/* --- Shared infrastructure --- */
+// Wait for the test script to be loaded in the parent process.  This means that
+// test tasks are registered and ready, but have not been executed yet.
+add_task(function* wait_loading_in_parent_process() {
+  yield promiseParentInitFinished;
+});
+
+let headUrl = SimpleTest.getTestFileURL("head_common.js");
+Services.scriptloader.loadSubScript(headUrl, this);
 
-let headUrl = "chrome://mochitests/content/chrome/" +
-              "toolkit/components/formautofill/test/chrome/head_common.js";
-Services.scriptloader.loadSubScript(headUrl, this);
+Output.print("Loading test file: " + testUrl);
+Services.scriptloader.loadSubScript(testUrl, this);
+
+// Register the execution of termination tasks after all other tasks.
+add_task(terminationTaskFn);
+add_task_in_parent_process(terminationTaskFn, terminationTaskFn.name);
+
+SimpleTest.waitForExplicitFinish();
+
+// Reminder: unless you are adding new features to the framework, you shouldn't
+// have to modify this file.  Use "head_common.js" or "head.js" for shared code.

new file mode 100644
--- /dev/null
+++ b/toolkit/components/formautofill/test/chrome/loader_parent.js
@@ -0,0 +1,77 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/*
+ * Infrastructure for the mochitest-chrome tests located in this folder, always
+ * executed in the parent process.
+ *
+ * See "loader_common.js" in the parent folder for a general overview.
+ *
+ * Unless you are adding new features to the framework, you shouldn't have to
+ * modify this file.  Use "head_common.js" or "head.js" for shared code.
+ */
+
+"use strict";
+
+const { classes: Cc, interfaces: Ci, utils: Cu, results: Cr } = Components;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm", this);
+Cu.import("resource://gre/modules/Services.jsm", this);
+
+let sharedUrl = "chrome://mochitests/content/chrome/" +
+                "toolkit/components/formautofill/test/chrome/loader_common.js";
+Services.scriptloader.loadSubScript(sharedUrl, this);
+
+// Define output functions so they look the same across all frameworks.  Since
+// we don't have an output function available here, we report as TEST-PASS.
+let Output = {
+  print: message => assert.ok(true, message),
+};
+
+// Define assertion functions so they look the same across all frameworks.
+let Assert = {
+  ok: assert.ok,
+  equal: assert.equal,
+};
+
+// Define task registration functions, see description in "loader_common.js".
+function add_task_in_parent_process(taskFn, taskIdOverride) {
+  let taskId = taskIdOverride || getTaskId(Components.stack.caller);
+  Output.print("Registering in the parent process: " + taskId);
+  addMessageListener("start_task_" + taskId, function () {
+    Task.spawn(function* () {
+      try {
+        Output.print("Running in the parent process " + taskId);
+        yield Task.spawn(taskFn);
+      } catch (ex) {
+        assert.ok(false, ex);
+      }
+
+      sendAsyncMessage("finish_task_" + taskId, {});
+    });
+  });
+}
+let add_task = function () {};
+let add_task_in_child_process = function () {};
+let add_task_in_both_processes = add_task_in_parent_process;
+
+// We need to wait for the child process to send us the path of the test file
+// to load before we can actually start loading it.
+let context = this;
+addMessageListener("start_load_in_parent", function (message) {
+  Output.print("Starting loading infrastructure in parent process.");
+  let headUrl = "chrome://mochitests/content/chrome/" +
+                "toolkit/components/formautofill/test/chrome/head_common.js";
+  Services.scriptloader.loadSubScript(headUrl, context);
+
+  Services.scriptloader.loadSubScript(message.testUrl, context);
+
+  // Register the execution of termination tasks after all other tasks.
+  add_task_in_parent_process(terminationTaskFn, terminationTaskFn.name);
+
+  Output.print("Finished loading infrastructure in parent process.");
+  sendAsyncMessage("finish_load_in_parent", {});
+});
+
+// Reminder: unless you are adding new features to the framework, you shouldn't
+// have to modify this file.  Use "head_common.js" or "head.js" for shared code.

