Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

19 files changed, 9553 insertions, 0 deletions

diff --git a/testing/mochitest/tests/SimpleTest/AccessibilityUtils.js b/testing/mochitest/tests/SimpleTest/AccessibilityUtils.js
new file mode 100644
index 0000000000..481c6b5d35
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/AccessibilityUtils.js
@@ -0,0 +1,561 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/**
+ * Accessible states used to check node's state from the accessiblity API
+ * perspective.
+ *
+ * Note: if gecko is built with --disable-accessibility, the interfaces
+ * are not defined. This is why we use getters instead to be able to use
+ * these statically.
+ */
+
+this.AccessibilityUtils = (function () {
+  const FORCE_DISABLE_ACCESSIBILITY_PREF = "accessibility.force_disabled";
+
+  // Accessible states.
+  const { STATE_FOCUSABLE, STATE_INVISIBLE, STATE_LINKED, STATE_UNAVAILABLE } =
+    Ci.nsIAccessibleStates;
+
+  // Accessible action for showing long description.
+  const CLICK_ACTION = "click";
+
+  // Roles that are considered focusable with the keyboard.
+  const KEYBOARD_FOCUSABLE_ROLES = new Set([
+    Ci.nsIAccessibleRole.ROLE_BUTTONMENU,
+    Ci.nsIAccessibleRole.ROLE_CHECKBUTTON,
+    Ci.nsIAccessibleRole.ROLE_COMBOBOX,
+    Ci.nsIAccessibleRole.ROLE_EDITCOMBOBOX,
+    Ci.nsIAccessibleRole.ROLE_ENTRY,
+    Ci.nsIAccessibleRole.ROLE_LINK,
+    Ci.nsIAccessibleRole.ROLE_LISTBOX,
+    Ci.nsIAccessibleRole.ROLE_PASSWORD_TEXT,
+    Ci.nsIAccessibleRole.ROLE_PUSHBUTTON,
+    Ci.nsIAccessibleRole.ROLE_RADIOBUTTON,
+    Ci.nsIAccessibleRole.ROLE_SLIDER,
+    Ci.nsIAccessibleRole.ROLE_SPINBUTTON,
+    Ci.nsIAccessibleRole.ROLE_SUMMARY,
+    Ci.nsIAccessibleRole.ROLE_SWITCH,
+    Ci.nsIAccessibleRole.ROLE_TOGGLE_BUTTON,
+  ]);
+
+  // Roles that are user interactive.
+  const INTERACTIVE_ROLES = new Set([
+    ...KEYBOARD_FOCUSABLE_ROLES,
+    Ci.nsIAccessibleRole.ROLE_CHECK_MENU_ITEM,
+    Ci.nsIAccessibleRole.ROLE_CHECK_RICH_OPTION,
+    Ci.nsIAccessibleRole.ROLE_COMBOBOX_OPTION,
+    Ci.nsIAccessibleRole.ROLE_MENUITEM,
+    Ci.nsIAccessibleRole.ROLE_OPTION,
+    Ci.nsIAccessibleRole.ROLE_OUTLINE,
+    Ci.nsIAccessibleRole.ROLE_OUTLINEITEM,
+    Ci.nsIAccessibleRole.ROLE_PAGETAB,
+    Ci.nsIAccessibleRole.ROLE_PARENT_MENUITEM,
+    Ci.nsIAccessibleRole.ROLE_RADIO_MENU_ITEM,
+    Ci.nsIAccessibleRole.ROLE_RICH_OPTION,
+  ]);
+
+  // Roles that are considered interactive when they are focusable.
+  const INTERACTIVE_IF_FOCUSABLE_ROLES = new Set([
+    // If article is focusable, we can assume it is inside a feed.
+    Ci.nsIAccessibleRole.ROLE_ARTICLE,
+    // Column header can be focusable.
+    Ci.nsIAccessibleRole.ROLE_COLUMNHEADER,
+    Ci.nsIAccessibleRole.ROLE_GRID_CELL,
+    Ci.nsIAccessibleRole.ROLE_MENUBAR,
+    Ci.nsIAccessibleRole.ROLE_MENUPOPUP,
+    Ci.nsIAccessibleRole.ROLE_PAGETABLIST,
+    // Row header can be focusable.
+    Ci.nsIAccessibleRole.ROLE_ROWHEADER,
+    Ci.nsIAccessibleRole.ROLE_SCROLLBAR,
+    Ci.nsIAccessibleRole.ROLE_SEPARATOR,
+    Ci.nsIAccessibleRole.ROLE_TOOLBAR,
+  ]);
+
+  // Roles that are considered form controls.
+  const FORM_ROLES = new Set([
+    Ci.nsIAccessibleRole.ROLE_CHECKBUTTON,
+    Ci.nsIAccessibleRole.ROLE_CHECK_RICH_OPTION,
+    Ci.nsIAccessibleRole.ROLE_COMBOBOX,
+    Ci.nsIAccessibleRole.ROLE_EDITCOMBOBOX,
+    Ci.nsIAccessibleRole.ROLE_ENTRY,
+    Ci.nsIAccessibleRole.ROLE_LISTBOX,
+    Ci.nsIAccessibleRole.ROLE_PASSWORD_TEXT,
+    Ci.nsIAccessibleRole.ROLE_PROGRESSBAR,
+    Ci.nsIAccessibleRole.ROLE_RADIOBUTTON,
+    Ci.nsIAccessibleRole.ROLE_SLIDER,
+    Ci.nsIAccessibleRole.ROLE_SPINBUTTON,
+    Ci.nsIAccessibleRole.ROLE_SWITCH,
+  ]);
+
+  const DEFAULT_ENV = Object.freeze({
+    // Checks that accessible object has at least one accessible action.
+    actionCountRule: true,
+    // Checks that accessible object (and its corresponding node) is focusable
+    // (has focusable state and its node's tabindex is not set to -1).
+    focusableRule: true,
+    // Checks that clickable accessible object (and its corresponding node) has
+    // appropriate interactive semantics.
+    ifClickableThenInteractiveRule: true,
+    // Checks that accessible object has a role that is considered to be
+    // interactive.
+    interactiveRule: true,
+    // Checks that accessible object has a non-empty label.
+    labelRule: true,
+    // Checks that a node has a corresponging accessible object.
+    mustHaveAccessibleRule: true,
+    // Checks that accessible object (and its corresponding node) have a non-
+    // negative tabindex. Platform accessibility API still sets focusable state
+    // on tabindex=-1 nodes.
+    nonNegativeTabIndexRule: true,
+  });
+
+  let gA11YChecks = false;
+
+  let gEnv = {
+    ...DEFAULT_ENV,
+  };
+
+  /**
+   * Get role attribute for an accessible object if specified for its
+   * corresponding {@code DOMNode}.
+   *
+   * @param   {nsIAccessible} accessible
+   *          Accessible for which to determine its role attribute value.
+   *
+   * @returns {String}
+   *          Role attribute value if specified.
+   */
+  function getAriaRoles(accessible) {
+    try {
+      return accessible.attributes.getStringProperty("xml-roles");
+    } catch (e) {
+      // No xml-roles. nsPersistentProperties throws if the attribute for a key
+      // is not found.
+    }
+
+    return "";
+  }
+
+  /**
+   * Get related accessible objects that are targets of labelled by relation e.g.
+   * labels.
+   * @param   {nsIAccessible} accessible
+   *          Accessible objects to get labels for.
+   *
+   * @returns {Array}
+   *          A list of accessible objects that are labels for a given accessible.
+   */
+  function getLabels(accessible) {
+    const relation = accessible.getRelationByType(
+      Ci.nsIAccessibleRelation.RELATION_LABELLED_BY
+    );
+    return [...relation.getTargets().enumerate(Ci.nsIAccessible)];
+  }
+
+  /**
+   * Test if an accessible has a {@code hidden} attribute.
+   *
+   * @param  {nsIAccessible} accessible
+   *         Accessible object.
+   *
+   * @return {boolean}
+   *         True if the accessible object has a {@code hidden} attribute, false
+   *         otherwise.
+   */
+  function hasHiddenAttribute(accessible) {
+    let hidden = false;
+    try {
+      hidden = accessible.attributes.getStringProperty("hidden");
+    } catch (e) {}
+    // If the property is missing, error will be thrown
+    return hidden && hidden === "true";
+  }
+
+  /**
+   * Test if an accessible is hidden from the user.
+   *
+   * @param  {nsIAccessible} accessible
+   *         Accessible object.
+   *
+   * @return {boolean}
+   *         True if accessible is hidden from user, false otherwise.
+   */
+  function isHidden(accessible) {
+    if (!accessible) {
+      return true;
+    }
+
+    while (accessible) {
+      if (hasHiddenAttribute(accessible)) {
+        return true;
+      }
+
+      accessible = accessible.parent;
+    }
+
+    return false;
+  }
+
+  /**
+   * Check if an accessible has a given state.
+   *
+   * @param  {nsIAccessible} accessible
+   *         Accessible object to test.
+   * @param  {number} stateToMatch
+   *         State to match.
+   *
+   * @return {boolean}
+   *         True if |accessible| has |stateToMatch|, false otherwise.
+   */
+  function matchState(accessible, stateToMatch) {
+    const state = {};
+    accessible.getState(state, {});
+
+    return !!(state.value & stateToMatch);
+  }
+
+  /**
+   * Determine if accessible is focusable with the keyboard.
+   *
+   * @param   {nsIAccessible} accessible
+   *          Accessible for which to determine if it is keyboard focusable.
+   *
+   * @returns {Boolean}
+   *          True if focusable with the keyboard.
+   */
+  function isKeyboardFocusable(accessible) {
+    // State will be focusable even if the tabindex is negative.
+    return (
+      matchState(accessible, STATE_FOCUSABLE) &&
+      // Platform accessibility will still report STATE_FOCUSABLE even with the
+      // tabindex="-1" so we need to check that it is >= 0 to be considered
+      // keyboard focusable.
+      (!gEnv.nonNegativeTabIndexRule || accessible.DOMNode.tabIndex > -1)
+    );
+  }
+
+  function buildMessage(message, DOMNode) {
+    if (DOMNode) {
+      const { id, tagName, className } = DOMNode;
+      message += `: id: ${id}, tagName: ${tagName}, className: ${className}`;
+    }
+
+    return message;
+  }
+
+  /**
+   * Fail a test with a given message because of an issue with a given
+   * accessible object. This is used for cases where there's an actual
+   * accessibility failure that prevents UI from being accessible to keyboard/AT
+   * users.
+   *
+   * @param {String} message
+   * @param {nsIAccessible} accessible
+   *        Accessible to log along with the failure message.
+   */
+  function a11yFail(message, { DOMNode }) {
+    SpecialPowers.SimpleTest.ok(false, buildMessage(message, DOMNode));
+  }
+
+  /**
+   * Log a todo statement with a given message because of an issue with a given
+   * accessible object. This is used for cases where accessibility best
+   * practices are not followed or for something that is not as severe to be
+   * considered a failure.
+   * @param {String} message
+   * @param {nsIAccessible} accessible
+   *        Accessible to log along with the todo message.
+   */
+  function a11yWarn(message, { DOMNode }) {
+    SpecialPowers.SimpleTest.todo(false, buildMessage(message, DOMNode));
+  }
+
+  /**
+   * Test if the node's unavailable via the accessibility API.
+   *
+   * @param {nsIAccessible} accessible
+   *        Accessible object.
+   */
+  function assertEnabled(accessible) {
+    if (matchState(accessible, STATE_UNAVAILABLE)) {
+      a11yFail(
+        "Node is enabled but disabled via the accessibility API",
+        accessible
+      );
+    }
+  }
+
+  /**
+   * Test if it is possible to focus on a node with the keyboard. This method
+   * also checks for additional keyboard focus issues that might arise.
+   *
+   * @param {nsIAccessible} accessible
+   *        Accessible object for a node.
+   */
+  function assertFocusable(accessible) {
+    if (gEnv.focusableRule && !isKeyboardFocusable(accessible)) {
+      const ariaRoles = getAriaRoles(accessible);
+      // Do not force ARIA combobox or listbox to be focusable.
+      if (!ariaRoles.includes("combobox") && !ariaRoles.includes("listbox")) {
+        a11yFail("Node is not focusable via the accessibility API", accessible);
+      }
+
+      return;
+    }
+
+    if (!INTERACTIVE_IF_FOCUSABLE_ROLES.has(accessible.role)) {
+      // ROLE_TABLE is used for grids too which are considered interactive.
+      if (
+        accessible.role === Ci.nsIAccessibleRole.ROLE_TABLE &&
+        !getAriaRoles(accessible).includes("grid")
+      ) {
+        a11yWarn(
+          "Focusable nodes should have interactive semantics",
+          accessible
+        );
+
+        return;
+      }
+    }
+
+    if (accessible.DOMNode.tabIndex > 0) {
+      a11yWarn("Avoid using tabindex attribute greater than zero", accessible);
+    }
+  }
+
+  /**
+   * Test if it is possible to interact with a node via the accessibility API.
+   *
+   * @param {nsIAccessible} accessible
+   *        Accessible object for a node.
+   */
+  function assertInteractive(accessible) {
+    if (gEnv.actionCountRule && accessible.actionCount === 0) {
+      a11yFail("Node does not support any accessible actions", accessible);
+
+      return;
+    }
+
+    if (gEnv.interactiveRule && !INTERACTIVE_ROLES.has(accessible.role)) {
+      if (
+        // Labels that have a label for relation with their target are clickable.
+        (accessible.role !== Ci.nsIAccessibleRole.ROLE_LABEL ||
+          accessible.getRelationByType(
+            Ci.nsIAccessibleRelation.RELATION_LABEL_FOR
+          ).targetsCount === 0) &&
+        // Images that are inside an anchor (have linked state).
+        (accessible.role !== Ci.nsIAccessibleRole.ROLE_GRAPHIC ||
+          !matchState(accessible, STATE_LINKED))
+      ) {
+        // Look for click action in the list of actions.
+        for (let i = 0; i < accessible.actionCount; i++) {
+          if (
+            gEnv.ifClickableThenInteractiveRule &&
+            accessible.getActionName(i) === CLICK_ACTION
+          ) {
+            a11yFail(
+              "Clickable nodes must have interactive semantics",
+              accessible
+            );
+          }
+        }
+      }
+
+      a11yFail(
+        "Node does not have a correct interactive role and may not be " +
+          "manipulated via the accessibility API",
+        accessible
+      );
+    }
+  }
+
+  /**
+   * Test if the node is labelled appropriately for accessibility API.
+   *
+   * @param {nsIAccessible} accessible
+   *        Accessible object for a node.
+   */
+  function assertLabelled(accessible) {
+    const name = accessible.name && accessible.name.trim();
+    if (gEnv.labelRule && !name) {
+      a11yFail("Interactive elements must be labeled", accessible);
+
+      return;
+    }
+
+    const { DOMNode } = accessible;
+    if (FORM_ROLES.has(accessible.role)) {
+      const labels = getLabels(accessible);
+      const hasNameFromVisibleLabel = labels.some(
+        label => !matchState(label, STATE_INVISIBLE)
+      );
+
+      if (!hasNameFromVisibleLabel) {
+        a11yWarn("Form elements should have a visible text label", accessible);
+      }
+    } else if (
+      accessible.role === Ci.nsIAccessibleRole.ROLE_LINK &&
+      DOMNode.nodeName === "AREA" &&
+      DOMNode.hasAttribute("href")
+    ) {
+      const alt = DOMNode.getAttribute("alt");
+      if (alt && alt.trim() !== name) {
+        a11yFail(
+          "Use alt attribute to label area elements that have the href attribute",
+          accessible
+        );
+      }
+    }
+  }
+
+  /**
+   * Test if the node's visible via accessibility API.
+   *
+   * @param {nsIAccessible} accessible
+   *        Accessible object for a node.
+   */
+  function assertVisible(accessible) {
+    if (isHidden(accessible)) {
+      a11yFail(
+        "Node is not currently visible via the accessibility API and may not " +
+          "be manipulated by it",
+        accessible
+      );
+    }
+  }
+
+  /**
+   * Walk node ancestry and force refresh driver tick in every document.
+   * @param {DOMNode} node
+   *        Node for traversing the ancestry.
+   */
+  function forceRefreshDriverTick(node) {
+    const wins = [];
+    let bc = BrowsingContext.getFromWindow(node.ownerDocument.defaultView); // eslint-disable-line
+    while (bc) {
+      wins.push(bc.associatedWindow);
+      bc = bc.embedderWindowGlobal?.browsingContext;
+    }
+
+    let win = wins.pop();
+    while (win) {
+      // Stop the refresh driver from doing its regular ticks and force two
+      // refresh driver ticks: first to let layout update and notify a11y,  and
+      // the second to let a11y process updates.
+      win.windowUtils.advanceTimeAndRefresh(100);
+      win.windowUtils.advanceTimeAndRefresh(100);
+      // Go back to normal refresh driver ticks.
+      win.windowUtils.restoreNormalRefresh();
+      win = wins.pop();
+    }
+  }
+
+  /**
+   * Get an accessible object for a node.
+   * Note: this method will not resolve if accessible object does not become
+   * available for a given node.
+   *
+   * @param  {DOMNode} node
+   *         Node to get the accessible object for.
+   *
+   * @return {nsIAccessible}
+   *         Accessibility object for a given node.
+   */
+  function getAccessible(node) {
+    const accessibilityService = Cc[
+      "@mozilla.org/accessibilityService;1"
+    ].getService(Ci.nsIAccessibilityService);
+    if (!accessibilityService) {
+      // This is likely a build with --disable-accessibility
+      return null;
+    }
+
+    let acc = accessibilityService.getAccessibleFor(node);
+    if (acc) {
+      return acc;
+    }
+
+    // Force refresh tick throughout document hierarchy
+    forceRefreshDriverTick(node);
+    return accessibilityService.getAccessibleFor(node);
+  }
+
+  function runIfA11YChecks(task) {
+    return (...args) => (gA11YChecks ? task(...args) : null);
+  }
+
+  /**
+   * AccessibilityUtils provides utility methods for retrieving accessible objects
+   * and performing accessibility related checks.