--- a/toolkit/components/formautofill/test/chrome/test_infrastructure.html
+++ b/toolkit/components/formautofill/test/chrome/test_infrastructure.html
@@ -1,72 +1,8 @@
 <!DOCTYPE html><html><head><meta charset="utf-8"></head><body>
+<script type="application/javascript;version=1.7" src="loader.js"></script>
 <!-- Any copyright is dedicated to the Public Domain.
    - http://creativecommons.org/publicdomain/zero/1.0/ -->
 
 <p id="paragraph">Paragraph contents.</p>
 
-<script type="application/javascript;version=1.7" src="head.js"></script>
-<script type="application/javascript;version=1.7">
-
-/*
- * Tests the local testing infrastructure.
- */
-
-"use strict";
-
-/**
- * Tests the truth assertion function.
- */
-add_task(function* test_assert_truth() {
-  Assert.ok(1 != 2);
-});
-
-/**
- * Tests the equality assertion function.
- */
-add_task(function* test_assert_equality() {
-  Assert.equal(1 + 1, 2);
-});
-
-/**
- * Uses some of the utility functions provided by the framework.
- */
-add_task(function* test_utility_functions() {
-  // The "print" function is useful to log information that is not known before.
-  let randomString = "R" + Math.floor(Math.random() * 10);
-  Output.print("The random contents will be '" + randomString + "'.");
-
-  // Create the text file with the random contents.
-  let path = yield TestUtils.getTempFile("test-infrastructure.txt");
-  yield OS.File.writeAtomic(path, new TextEncoder().encode(randomString));
-
-  // Test a few utility functions.
-  yield TestUtils.waitForTick();
-  yield TestUtils.waitMs(50);
-
-  let promiseMyNotification = TestUtils.waitForNotification("my-topic");
-  Services.obs.notifyObservers(null, "my-topic", "");
-  yield promiseMyNotification;
-
-  // Check the file size.  The file will be deleted automatically later.
-  Assert.equal((yield OS.File.stat(path)).size, randomString.length);
-});
-
-/**
- * This type of test has access to the content declared above.
- */
-add_task(function* test_content() {
-  Assert.equal($("paragraph").innerHTML, "Paragraph contents.");
-
-  let promiseMyEvent = TestUtils.waitForEvent($("paragraph"), "MyEvent");
-
-  let event = document.createEvent("CustomEvent");
-  event.initCustomEvent("MyEvent", true, false, {});
-  $("paragraph").dispatchEvent(event);
-
-  yield promiseMyEvent;
-});
-
-add_task(terminationTaskFn);
-
-</script>
 </body></html>

new file mode 100644
--- /dev/null
+++ b/toolkit/components/formautofill/test/chrome/test_infrastructure.js
@@ -0,0 +1,61 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/*
+ * Tests the local testing infrastructure.
+ */
+
+"use strict";
+
+/**
+ * Tests the truth assertion function.
+ */
+add_task(function* test_assert_truth() {
+  Assert.ok(1 != 2);
+});
+
+/**
+ * Tests the equality assertion function.
+ */
+add_task(function* test_assert_equality() {
+  Assert.equal(1 + 1, 2);
+});
+
+/**
+ * Uses some of the utility functions provided by the framework.
+ */
+add_task(function* test_utility_functions() {
+  // The "print" function is useful to log information that is not known before.
+  let randomString = "R" + Math.floor(Math.random() * 10);
+  Output.print("The random contents will be '" + randomString + "'.");
+
+  // Create the text file with the random contents.
+  let path = yield TestUtils.getTempFile("test-infrastructure.txt");
+  yield OS.File.writeAtomic(path, new TextEncoder().encode(randomString));
+
+  // Test a few utility functions.
+  yield TestUtils.waitForTick();
+  yield TestUtils.waitMs(50);
+
+  let promiseMyNotification = TestUtils.waitForNotification("my-topic");
+  Services.obs.notifyObservers(null, "my-topic", "");
+  yield promiseMyNotification;
+
+  // Check the file size.  The file will be deleted automatically later.
+  Assert.equal((yield OS.File.stat(path)).size, randomString.length);
+});
+
+/**
+ * This type of test has access to the content declared above.
+ */
+add_task(function* test_content() {
+  Assert.equal($("paragraph").innerHTML, "Paragraph contents.");
+
+  let promiseMyEvent = TestUtils.waitForEvent($("paragraph"), "MyEvent");
+
+  let event = document.createEvent("CustomEvent");
+  event.initCustomEvent("MyEvent", true, false, {});
+  $("paragraph").dispatchEvent(event);
+
+  yield promiseMyEvent;
+});

--- a/toolkit/components/formautofill/test/chrome/test_requestAutocomplete_cancel.html
+++ b/toolkit/components/formautofill/test/chrome/test_requestAutocomplete_cancel.html
@@ -1,38 +1,9 @@
-<!DOCTYPE HTML><html><head><meta charset="utf-8"></head><body>
+<!DOCTYPE html><html><head><meta charset="utf-8"></head><body>
+<script type="application/javascript;version=1.7" src="loader.js"></script>
 <!-- Any copyright is dedicated to the Public Domain.
    - http://creativecommons.org/publicdomain/zero/1.0/ -->
 
 <form id="form">
 </form>
 
-<script type="application/javascript;version=1.7" src="head.js"></script>
-<script type="application/javascript;version=1.7">
-
-/*
- * Tests the response sent when requestAutocomplete is canceled by the user.
- */
-
-"use strict";
-
-/**
- * The requestAutocomplete UI will not be displayed during these tests.
- */
-add_task(function* test_initialize() {
-  FormAutofillTest.requestAutocompleteResponse = { canceled: true };
-});
-
-/**
- * Tests the case where the feature is canceled.
- */
-add_task(function* test_cancel() {
-  let promise = TestUtils.waitForEvent($("form"), "autocompleteerror");
-  $("form").requestAutocomplete();
-  let errorEvent = yield promise;
-
-  Assert.equal(errorEvent.reason, "cancel");
-});
-
-add_task(terminationTaskFn);
-
-</script>
 </body></html>

new file mode 100644
--- /dev/null
+++ b/toolkit/components/formautofill/test/chrome/test_requestAutocomplete_cancel.js
@@ -0,0 +1,26 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/*
+ * Tests the response sent when requestAutocomplete is canceled by the user.
+ */
+
+"use strict";
+
+/**
+ * The requestAutocomplete UI will not be displayed during these tests.
+ */
+add_task_in_parent_process(function* test_cancel_init() {
+  FormAutofillTest.requestAutocompleteResponse = { canceled: true };
+});
+
+/**
+ * Tests the case where the feature is canceled.
+ */
+add_task(function* test_cancel() {
+  let promise = TestUtils.waitForEvent($("form"), "autocompleteerror");
+  $("form").requestAutocomplete();
+  let errorEvent = yield promise;
+
+  Assert.equal(errorEvent.reason, "cancel");
+});

--- a/toolkit/components/formautofill/test/head_common.js
+++ b/toolkit/components/formautofill/test/head_common.js
@@ -1,54 +1,37 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
 /*
- * Provides shared infrastructure for the automated tests.
+ * Initialization of Form Autofill tests shared between all frameworks.
+ *
+ * A copy of this file is installed in each of the framework subfolders, this
+ * means it becomes a sibling of the test files in the final layout.  This is
+ * determined by how manifest "support-files" installation works.
  */
 
 "use strict";
 
+// The requestAutocomplete framework is available at this point, you can add
+// mochitest-chrome specific test initialization here.  If you need shared
+// functions or initialization that are not specific to mochitest-chrome,
+// consider adding them to "head_common.js" in the parent folder instead.
+
 XPCOMUtils.defineLazyModuleGetter(this, "DownloadPaths",
                                   "resource://gre/modules/DownloadPaths.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "FileUtils",
                                   "resource://gre/modules/FileUtils.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "FormAutofill",
                                   "resource://gre/modules/FormAutofill.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "NetUtil",
                                   "resource://gre/modules/NetUtil.jsm");
-XPCOMUtils.defineLazyModuleGetter(this, "Promise",
-                                  "resource://gre/modules/Promise.jsm");
-XPCOMUtils.defineLazyModuleGetter(this, "Task",
-                                  "resource://gre/modules/Task.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "OS",
                                   "resource://gre/modules/osfile.jsm");
 