+   * Current methods:
+   *   assertCanBeClicked
+   *   setEnv
+   *   resetEnv
+   *
+   */
+  const AccessibilityUtils = {
+    assertCanBeClicked(node) {
+      const acc = getAccessible(node);
+      if (!acc) {
+        if (gEnv.mustHaveAccessibleRule) {
+          a11yFail("Node is not accessible via accessibility API", {
+            DOMNode: node,
+          });
+        }
+
+        return;
+      }
+
+      assertInteractive(acc);
+      assertFocusable(acc);
+      assertVisible(acc);
+      assertEnabled(acc);
+      assertLabelled(acc);
+    },
+
+    setEnv(env = DEFAULT_ENV) {
+      gEnv = {
+        ...DEFAULT_ENV,
+        ...env,
+      };
+    },
+
+    resetEnv() {
+      gEnv = { ...DEFAULT_ENV };
+    },
+
+    reset(a11yChecks = false) {
+      gA11YChecks = a11yChecks;
+
+      const { Services } = SpecialPowers;
+      // Disable accessibility service if it is running and if a11y checks are
+      // disabled.
+      if (!gA11YChecks && Services.appinfo.accessibilityEnabled) {
+        Services.prefs.setIntPref(FORCE_DISABLE_ACCESSIBILITY_PREF, 1);
+        Services.prefs.clearUserPref(FORCE_DISABLE_ACCESSIBILITY_PREF);
+      }
+
+      // Reset accessibility environment flags that might've been set within the
+      // test.
+      this.resetEnv();
+    },
+  };
+
+  AccessibilityUtils.assertCanBeClicked = runIfA11YChecks(
+    AccessibilityUtils.assertCanBeClicked.bind(AccessibilityUtils)
+  );
+
+  AccessibilityUtils.setEnv = runIfA11YChecks(
+    AccessibilityUtils.setEnv.bind(AccessibilityUtils)
+  );
+
+  AccessibilityUtils.resetEnv = runIfA11YChecks(
+    AccessibilityUtils.resetEnv.bind(AccessibilityUtils)
+  );
+
+  return AccessibilityUtils;
+})();
diff --git a/testing/mochitest/tests/SimpleTest/ChromeTask.js b/testing/mochitest/tests/SimpleTest/ChromeTask.js
new file mode 100644
index 0000000000..289f6f2eb2
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/ChromeTask.js
@@ -0,0 +1,174 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+function ChromeTask_ChromeScript() {
+  /* eslint-env mozilla/chrome-script */
+
+  "use strict";
+
+  const { Assert: AssertCls } = ChromeUtils.importESModule(
+    "resource://testing-common/Assert.sys.mjs"
+  );
+
+  addMessageListener("chrome-task:spawn", async function (aData) {
+    let id = aData.id;
+    let source = aData.runnable || "()=>{}";
+
+    function getStack(aStack) {
+      let frames = [];
+      for (let frame = aStack; frame; frame = frame.caller) {
+        frames.push(frame.filename + ":" + frame.name + ":" + frame.lineNumber);
+      }
+      return frames.join("\n");
+    }
+
+    /* eslint-disable no-unused-vars */
+    var Assert = new AssertCls((err, message, stack) => {
+      sendAsyncMessage("chrome-task:test-result", {
+        id,
+        condition: !err,
+        name: err ? err.message : message,
+        stack: getStack(err ? err.stack : stack),
+      });
+    });
+
+    var ok = Assert.ok.bind(Assert);
+    var is = Assert.equal.bind(Assert);
+    var isnot = Assert.notEqual.bind(Assert);
+
+    function todo(expr, name) {
+      sendAsyncMessage("chrome-task:test-todo", { id, expr, name });
+    }
+
+    function todo_is(a, b, name) {
+      sendAsyncMessage("chrome-task:test-todo_is", { id, a, b, name });
+    }
+
+    function info(name) {
+      sendAsyncMessage("chrome-task:test-info", { id, name });
+    }
+    /* eslint-enable no-unused-vars */
+
+    try {
+      let runnablestr = `
+        (() => {
+          return (${source});
+        })();`;
+
+      // eslint-disable-next-line no-eval
+      let runnable = eval(runnablestr);
+      let result = await runnable.call(this, aData.arg);
+      sendAsyncMessage("chrome-task:complete", {
+        id,
+        result,
+      });
+    } catch (ex) {
+      sendAsyncMessage("chrome-task:complete", {
+        id,
+        error: ex.toString(),
+      });
+    }
+  });
+}
+
+/**
+ * This object provides the public module functions.
+ */
+var ChromeTask = {
+  /**
+   * the ChromeScript if it has already been loaded.
+   */
+  _chromeScript: null,
+
+  /**
+   * Mapping from message id to associated promise.
+   */
+  _promises: new Map(),
+
+  /**
+   * Incrementing integer to generate unique message id.
+   */
+  _messageID: 1,
+
+  /**
+   * Creates and starts a new task in the chrome process.
+   *
+   * @param arg A single serializable argument that will be passed to the
+   *             task when executed on the content process.
+   * @param task
+   *        - A generator or function which will be serialized and sent to
+   *          the remote browser to be executed. Unlike Task.spawn, this
+   *          argument may not be an iterator as it will be serialized and
+   *          sent to the remote browser.
+   * @return A promise object where you can register completion callbacks to be
+   *         called when the task terminates.
+   * @resolves With the final returned value of the task if it executes
+   *           successfully.
+   * @rejects An error message if execution fails.
+   */
+  spawn: function ChromeTask_spawn(arg, task) {
+    // Load the frame script if needed.
+    let handle = ChromeTask._chromeScript;
+    if (!handle) {
+      handle = SpecialPowers.loadChromeScript(ChromeTask_ChromeScript);
+      handle.addMessageListener("chrome-task:complete", ChromeTask.onComplete);
+      handle.addMessageListener("chrome-task:test-result", ChromeTask.onResult);
+      handle.addMessageListener("chrome-task:test-info", ChromeTask.onInfo);
+      handle.addMessageListener("chrome-task:test-todo", ChromeTask.onTodo);
+      handle.addMessageListener(
+        "chrome-task:test-todo_is",
+        ChromeTask.onTodoIs
+      );
+      ChromeTask._chromeScript = handle;
+    }
+
+    let deferred = {};
+    deferred.promise = new Promise((resolve, reject) => {
+      deferred.resolve = resolve;
+      deferred.reject = reject;
+    });
+
+    let id = ChromeTask._messageID++;
+    ChromeTask._promises.set(id, deferred);
+
+    handle.sendAsyncMessage("chrome-task:spawn", {
+      id,
+      runnable: task.toString(),
+      arg,
+    });
+
+    return deferred.promise;
+  },
+
+  onComplete(aData) {
+    let deferred = ChromeTask._promises.get(aData.id);
+    ChromeTask._promises.delete(aData.id);
+
+    if (aData.error) {
+      deferred.reject(aData.error);
+    } else {
+      deferred.resolve(aData.result);
+    }
+  },
+
+  onResult(aData) {
+    SimpleTest.record(aData.condition, aData.name);
+  },
+
+  onInfo(aData) {
+    SimpleTest.info(aData.name);
+  },
+
+  onTodo(aData) {
+    SimpleTest.todo(aData.expr, aData.name);
+  },
+
+  onTodoIs(aData) {
+    SimpleTest.todo_is(aData.a, aData.b, aData.name);
+  },
+};
diff --git a/testing/mochitest/tests/SimpleTest/EventUtils.js b/testing/mochitest/tests/SimpleTest/EventUtils.js
new file mode 100644
index 0000000000..35e4dbb3d0
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/EventUtils.js
@@ -0,0 +1,3739 @@
+/**
+ * EventUtils provides some utility methods for creating and sending DOM events.
+ *
+ *  When adding methods to this file, please add a performance test for it.
+ */
+
+// Certain functions assume this is loaded into browser window scope.
+// This is modifiable because certain chrome tests create their own gBrowser.
+/* global gBrowser:true */
+
+// This file is used both in privileged and unprivileged contexts, so we have to
+// be careful about our access to Components.interfaces. We also want to avoid
+// naming collisions with anything that might be defined in the scope that imports
+// this script.
+//
+// Even if the real |Components| doesn't exist, we might shim in a simple JS
+// placebo for compat. An easy way to differentiate this from the real thing
+// is whether the property is read-only or not.  The real |Components| property
+// is read-only.