-let gTerminationTasks = [];
-let add_termination_task = taskFn => gTerminationTasks.push(taskFn);
-
-/**
- * None of the testing frameworks support asynchronous termination functions, so
- * this task must be registered later, after the other "add_task" calls.
- *
- * Even xpcshell doesn't support calling "add_task" in the "tail.js" file,
- * because it registers the task but does not wait for its termination,
- * potentially leading to intermittent failures in subsequent tests.
- */
-let terminationTaskFn = function* test_common_terminate() {
-  for (let taskFn of gTerminationTasks) {
-    try {
-      yield Task.spawn(taskFn);
-    } catch (ex) {
-      Output.print(ex);
-      Assert.ok(false);
-    }
-  }
-};
-
 /* --- Global helpers --- */
 
 // Some of these functions are already implemented in other parts of the source
 // tree, see bug 946708 about sharing more code.
 
 let TestUtils = {
   /**
    * Waits for at least one tick of the event loop.  This means that all pending
@@ -222,23 +205,17 @@ let TestData = {
         }],
       }],
     };
   },
 };
 
 /* --- Initialization and termination functions common to all tests --- */
 
-add_task(function* test_common_initialize() {
-  // We must manually enable the feature while testing.
-  Services.prefs.setBoolPref("dom.forms.requestAutocomplete", true);
-  add_termination_task(function* () {
-    Services.prefs.clearUserPref("dom.forms.requestAutocomplete");
-  });
-
+add_task_in_parent_process(function* () {
   // If required, we return a mock response instead of displaying the UI.
   let mockIntegrationFn = base => ({
     createRequestAutocompleteUI: Task.async(function* () {
       // Call the base method to display the UI if override is not requested.
       if (FormAutofillTest.requestAutocompleteResponse === null) {
         return yield base.createRequestAutocompleteUI.apply(this, arguments);
       }
 
@@ -253,8 +230,16 @@ add_task(function* test_common_initializ
     }),
   });
 
   FormAutofill.registerIntegration(mockIntegrationFn);
   add_termination_task(function* () {
     FormAutofill.unregisterIntegration(mockIntegrationFn);
   });
 });
+
+add_task_in_both_processes(function* () {
+  // We must manually enable the feature while testing.
+  Services.prefs.setBoolPref("dom.forms.requestAutocomplete", true);
+  add_termination_task(function* () {
+    Services.prefs.clearUserPref("dom.forms.requestAutocomplete");
+  });
+});