+/* global _EU_Ci, _EU_Cc, _EU_Cu, _EU_ChromeUtils, _EU_OS */
+window.__defineGetter__("_EU_Ci", function () {
+  var c = Object.getOwnPropertyDescriptor(window, "Components");
+  return c && c.value && !c.writable ? Ci : SpecialPowers.Ci;
+});
+
+window.__defineGetter__("_EU_Cc", function () {
+  var c = Object.getOwnPropertyDescriptor(window, "Components");
+  return c && c.value && !c.writable ? Cc : SpecialPowers.Cc;
+});
+
+window.__defineGetter__("_EU_Cu", function () {
+  var c = Object.getOwnPropertyDescriptor(window, "Components");
+  return c && c.value && !c.writable ? Cu : SpecialPowers.Cu;
+});
+
+window.__defineGetter__("_EU_ChromeUtils", function () {
+  var c = Object.getOwnPropertyDescriptor(window, "ChromeUtils");
+  return c && c.value && !c.writable ? ChromeUtils : SpecialPowers.ChromeUtils;
+});
+
+window.__defineGetter__("_EU_OS", function () {
+  delete this._EU_OS;
+  try {
+    this._EU_OS = _EU_ChromeUtils.import(
+      "resource://gre/modules/AppConstants.jsm"
+    ).platform;
+  } catch (ex) {
+    this._EU_OS = null;
+  }
+  return this._EU_OS;
+});
+
+function _EU_isMac(aWindow = window) {
+  if (window._EU_OS) {
+    return window._EU_OS == "macosx";
+  }
+  if (aWindow) {
+    try {
+      return aWindow.navigator.platform.indexOf("Mac") > -1;
+    } catch (ex) {}
+  }
+  return navigator.platform.indexOf("Mac") > -1;
+}
+
+function _EU_isWin(aWindow = window) {
+  if (window._EU_OS) {
+    return window._EU_OS == "win";
+  }
+  if (aWindow) {
+    try {
+      return aWindow.navigator.platform.indexOf("Win") > -1;
+    } catch (ex) {}
+  }
+  return navigator.platform.indexOf("Win") > -1;
+}
+
+function _EU_isLinux(aWindow = window) {
+  if (window._EU_OS) {
+    return window._EU_OS == "linux";
+  }
+  if (aWindow) {
+    try {
+      return aWindow.navigator.platform.startsWith("Linux");
+    } catch (ex) {}
+  }
+  return navigator.platform.startsWith("Linux");
+}
+
+function _EU_isAndroid(aWindow = window) {
+  if (window._EU_OS) {
+    return window._EU_OS == "android";
+  }
+  if (aWindow) {
+    try {
+      return aWindow.navigator.userAgent.includes("Android");
+    } catch (ex) {}
+  }
+  return navigator.userAgent.includes("Android");
+}
+
+function _EU_maybeWrap(o) {
+  // We're used in some contexts where there is no SpecialPowers and also in
+  // some where it exists but has no wrap() method.  And this is somewhat
+  // independent of whether window.Components is a thing...
+  var haveWrap = false;
+  try {
+    haveWrap = SpecialPowers.wrap != undefined;
+  } catch (e) {
+    // Just leave it false.
+  }
+  if (!haveWrap) {
+    // Not much we can do here.
+    return o;
+  }
+  var c = Object.getOwnPropertyDescriptor(window, "Components");
+  return c && c.value && !c.writable ? o : SpecialPowers.wrap(o);
+}
+
+function _EU_maybeUnwrap(o) {
+  var c = Object.getOwnPropertyDescriptor(window, "Components");
+  return c && c.value && !c.writable ? o : SpecialPowers.unwrap(o);
+}
+
+function _EU_getPlatform() {
+  if (_EU_isWin()) {
+    return "windows";
+  }
+  if (_EU_isMac()) {
+    return "mac";
+  }
+  if (_EU_isAndroid()) {
+    return "android";
+  }
+  if (_EU_isLinux()) {
+    return "linux";
+  }
+  return "unknown";
+}
+
+/**
+ * promiseElementReadyForUserInput() dispatches mousemove events to aElement
+ * and waits one of them for a while.  Then, returns "resolved" state when it's
+ * successfully received.  Otherwise, if it couldn't receive mousemove event on
+ * it, this throws an exception.  So, aElement must be an element which is
+ * assumed non-collapsed visible element in the window.
+ *
+ * This is useful if you need to synthesize mouse events via the main process
+ * but your test cannot check whether the element is now in APZ to deliver
+ * a user input event.
+ */
+async function promiseElementReadyForUserInput(
+  aElement,
+  aWindow = window,
+  aLogFunc = null
+) {
+  if (typeof aElement == "string") {
+    aElement = aWindow.document.getElementById(aElement);
+  }
+
+  function waitForMouseMoveForHittest() {
+    return new Promise(resolve => {
+      let timeout;
+      const onHit = () => {
+        if (aLogFunc) {
+          aLogFunc("mousemove received");
+        }
+        aWindow.clearInterval(timeout);
+        resolve(true);
+      };
+      aElement.addEventListener("mousemove", onHit, {
+        capture: true,
+        once: true,
+      });
+      timeout = aWindow.setInterval(() => {
+        if (aLogFunc) {
+          aLogFunc("mousemove not received in this 300ms");
+        }
+        aElement.removeEventListener("mousemove", onHit, {
+          capture: true,
+        });
+        resolve(false);
+      }, 300);
+      synthesizeMouseAtCenter(aElement, { type: "mousemove" }, aWindow);
+    });
+  }
+  for (let i = 0; i < 20; i++) {
+    if (await waitForMouseMoveForHittest()) {
+      return Promise.resolve();
+    }
+  }
+  throw new Error("The element or the window did not become interactive");
+}
+
+function getElement(id) {
+  return typeof id == "string" ? document.getElementById(id) : id;
+}
+
+this.$ = this.getElement;
+
+function computeButton(aEvent) {
+  if (typeof aEvent.button != "undefined") {
+    return aEvent.button;
+  }
+  return aEvent.type == "contextmenu" ? 2 : 0;
+}
+
+function computeButtons(aEvent, utils) {
+  if (typeof aEvent.buttons != "undefined") {
+    return aEvent.buttons;
+  }
+
+  if (typeof aEvent.button != "undefined") {
+    return utils.MOUSE_BUTTONS_NOT_SPECIFIED;
+  }
+
+  if (typeof aEvent.type != "undefined" && aEvent.type != "mousedown") {
+    return utils.MOUSE_BUTTONS_NO_BUTTON;
+  }
+
+  return utils.MOUSE_BUTTONS_NOT_SPECIFIED;
+}
+
+/**
+ * Send a mouse event to the node aTarget (aTarget can be an id, or an
+ * actual node) . The "event" passed in to aEvent is just a JavaScript
+ * object with the properties set that the real mouse event object should
+ * have. This includes the type of the mouse event. Pretty much all those
+ * properties are optional.
+ * E.g. to send an click event to the node with id 'node' you might do this:
+ *
+ * ``sendMouseEvent({type:'click'}, 'node');``
+ */
+function sendMouseEvent(aEvent, aTarget, aWindow) {
+  if (
+    ![
+      "click",
+      "contextmenu",
+      "dblclick",
+      "mousedown",
+      "mouseup",
+      "mouseover",
+      "mouseout",
+    ].includes(aEvent.type)
+  ) {
+    throw new Error(
+      "sendMouseEvent doesn't know about event type '" + aEvent.type + "'"
+    );
+  }
+
+  if (!aWindow) {
+    aWindow = window;
+  }
+
+  if (typeof aTarget == "string") {
+    aTarget = aWindow.document.getElementById(aTarget);
+  }
+
+  if (aEvent.type === "click" && this.AccessibilityUtils) {
+    this.AccessibilityUtils.assertCanBeClicked(aTarget);
+  }
+
+  var event = aWindow.document.createEvent("MouseEvent");
+
+  var typeArg = aEvent.type;
+  var canBubbleArg = true;
+  var cancelableArg = true;
+  var viewArg = aWindow;
+  var detailArg =
+    aEvent.detail ||
+    // eslint-disable-next-line no-nested-ternary
+    (aEvent.type == "click" ||
+    aEvent.type == "mousedown" ||
+    aEvent.type == "mouseup"
+      ? 1
+      : aEvent.type == "dblclick"
+      ? 2
+      : 0);
+  var screenXArg = aEvent.screenX || 0;
+  var screenYArg = aEvent.screenY || 0;
+  var clientXArg = aEvent.clientX || 0;
+  var clientYArg = aEvent.clientY || 0;
+  var ctrlKeyArg = aEvent.ctrlKey || false;
+  var altKeyArg = aEvent.altKey || false;
+  var shiftKeyArg = aEvent.shiftKey || false;
+  var metaKeyArg = aEvent.metaKey || false;
+  var buttonArg = computeButton(aEvent);
+  var relatedTargetArg = aEvent.relatedTarget || null;
+
+  event.initMouseEvent(
+    typeArg,
+    canBubbleArg,
+    cancelableArg,
+    viewArg,
+    detailArg,
+    screenXArg,
+    screenYArg,
+    clientXArg,
+    clientYArg,
+    ctrlKeyArg,
+    altKeyArg,
+    shiftKeyArg,
+    metaKeyArg,
+    buttonArg,
+    relatedTargetArg
+  );
+
+  // If documentURIObject exists or `window` is a stub object, we're in
+  // a chrome scope, so don't bother trying to go through SpecialPowers.
+  if (!window.document || window.document.documentURIObject) {
+    return aTarget.dispatchEvent(event);
+  }
+  return SpecialPowers.dispatchEvent(aWindow, aTarget, event);
+}
+
+function isHidden(aElement) {
+  var box = aElement.getBoundingClientRect();
+  return box.width == 0 && box.height == 0;
+}
+
+/**
+ * Send a drag event to the node aTarget (aTarget can be an id, or an
+ * actual node) . The "event" passed in to aEvent is just a JavaScript
+ * object with the properties set that the real drag event object should
+ * have. This includes the type of the drag event.
+ */
+function sendDragEvent(aEvent, aTarget, aWindow = window) {
+  if (
+    ![
+      "drag",
+      "dragstart",
+      "dragend",
+      "dragover",
+      "dragenter",
+      "dragleave",
+      "drop",
+    ].includes(aEvent.type)
+  ) {
+    throw new Error(
+      "sendDragEvent doesn't know about event type '" + aEvent.type + "'"
+    );
+  }
+
+  if (typeof aTarget == "string") {
+    aTarget = aWindow.document.getElementById(aTarget);
+  }
+
+  /*
+   * Drag event cannot be performed if the element is hidden, except 'dragend'
+   * event where the element can becomes hidden after start dragging.