new file mode 100644
--- /dev/null
+++ b/toolkit/components/formautofill/test/loader_common.js
@@ -0,0 +1,120 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/*
+ * Infrastructure common to the test frameworks located in subfolders.
+ *
+ * A copy of this file is installed in each of the framework subfolders, this
+ * means it becomes a sibling of the test files in the final layout.  This is
+ * determined by how manifest "support-files" installation works.
+ *
+ * Unless you are adding new features to the framework, you shouldn't have to
+ * modify this file.  Use "head_common.js" or the "head.js" file of each
+ * framework for shared code.
+ */
+
+"use strict";
+
+/*
+ * --------------------
+ *  FRAMEWORK OVERVIEW
+ * --------------------
+ *
+ * This framework is designed in such a way that test can be written in similar
+ * ways in the xpcshell, mochitest-chrome, and mochitest-browser frameworks,
+ * both when tests are running in the parent process or in a content process.
+ *
+ * There are some basic self-documenting assertion and output functions:
+ *
+ * Assert.ok(actualValue);
+ * Assert.is(actualValue, expectedValue);
+ * Output.print(string);
+ *
+ * Test cases and initialization functions are declared in shared head files
+ * ("head_common.js" and "head.js") as well as individual test files.  When
+ * tests run in an Elecrolysis (e10s) environment, they are executed in both
+ * processes at first.  Normally, at this point only the registration of test
+ * cases happen.  When everything has finished loading, tests are started and
+ * appropriately synchronized between processes.
+ *
+ * Tests can be declared using the add_task syntax:
+ *
+ * add_task(function* test_something () { ... });
+ *   This adds a test either in the parent process or child process:
+ *     - Parent: xpcshell, mochitest-chrome without --e10s, mochitest-browser
+ *     - Child: mochitest-chrome with --e10s
+ *   In the future, these might run in the child process for "xpcshell --e10s".
+ *
+ * add_task_in_parent_process(function* test_something () { ... });
+ *   This test runs in the parent process, but the child process will wait for
+ *   its completion before continuing with the next task.  This wait currently
+ *   happens only in mochitest-chrome with --e10s, in other frameworks that run
+ *   only in the parent process this is the same as a normal add_task.
+ *
+ * add_task_in_child_process(function* test_something () { ... });
+ *   This test runs only in the child process.  This means that the test is not
+ *   run unless this is an e10s test, currently mochitest-chrome with --e10s.
+ *
+ * add_task_in_both_processes(function* test_something () { ... });
+ *   Useful for initialization that must be done both in the parent and the
+ *   child, like setting preferences.
+ *
+ * add_termination_task(function* () { ... });
+ *   Registers a new asynchronous termination task.  This is executed after all
+ *   test cases in the file finished, and always in the same process where the
+ *   termination task is registered.
+ */
+XPCOMUtils.defineLazyModuleGetter(this, "Promise",
+                                  "resource://gre/modules/Promise.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Task",
+                                  "resource://gre/modules/Task.jsm");
+
+let gTerminationTasks = [];
+
+/**
+ * None of the testing frameworks support asynchronous termination functions, so
+ * this task must be registered later, after the other "add_task" calls.
+ *
+ * Even xpcshell doesn't support calling "add_task" in the "tail.js" file,
+ * because it registers the task but does not wait for its termination,
+ * potentially leading to intermittent failures in subsequent tests.
+ */
+function* terminationTaskFn() {
+  for (let taskFn of gTerminationTasks) {
+    try {
+      yield Task.spawn(taskFn);
+    } catch (ex) {
+      Output.print(ex);
+      Assert.ok(false);
+    }
+  }
+};
+
+function add_termination_task(taskFn) {
+  gTerminationTasks.push(taskFn);
+}
+
+/**
+ * Returns a unique identifier used for synchronizing the given test task
+ * between the parent and child processes.
+ */
+function getTaskId(stackFrame) {
+  return stackFrame.filename + ":" + stackFrame.lineNumber;
+}
+
+// This is a shared helper for mochitest-chrome and mochitest-browser.
+let _mochitestAssert = {
+  ok: function (actual) {
+    let stack = Components.stack.caller;
+    ok(actual, "[" + stack.name + " : " + stack.lineNumber + "] " + actual +
+               " == true");
+  },
+  equal: function (actual, expected) {
+    let stack = Components.stack.caller;
+    is(actual, expected, "[" + stack.name + " : " + stack.lineNumber + "] " +
+               actual + " == " + expected);
+  },
+};
+
+// Reminder: unless you are adding new features to the framework, you shouldn't
+// have to modify this file.  Use "head_common.js" or "head.js" for shared code.

deleted file mode 100644
--- a/toolkit/components/formautofill/test/xpcshell.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[DEFAULT]
-support-files = head_common.js

--- a/toolkit/components/formautofill/test/xpcshell/head.js
+++ b/toolkit/components/formautofill/test/xpcshell/head.js
@@ -1,29 +1,15 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
 /*
- * This file makes the common testing infrastructure available to the xpcshell
- * tests located in this folder.  This is only used as an infrastructure file,
- * and new common functions should be added to the "head_common.js" file.
+ * Initialization specific to Form Autofill xpcshell tests.
+ *
+ * This file is loaded by "loader.js".
  */
 
 "use strict";
 