+   */
+  if (aEvent.type != "dragend" && isHidden(aTarget)) {
+    var targetName = aTarget.nodeName;
+    if ("id" in aTarget && aTarget.id) {
+      targetName += "#" + aTarget.id;
+    }
+    throw new Error(`${aEvent.type} event target ${targetName} is hidden`);
+  }
+
+  var event = aWindow.document.createEvent("DragEvent");
+
+  var typeArg = aEvent.type;
+  var canBubbleArg = true;
+  var cancelableArg = true;
+  var viewArg = aWindow;
+  var detailArg = aEvent.detail || 0;
+  var screenXArg = aEvent.screenX || 0;
+  var screenYArg = aEvent.screenY || 0;
+  var clientXArg = aEvent.clientX || 0;
+  var clientYArg = aEvent.clientY || 0;
+  var ctrlKeyArg = aEvent.ctrlKey || false;
+  var altKeyArg = aEvent.altKey || false;
+  var shiftKeyArg = aEvent.shiftKey || false;
+  var metaKeyArg = aEvent.metaKey || false;
+  var buttonArg = computeButton(aEvent);
+  var relatedTargetArg = aEvent.relatedTarget || null;
+  var dataTransfer = aEvent.dataTransfer || null;
+
+  event.initDragEvent(
+    typeArg,
+    canBubbleArg,
+    cancelableArg,
+    viewArg,
+    detailArg,
+    screenXArg,
+    screenYArg,
+    clientXArg,
+    clientYArg,
+    ctrlKeyArg,
+    altKeyArg,
+    shiftKeyArg,
+    metaKeyArg,
+    buttonArg,
+    relatedTargetArg,
+    dataTransfer
+  );
+
+  if (aEvent._domDispatchOnly) {
+    return aTarget.dispatchEvent(event);
+  }
+
+  var utils = _getDOMWindowUtils(aWindow);
+  return utils.dispatchDOMEventViaPresShellForTesting(aTarget, event);
+}
+
+/**
+ * Send the char aChar to the focused element.  This method handles casing of
+ * chars (sends the right charcode, and sends a shift key for uppercase chars).
+ * No other modifiers are handled at this point.
+ *
+ * For now this method only works for ASCII characters and emulates the shift
+ * key state on US keyboard layout.
+ */
+function sendChar(aChar, aWindow) {
+  var hasShift;
+  // Emulate US keyboard layout for the shiftKey state.
+  switch (aChar) {
+    case "!":
+    case "@":
+    case "#":
+    case "$":
+    case "%":
+    case "^":
+    case "&":
+    case "*":
+    case "(":
+    case ")":
+    case "_":
+    case "+":
+    case "{":
+    case "}":
+    case ":":
+    case '"':
+    case "|":
+    case "<":
+    case ">":
+    case "?":
+      hasShift = true;
+      break;
+    default:
+      hasShift =
+        aChar.toLowerCase() != aChar.toUpperCase() &&
+        aChar == aChar.toUpperCase();
+      break;
+  }
+  synthesizeKey(aChar, { shiftKey: hasShift }, aWindow);
+}
+
+/**
+ * Send the string aStr to the focused element.
+ *
+ * For now this method only works for ASCII characters and emulates the shift
+ * key state on US keyboard layout.
+ */
+function sendString(aStr, aWindow) {
+  for (var i = 0; i < aStr.length; ++i) {
+    sendChar(aStr.charAt(i), aWindow);
+  }
+}
+
+/**
+ * Send the non-character key aKey to the focused node.
+ * The name of the key should be the part that comes after ``DOM_VK_`` in the
+ * KeyEvent constant name for this key.
+ * No modifiers are handled at this point.
+ */
+function sendKey(aKey, aWindow) {
+  var keyName = "VK_" + aKey.toUpperCase();
+  synthesizeKey(keyName, { shiftKey: false }, aWindow);
+}
+
+/**
+ * Parse the key modifier flags from aEvent. Used to share code between
+ * synthesizeMouse and synthesizeKey.
+ */
+function _parseModifiers(aEvent, aWindow = window) {
+  var nsIDOMWindowUtils = _EU_Ci.nsIDOMWindowUtils;
+  var mval = 0;
+  if (aEvent.shiftKey) {
+    mval |= nsIDOMWindowUtils.MODIFIER_SHIFT;
+  }
+  if (aEvent.ctrlKey) {
+    mval |= nsIDOMWindowUtils.MODIFIER_CONTROL;
+  }
+  if (aEvent.altKey) {
+    mval |= nsIDOMWindowUtils.MODIFIER_ALT;
+  }
+  if (aEvent.metaKey) {
+    mval |= nsIDOMWindowUtils.MODIFIER_META;
+  }
+  if (aEvent.accelKey) {
+    mval |= _EU_isMac(aWindow)
+      ? nsIDOMWindowUtils.MODIFIER_META
+      : nsIDOMWindowUtils.MODIFIER_CONTROL;
+  }
+  if (aEvent.altGrKey) {
+    mval |= nsIDOMWindowUtils.MODIFIER_ALTGRAPH;
+  }
+  if (aEvent.capsLockKey) {
+    mval |= nsIDOMWindowUtils.MODIFIER_CAPSLOCK;
+  }
+  if (aEvent.fnKey) {
+    mval |= nsIDOMWindowUtils.MODIFIER_FN;
+  }
+  if (aEvent.fnLockKey) {
+    mval |= nsIDOMWindowUtils.MODIFIER_FNLOCK;
+  }
+  if (aEvent.numLockKey) {
+    mval |= nsIDOMWindowUtils.MODIFIER_NUMLOCK;
+  }
+  if (aEvent.scrollLockKey) {
+    mval |= nsIDOMWindowUtils.MODIFIER_SCROLLLOCK;
+  }
+  if (aEvent.symbolKey) {
+    mval |= nsIDOMWindowUtils.MODIFIER_SYMBOL;
+  }
+  if (aEvent.symbolLockKey) {
+    mval |= nsIDOMWindowUtils.MODIFIER_SYMBOLLOCK;
+  }
+  if (aEvent.osKey) {
+    mval |= nsIDOMWindowUtils.MODIFIER_OS;
+  }
+
+  return mval;
+}
+
+/**
+ * Synthesize a mouse event on a target. The actual client point is determined
+ * by taking the aTarget's client box and offseting it by aOffsetX and
+ * aOffsetY. This allows mouse clicks to be simulated by calling this method.
+ *
+ * aEvent is an object which may contain the properties:
+ *   `shiftKey`, `ctrlKey`, `altKey`, `metaKey`, `accessKey`, `clickCount`,
+ *   `button`, `type`.
+ *   For valid `type`s see nsIDOMWindowUtils' `sendMouseEvent`.
+ *
+ * If the type is specified, an mouse event of that type is fired. Otherwise,
+ * a mousedown followed by a mouseup is performed.
+ *
+ * aWindow is optional, and defaults to the current window object.
+ *
+ * Returns whether the event had preventDefault() called on it.
+ */
+function synthesizeMouse(aTarget, aOffsetX, aOffsetY, aEvent, aWindow) {
+  var rect = aTarget.getBoundingClientRect();
+  return synthesizeMouseAtPoint(
+    rect.left + aOffsetX,
+    rect.top + aOffsetY,
+    aEvent,
+    aWindow
+  );
+}
+function synthesizeTouch(aTarget, aOffsetX, aOffsetY, aEvent, aWindow) {
+  var rect = aTarget.getBoundingClientRect();
+  return synthesizeTouchAtPoint(
+    rect.left + aOffsetX,
+    rect.top + aOffsetY,
+    aEvent,
+    aWindow
+  );
+}
+
+/*
+ * Synthesize a mouse event at a particular point in aWindow.
+ *
+ * aEvent is an object which may contain the properties:
+ *   `shiftKey`, `ctrlKey`, `altKey`, `metaKey`, `accessKey`, `clickCount`,
+ *   `button`, `type`.
+ *   For valid `type`s see nsIDOMWindowUtils' `sendMouseEvent`.
+ *
+ * If the type is specified, an mouse event of that type is fired. Otherwise,
+ * a mousedown followed by a mouseup is performed.
+ *
+ * aWindow is optional, and defaults to the current window object.
+ */
+function synthesizeMouseAtPoint(left, top, aEvent, aWindow = window) {
+  var utils = _getDOMWindowUtils(aWindow);
+  var defaultPrevented = false;
+
+  if (utils) {
+    var button = computeButton(aEvent);
+    var clickCount = aEvent.clickCount || 1;
+    var modifiers = _parseModifiers(aEvent, aWindow);
+    var pressure = "pressure" in aEvent ? aEvent.pressure : 0;
+
+    // aWindow might be cross-origin from us.
+    var MouseEvent = _EU_maybeWrap(aWindow).MouseEvent;
+
+    // Default source to mouse.
+    var inputSource =
+      "inputSource" in aEvent
+        ? aEvent.inputSource
+        : MouseEvent.MOZ_SOURCE_MOUSE;
+    // Compute a pointerId if needed.
+    var id;
+    if ("id" in aEvent) {
+      id = aEvent.id;
+    } else {
+      var isFromPen = inputSource === MouseEvent.MOZ_SOURCE_PEN;
+      id = isFromPen
+        ? utils.DEFAULT_PEN_POINTER_ID
+        : utils.DEFAULT_MOUSE_POINTER_ID;
+    }
+
+    var isDOMEventSynthesized =
+      "isSynthesized" in aEvent ? aEvent.isSynthesized : true;
+    var isWidgetEventSynthesized =
+      "isWidgetEventSynthesized" in aEvent
+        ? aEvent.isWidgetEventSynthesized
+        : false;
+    if ("type" in aEvent && aEvent.type) {
+      defaultPrevented = utils.sendMouseEvent(
+        aEvent.type,
+        left,
+        top,
+        button,
+        clickCount,
+        modifiers,
+        false,
+        pressure,
+        inputSource,
+        isDOMEventSynthesized,
+        isWidgetEventSynthesized,
+        computeButtons(aEvent, utils),
+        id
+      );
+    } else {
+      utils.sendMouseEvent(
+        "mousedown",
+        left,
+        top,
+        button,
+        clickCount,
+        modifiers,
+        false,
+        pressure,
+        inputSource,
+        isDOMEventSynthesized,
+        isWidgetEventSynthesized,
+        computeButtons(Object.assign({ type: "mousedown" }, aEvent), utils),
+        id
+      );
+      utils.sendMouseEvent(
+        "mouseup",
+        left,
+        top,
+        button,
+        clickCount,
+        modifiers,
+        false,
+        pressure,
+        inputSource,
+        isDOMEventSynthesized,
+        isWidgetEventSynthesized,
+        computeButtons(Object.assign({ type: "mouseup" }, aEvent), utils),
+        id
+      );
+    }
+  }
+
+  return defaultPrevented;
+}
+
+function synthesizeTouchAtPoint(left, top, aEvent, aWindow = window) {
+  var utils = _getDOMWindowUtils(aWindow);
+  let defaultPrevented = false;
+
+  if (utils) {
+    var id = aEvent.id || utils.DEFAULT_TOUCH_POINTER_ID;
+    var rx = aEvent.rx || 1;
+    var ry = aEvent.ry || 1;
+    var angle = aEvent.angle || 0;
+    var force = aEvent.force || (aEvent.type === "touchend" ? 0 : 1);
+    var tiltX = aEvent.tiltX || 0;
+    var tiltY = aEvent.tiltY || 0;
+    var twist = aEvent.twist || 0;
+    var modifiers = _parseModifiers(aEvent, aWindow);
+
+    if ("type" in aEvent && aEvent.type) {
+      defaultPrevented = utils.sendTouchEvent(
+        aEvent.type,
+        [id],
+        [left],
+        [top],
+        [rx],
+        [ry],
+        [angle],
+        [force],
+        [tiltX],
+        [tiltY],
+        [twist],
+        modifiers
+      );
+    } else {
+      utils.sendTouchEvent(
+        "touchstart",
+        [id],
+        [left],
+        [top],
+        [rx],
+        [ry],
+        [angle],
+        [force],
+        [tiltX],
+        [tiltY],
+        [twist],
+        modifiers
+      );
+      utils.sendTouchEvent(
+        "touchend",
+        [id],
+        [left],
+        [top],
+        [rx],
+        [ry],
+        [angle],
+        [force],
+        [tiltX],
+        [tiltY],
+        [twist],
+        modifiers
+      );
+    }
+  }
+  return defaultPrevented;
+}
+
+// Call synthesizeMouse with coordinates at the center of aTarget.
+function synthesizeMouseAtCenter(aTarget, aEvent, aWindow) {
+  var rect = aTarget.getBoundingClientRect();
+  return synthesizeMouse(
+    aTarget,
+    rect.width / 2,
+    rect.height / 2,
+    aEvent,
+    aWindow
+  );
+}
+function synthesizeTouchAtCenter(aTarget, aEvent, aWindow) {
+  var rect = aTarget.getBoundingClientRect();
+  synthesizeTouchAtPoint(
+    rect.left + rect.width / 2,
+    rect.top + rect.height / 2,
+    aEvent,
+    aWindow
+  );
+}
+
+/**
+ * Synthesize a wheel event without flush layout at a particular point in
+ * aWindow.
+ *
+ * aEvent is an object which may contain the properties:
+ *   shiftKey, ctrlKey, altKey, metaKey, accessKey, deltaX, deltaY, deltaZ,
+ *   deltaMode, lineOrPageDeltaX, lineOrPageDeltaY, isMomentum,
+ *   isNoLineOrPageDelta, isCustomizedByPrefs, expectedOverflowDeltaX,
+ *   expectedOverflowDeltaY
+ *
+ * deltaMode must be defined, others are ok even if undefined.
+ *
+ * expectedOverflowDeltaX and expectedOverflowDeltaY take integer value.  The
+ * value is just checked as 0 or positive or negative.
+ *
+ * aWindow is optional, and defaults to the current window object.
+ */
+function synthesizeWheelAtPoint(aLeft, aTop, aEvent, aWindow = window) {
+  var utils = _getDOMWindowUtils(aWindow);
+  if (!utils) {
+    return;
+  }
+
+  var modifiers = _parseModifiers(aEvent, aWindow);
+  var options = 0;
+  if (aEvent.isNoLineOrPageDelta) {
+    options |= utils.WHEEL_EVENT_CAUSED_BY_NO_LINE_OR_PAGE_DELTA_DEVICE;
+  }
+  if (aEvent.isMomentum) {
+    options |= utils.WHEEL_EVENT_CAUSED_BY_MOMENTUM;
+  }
+  if (aEvent.isCustomizedByPrefs) {
+    options |= utils.WHEEL_EVENT_CUSTOMIZED_BY_USER_PREFS;
+  }
+  if (typeof aEvent.expectedOverflowDeltaX !== "undefined") {
+    if (aEvent.expectedOverflowDeltaX === 0) {
+      options |= utils.WHEEL_EVENT_EXPECTED_OVERFLOW_DELTA_X_ZERO;
+    } else if (aEvent.expectedOverflowDeltaX > 0) {
+      options |= utils.WHEEL_EVENT_EXPECTED_OVERFLOW_DELTA_X_POSITIVE;
+    } else {
+      options |= utils.WHEEL_EVENT_EXPECTED_OVERFLOW_DELTA_X_NEGATIVE;
+    }
+  }
+  if (typeof aEvent.expectedOverflowDeltaY !== "undefined") {
+    if (aEvent.expectedOverflowDeltaY === 0) {
+      options |= utils.WHEEL_EVENT_EXPECTED_OVERFLOW_DELTA_Y_ZERO;
+    } else if (aEvent.expectedOverflowDeltaY > 0) {
+      options |= utils.WHEEL_EVENT_EXPECTED_OVERFLOW_DELTA_Y_POSITIVE;
+    } else {
+      options |= utils.WHEEL_EVENT_EXPECTED_OVERFLOW_DELTA_Y_NEGATIVE;
+    }
+  }
+
+  // Avoid the JS warnings "reference to undefined property"
+  if (!aEvent.deltaX) {
+    aEvent.deltaX = 0;
+  }
+  if (!aEvent.deltaY) {
+    aEvent.deltaY = 0;
+  }
+  if (!aEvent.deltaZ) {
+    aEvent.deltaZ = 0;
+  }
+
+  var lineOrPageDeltaX =
+    // eslint-disable-next-line no-nested-ternary
+    aEvent.lineOrPageDeltaX != null
+      ? aEvent.lineOrPageDeltaX
+      : aEvent.deltaX > 0
+      ? Math.floor(aEvent.deltaX)
+      : Math.ceil(aEvent.deltaX);
+  var lineOrPageDeltaY =
+    // eslint-disable-next-line no-nested-ternary
+    aEvent.lineOrPageDeltaY != null
+      ? aEvent.lineOrPageDeltaY
+      : aEvent.deltaY > 0
+      ? Math.floor(aEvent.deltaY)
+      : Math.ceil(aEvent.deltaY);
+  utils.sendWheelEvent(
+    aLeft,
+    aTop,
+    aEvent.deltaX,
+    aEvent.deltaY,
+    aEvent.deltaZ,
+    aEvent.deltaMode,
+    modifiers,
+    lineOrPageDeltaX,
+    lineOrPageDeltaY,
+    options
+  );
+}
+
+/**
+ * Synthesize a wheel event on a target. The actual client point is determined
+ * by taking the aTarget's client box and offseting it by aOffsetX and
+ * aOffsetY.
+ *
+ * aEvent is an object which may contain the properties:
+ *   shiftKey, ctrlKey, altKey, metaKey, accessKey, deltaX, deltaY, deltaZ,
+ *   deltaMode, lineOrPageDeltaX, lineOrPageDeltaY, isMomentum,
+ *   isNoLineOrPageDelta, isCustomizedByPrefs, expectedOverflowDeltaX,
+ *   expectedOverflowDeltaY
+ *
+ * deltaMode must be defined, others are ok even if undefined.
+ *
+ * expectedOverflowDeltaX and expectedOverflowDeltaY take integer value.  The
+ * value is just checked as 0 or positive or negative.
+ *
+ * aWindow is optional, and defaults to the current window object.