-const { classes: Cc, interfaces: Ci, utils: Cu, results: Cr } = Components;
-
-Cu.import("resource://gre/modules/XPCOMUtils.jsm", this);
-Cu.import("resource://gre/modules/Services.jsm", this);
-
-/* --- Adapters for the xpcshell infrastructure --- */
-
-let Output = {
-  print: do_print,
-};
-
-let executeSoon = do_execute_soon;
-let setTimeout = (fn, delay) => do_timeout(delay, fn);
-
-function run_test() {
-  do_get_profile();
-  run_next_test();
-}
+// The testing framework is fully initialized at this point, you can add
+// xpcshell specific test initialization here.  If you need shared functions or
+// initialization that are not specific to xpcshell, consider adding them to
+// "head_common.js" in the parent folder instead.

copy from toolkit/components/formautofill/test/xpcshell/head.js
copy to toolkit/components/formautofill/test/xpcshell/loader.js
--- a/toolkit/components/formautofill/test/xpcshell/head.js
+++ b/toolkit/components/formautofill/test/xpcshell/loader.js
@@ -1,29 +1,46 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
 /*
- * This file makes the common testing infrastructure available to the xpcshell
- * tests located in this folder.  This is only used as an infrastructure file,
- * and new common functions should be added to the "head_common.js" file.
+ * Infrastructure for the xpcshell tests located in this folder.
+ *
+ * See "loader_common.js" in the parent folder for a general overview.
+ *
+ * Unless you are adding new features to the framework, you shouldn't have to
+ * modify this file.  Use "head_common.js" or "head.js" for shared code.
  */
 
 "use strict";
 
 const { classes: Cc, interfaces: Ci, utils: Cu, results: Cr } = Components;
 
 Cu.import("resource://gre/modules/XPCOMUtils.jsm", this);
 Cu.import("resource://gre/modules/Services.jsm", this);
 
-/* --- Adapters for the xpcshell infrastructure --- */
+Services.scriptloader.loadSubScript(
+  Services.io.newFileURI(do_get_file("loader_common.js")).spec, this);
 
+// Define output functions so they look the same across all frameworks.
 let Output = {
   print: do_print,
 };
 
 let executeSoon = do_execute_soon;
 let setTimeout = (fn, delay) => do_timeout(delay, fn);
 
+// Define task registration functions, see description in "loader_common.js".
+let add_task_in_parent_process = add_task;
+let add_task_in_child_process = function () {};
+let add_task_in_both_processes = add_task;
+
+Services.scriptloader.loadSubScript(
+  Services.io.newFileURI(do_get_file("head_common.js")).spec, this);
+
+// Tests are always run asynchronously and with the profile loaded.
 function run_test() {
   do_get_profile();
   run_next_test();
 }
+
+// Reminder: unless you are adding new features to the framework, you shouldn't
+// have to modify this file.  Use "head_common.js" or "head.js" for shared code.

--- a/toolkit/components/formautofill/test/xpcshell/test_integration.js
+++ b/toolkit/components/formautofill/test/xpcshell/test_integration.js
@@ -5,17 +5,17 @@
  * Tests overriding the FormAutofillIntegration module functions.
  */
 
 "use strict";
 
 /**
  * The requestAutocomplete UI will not be displayed during these tests.
  */
-add_task(function* test_initialize() {
+add_task_in_parent_process(function* test_initialize() {
   FormAutofillTest.requestAutocompleteResponse = { canceled: true };
 });
 
 /**
  * Registers and unregisters an integration override function.
  */
 add_task(function* test_integration_override() {
   let overrideCalled = false;

--- a/toolkit/components/formautofill/test/xpcshell/xpcshell.ini
+++ b/toolkit/components/formautofill/test/xpcshell/xpcshell.ini
@@ -1,6 +1,11 @@
 [DEFAULT]
-head = head.js ../head_common.js
+head = loader.js head.js
 tail =
+# The following files starting with ".." are installed in the current folder.
+# However, they cannot be referenced directly in the "head" directive above.
+support-files =
+  ../head_common.js
+  ../loader_common.js
 
 [test_infrastructure.js]
 [test_integration.js]