+ */
+function synthesizeWheel(aTarget, aOffsetX, aOffsetY, aEvent, aWindow) {
+  var rect = aTarget.getBoundingClientRect();
+  synthesizeWheelAtPoint(
+    rect.left + aOffsetX,
+    rect.top + aOffsetY,
+    aEvent,
+    aWindow
+  );
+}
+
+const _FlushModes = {
+  FLUSH: 0,
+  NOFLUSH: 1,
+};
+
+function _sendWheelAndPaint(
+  aTarget,
+  aOffsetX,
+  aOffsetY,
+  aEvent,
+  aCallback,
+  aFlushMode = _FlushModes.FLUSH,
+  aWindow = window
+) {
+  var utils = _getDOMWindowUtils(aWindow);
+  if (!utils) {
+    return;
+  }
+
+  if (utils.isMozAfterPaintPending) {
+    // If a paint is pending, then APZ may be waiting for a scroll acknowledgement
+    // from the content thread. If we send a wheel event now, it could be ignored
+    // by APZ (or its scroll offset could be overridden). To avoid problems we
+    // just wait for the paint to complete.
+    aWindow.waitForAllPaintsFlushed(function () {
+      _sendWheelAndPaint(
+        aTarget,
+        aOffsetX,
+        aOffsetY,
+        aEvent,
+        aCallback,
+        aFlushMode,
+        aWindow
+      );
+    });
+    return;
+  }
+
+  var onwheel = function () {
+    SpecialPowers.removeSystemEventListener(window, "wheel", onwheel);
+
+    // Wait one frame since the wheel event has not caused a refresh observer
+    // to be added yet.
+    setTimeout(function () {
+      utils.advanceTimeAndRefresh(1000);
+
+      if (!aCallback) {
+        utils.advanceTimeAndRefresh(0);
+        return;
+      }
+
+      var waitForPaints = function () {
+        SpecialPowers.Services.obs.removeObserver(
+          waitForPaints,
+          "apz-repaints-flushed"
+        );
+        aWindow.waitForAllPaintsFlushed(function () {
+          utils.restoreNormalRefresh();
+          aCallback();
+        });
+      };
+
+      SpecialPowers.Services.obs.addObserver(
+        waitForPaints,
+        "apz-repaints-flushed"
+      );
+      if (!utils.flushApzRepaints(aWindow)) {
+        waitForPaints();
+      }
+    }, 0);
+  };
+
+  // Listen for the system wheel event, because it happens after all of
+  // the other wheel events, including legacy events.
+  SpecialPowers.addSystemEventListener(aWindow, "wheel", onwheel);
+  if (aFlushMode === _FlushModes.FLUSH) {
+    synthesizeWheel(aTarget, aOffsetX, aOffsetY, aEvent, aWindow);
+  } else {
+    synthesizeWheelAtPoint(aOffsetX, aOffsetY, aEvent, aWindow);
+  }
+}
+
+/**
+ * This is a wrapper around synthesizeWheel that waits for the wheel event
+ * to be dispatched and for the subsequent layout/paints to be flushed.
+ *
+ * This requires including paint_listener.js. Tests must call
+ * DOMWindowUtils.restoreNormalRefresh() before finishing, if they use this
+ * function.
+ *
+ * If no callback is provided, the caller is assumed to have its own method of
+ * determining scroll completion and the refresh driver is not automatically
+ * restored.
+ */
+function sendWheelAndPaint(
+  aTarget,
+  aOffsetX,
+  aOffsetY,
+  aEvent,
+  aCallback,
+  aWindow = window
+) {
+  _sendWheelAndPaint(
+    aTarget,
+    aOffsetX,
+    aOffsetY,
+    aEvent,
+    aCallback,
+    _FlushModes.FLUSH,
+    aWindow
+  );
+}
+
+/**
+ * Similar to sendWheelAndPaint but without flushing layout for obtaining
+ * ``aTarget`` position in ``aWindow`` before sending the wheel event.
+ * ``aOffsetX`` and ``aOffsetY`` should be offsets against aWindow.
+ */
+function sendWheelAndPaintNoFlush(
+  aTarget,
+  aOffsetX,
+  aOffsetY,
+  aEvent,
+  aCallback,
+  aWindow = window
+) {
+  _sendWheelAndPaint(
+    aTarget,
+    aOffsetX,
+    aOffsetY,
+    aEvent,
+    aCallback,
+    _FlushModes.NOFLUSH,
+    aWindow
+  );
+}
+
+function synthesizeNativeTapAtCenter(
+  aTarget,
+  aLongTap = false,
+  aCallback = null,
+  aWindow = window
+) {
+  let rect = aTarget.getBoundingClientRect();
+  return synthesizeNativeTap(
+    aTarget,
+    rect.width / 2,
+    rect.height / 2,
+    aLongTap,
+    aCallback,
+    aWindow
+  );
+}
+
+function synthesizeNativeTap(
+  aTarget,
+  aOffsetX,
+  aOffsetY,
+  aLongTap = false,
+  aCallback = null,
+  aWindow = window
+) {
+  let utils = _getDOMWindowUtils(aWindow);
+  if (!utils) {
+    return;
+  }
+
+  let scale = aWindow.devicePixelRatio;
+  let rect = aTarget.getBoundingClientRect();
+  let x = (aWindow.mozInnerScreenX + rect.left + aOffsetX) * scale;
+  let y = (aWindow.mozInnerScreenY + rect.top + aOffsetY) * scale;
+
+  let observer = {
+    observe: (subject, topic, data) => {
+      if (aCallback && topic == "mouseevent") {
+        aCallback(data);
+      }
+    },
+  };
+  utils.sendNativeTouchTap(x, y, aLongTap, observer);
+}
+
+/**
+ * Similar to synthesizeMouse but generates a native widget level event
+ * (so will actually move the "real" mouse cursor etc. Be careful because
+ * this can impact later code as well! (e.g. with hover states etc.)
+ *
+ * @description There are 3 mutually exclusive ways of indicating the location of the
+ * mouse event: set ``atCenter``, or pass ``offsetX`` and ``offsetY``,
+ * or pass ``screenX`` and ``screenY``. Do not attempt to mix these.
+ *
+ * @param {object} aParams
+ * @param {string} aParams.type "click", "mousedown", "mouseup" or "mousemove"
+ * @param {Element} aParams.target Origin of offsetX and offsetY, must be an element
+ * @param {Boolean} [aParams.atCenter]
+ *        Instead of offsetX/Y, synthesize the event at center of `target`.
+ * @param {Number} [aParams.offsetX]
+ *        X offset in `target` (in CSS pixels if `scale` is "screenPixelsPerCSSPixel")
+ * @param {Number} [aParams.offsetY]
+ *        Y offset in `target` (in CSS pixels if `scale` is "screenPixelsPerCSSPixel")
+ * @param {Number} [aParams.screenX]
+ *        X offset in screen (in CSS pixels if `scale` is "screenPixelsPerCSSPixel"),
+ *        Neither offsetX/Y nor atCenter must be set if this is set.
+ * @param {Number} [aParams.screenY]
+ *        Y offset in screen (in CSS pixels if `scale` is "screenPixelsPerCSSPixel"),
+ *        Neither offsetX/Y nor atCenter must be set if this is set.
+ * @param {String} [aParams.scale="screenPixelsPerCSSPixel"]
+ *        If scale is "screenPixelsPerCSSPixel", devicePixelRatio will be used.
+ *        If scale is "inScreenPixels", clientX/Y nor scaleX/Y are not adjusted with screenPixelsPerCSSPixel.
+ * @param {Number} [aParams.button=0]
+ *        Defaults to 0, if "click", "mousedown", "mouseup", set same value as DOM MouseEvent.button
+ * @param {Object} [aParams.modifiers={}]
+ *        Active modifiers, see `_parseNativeModifiers`
+ * @param {Window} [aParams.win=window]
+ *        The window to use its utils. Defaults to the window in which EventUtils.js is running.
+ * @param {Element} [aParams.elementOnWidget=target]
+ *        Defaults to target. If element under the point is in another widget from target's widget,
+ *        e.g., when it's in a XUL <panel>, specify this.
+ */
+function synthesizeNativeMouseEvent(aParams, aCallback = null) {
+  const {
+    type,
+    target,
+    offsetX,
+    offsetY,
+    atCenter,
+    screenX,
+    screenY,
+    scale = "screenPixelsPerCSSPixel",
+    button = 0,
+    modifiers = {},
+    win = window,
+    elementOnWidget = target,
+  } = aParams;
+  if (atCenter) {
+    if (offsetX != undefined || offsetY != undefined) {
+      throw Error(
+        `atCenter is specified, but offsetX (${offsetX}) and/or offsetY (${offsetY}) are also specified`
+      );
+    }
+    if (screenX != undefined || screenY != undefined) {
+      throw Error(
+        `atCenter is specified, but screenX (${screenX}) and/or screenY (${screenY}) are also specified`
+      );
+    }
+    if (!target) {
+      throw Error("atCenter is specified, but target is not specified");
+    }
+  } else if (offsetX != undefined && offsetY != undefined) {
+    if (screenX != undefined || screenY != undefined) {
+      throw Error(
+        `offsetX/Y are specified, but screenX (${screenX}) and/or screenY (${screenY}) are also specified`
+      );
+    }
+    if (!target) {
+      throw Error(
+        "offsetX and offsetY are specified, but target is not specified"
+      );
+    }
+  } else if (screenX != undefined && screenY != undefined) {
+    if (offsetX != undefined || offsetY != undefined) {
+      throw Error(
+        `screenX/Y are specified, but offsetX (${offsetX}) and/or offsetY (${offsetY}) are also specified`
+      );
+    }
+  }
+  const utils = _getDOMWindowUtils(win);
+  if (!utils) {
+    return;
+  }
+
+  const rect = target?.getBoundingClientRect();
+  let resolution = 1.0;
+  try {
+    resolution = _getDOMWindowUtils(win.top).getResolution();
+  } catch (e) {
+    // XXX How to get mobile viewport scale on Fission+xorigin since
+    //     window.top access isn't allowed due to cross-origin?
+  }
+  const scaleValue = (() => {
+    if (scale === "inScreenPixels") {
+      return 1.0;
+    }
+    if (scale === "screenPixelsPerCSSPixel") {
+      return win.devicePixelRatio;
+    }
+    throw Error(`invalid scale value (${scale}) is specified`);
+  })();
+  // XXX mozInnerScreen might be invalid value on mobile viewport (Bug 1701546),
+  //     so use window.top's mozInnerScreen. But this won't work fission+xorigin
+  //     with mobile viewport until mozInnerScreen returns valid value with
+  //     scale.
+  const x = (() => {
+    if (screenX != undefined) {
+      return screenX * scaleValue;
+    }
+    let winInnerOffsetX = win.mozInnerScreenX;
+    try {
+      winInnerOffsetX =
+        win.top.mozInnerScreenX +
+        (win.mozInnerScreenX - win.top.mozInnerScreenX) * resolution;
+    } catch (e) {
+      // XXX fission+xorigin test throws permission denied since win.top is
+      //     cross-origin.
+    }
+    return (
+      (((atCenter ? rect.width / 2 : offsetX) + rect.left) * resolution +
+        winInnerOffsetX) *
+      scaleValue
+    );
+  })();
+  const y = (() => {
+    if (screenY != undefined) {
+      return screenY * scaleValue;
+    }
+    let winInnerOffsetY = win.mozInnerScreenY;
+    try {
+      winInnerOffsetY =
+        win.top.mozInnerScreenY +
+        (win.mozInnerScreenY - win.top.mozInnerScreenY) * resolution;
+    } catch (e) {
+      // XXX fission+xorigin test throws permission denied since win.top is
+      //     cross-origin.
+    }
+    return (
+      (((atCenter ? rect.height / 2 : offsetY) + rect.top) * resolution +
+        winInnerOffsetY) *
+      scaleValue
+    );
+  })();
+  const modifierFlags = _parseNativeModifiers(modifiers);
+
+  const observer = {
+    observe: (subject, topic, data) => {
+      if (aCallback && topic == "mouseevent") {
+        aCallback(data);
+      }
+    },
+  };
+  if (type === "click") {
+    utils.sendNativeMouseEvent(
+      x,
+      y,
+      utils.NATIVE_MOUSE_MESSAGE_BUTTON_DOWN,
+      button,
+      modifierFlags,
+      elementOnWidget,
+      function () {
+        utils.sendNativeMouseEvent(
+          x,
+          y,
+          utils.NATIVE_MOUSE_MESSAGE_BUTTON_UP,
+          button,
+          modifierFlags,
+          elementOnWidget,
+          observer
+        );
+      }
+    );
+    return;
+  }
+  utils.sendNativeMouseEvent(
+    x,
+    y,
+    (() => {
+      switch (type) {
+        case "mousedown":
+          return utils.NATIVE_MOUSE_MESSAGE_BUTTON_DOWN;
+        case "mouseup":
+          return utils.NATIVE_MOUSE_MESSAGE_BUTTON_UP;
+        case "mousemove":
+          return utils.NATIVE_MOUSE_MESSAGE_MOVE;
+        default:
+          throw Error(`Invalid type is specified: ${type}`);
+      }
+    })(),
+    button,
+    modifierFlags,
+    elementOnWidget,
+    observer
+  );
+}
+
+function promiseNativeMouseEvent(aParams) {
+  return new Promise(resolve => synthesizeNativeMouseEvent(aParams, resolve));
+}
+
+function synthesizeNativeMouseEventAndWaitForEvent(aParams, aCallback) {
+  const listener = aParams.eventTargetToListen || aParams.target;
+  const eventType = aParams.eventTypeToWait || aParams.type;
+  listener.addEventListener(eventType, aCallback, {
+    capture: true,
+    once: true,
+  });
+  synthesizeNativeMouseEvent(aParams);
+}
+
+function promiseNativeMouseEventAndWaitForEvent(aParams) {
+  return new Promise(resolve =>
+    synthesizeNativeMouseEventAndWaitForEvent(aParams, resolve)
+  );
+}
+
+/**
+ * This is a wrapper around synthesizeNativeMouseEvent that waits for the mouse
+ * event to be dispatched to the target content.
+ *
+ * This API is supposed to be used in those test cases that synthesize some
+ * input events to chrome process and have some checks in content.
+ */
+function synthesizeAndWaitNativeMouseMove(
+  aTarget,
+  aOffsetX,
+  aOffsetY,
+  aCallback,
+  aWindow = window
+) {
+  let browser = gBrowser.selectedTab.linkedBrowser;
+  let mm = browser.messageManager;
+  let { ContentTask } = _EU_ChromeUtils.importESModule(
+    "resource://testing-common/ContentTask.sys.mjs"
+  );
+
+  let eventRegisteredPromise = new Promise(resolve => {
+    mm.addMessageListener(
+      "Test:MouseMoveRegistered",
+      function processed(message) {
+        mm.removeMessageListener("Test:MouseMoveRegistered", processed);
+        resolve();
+      }
+    );
+  });
+  let eventReceivedPromise = ContentTask.spawn(
+    browser,
+    [aOffsetX, aOffsetY],
+    ([clientX, clientY]) => {
+      return new Promise(resolve => {
+        addEventListener("mousemove", function onMouseMoveEvent(e) {
+          if (e.clientX == clientX && e.clientY == clientY) {
+            removeEventListener("mousemove", onMouseMoveEvent);
+            resolve();
+          }
+        });
+        sendAsyncMessage("Test:MouseMoveRegistered");
+      });
+    }
+  );
+  eventRegisteredPromise.then(() => {
+    synthesizeNativeMouseEvent({
+      type: "mousemove",
+      target: aTarget,
+      offsetX: aOffsetX,
+      offsetY: aOffsetY,
+      win: aWindow,
+    });
+  });
+  return eventReceivedPromise;
+}
+
+/**
+ * Synthesize a key event. It is targeted at whatever would be targeted by an
+ * actual keypress by the user, typically the focused element.
+ *
+ * @param {String} aKey
+ *        Should be either:
+ *
+ *        - key value (recommended).  If you specify a non-printable key name,
+ *          prepend the ``KEY_`` prefix.  Otherwise, specifying a printable key, the
+ *          key value should be specified.
+ *
+ *        - keyCode name starting with ``VK_`` (e.g., ``VK_RETURN``).  This is available
+ *          only for compatibility with legacy API.  Don't use this with new tests.
+ *
+ * @param {Object} [aEvent]
+ *        Optional event object with more specifics about the key event to
+ *        synthesize.
+ * @param {String} [aEvent.code]
+ *        If you don't specify this explicitly, it'll be guessed from aKey
+ *        of US keyboard layout.  Note that this value may be different
+ *        between browsers.  For example, "Insert" is never set only on
+ *        macOS since actual key operation won't cause this code value.
+ *        In such case, the value becomes empty string.
+ *        If you need to emulate non-US keyboard layout or virtual keyboard
+ *        which doesn't emulate hardware key input, you should set this value
+ *        to empty string explicitly.
+ * @param {Number} [aEvent.repeat]
+ *        If you emulate auto-repeat, you should set the count of repeat.
+ *        This method will automatically synthesize keydown (and keypress).
+ * @param {*} aEvent.location
+ *        If you want to specify this, you can specify this explicitly.
+ *        However, if you don't specify this value, it will be computed
+ *        from code value.
+ * @param {String} aEvent.type
+ *        Basically, you shouldn't specify this.  Then, this function will
+ *        synthesize keydown (, keypress) and keyup.
+ *        If keydown is specified, this only fires keydown (and keypress if
+ *        it should be fired).
+ *        If keyup is specified, this only fires keyup.
+ * @param {Number} aEvent.keyCode
+ *        Must be 0 - 255 (0xFF). If this is specified explicitly,
+ *        .keyCode value is initialized with this value.
+ * @param {Window} aWindow
+ *        Is optional and defaults to the current window object.
+ * @param {Function} aCallback
+ *        Is optional and can be used to receive notifications from TIP.
+ *
+ * @description
+ * ``accelKey``, ``altKey``, ``altGraphKey``, ``ctrlKey``, ``capsLockKey``,
+ * ``fnKey``, ``fnLockKey``, ``numLockKey``, ``metaKey``, ``osKey``,
+ * ``scrollLockKey``, ``shiftKey``, ``symbolKey``, ``symbolLockKey``
+ * Basically, you shouldn't use these attributes.  nsITextInputProcessor
+ * manages modifier key state when you synthesize modifier key events.
+ * However, if some of these attributes are true, this function activates
+ * the modifiers only during dispatching the key events.
+ * Note that if some of these values are false, they are ignored (i.e.,
+ * not inactivated with this function).
+ *
+ */
+function synthesizeKey(aKey, aEvent = undefined, aWindow = window, aCallback) {
+  var event = aEvent === undefined || aEvent === null ? {} : aEvent;
+
+  var TIP = _getTIP(aWindow, aCallback);
+  if (!TIP) {
+    return;
+  }
+  var KeyboardEvent = _getKeyboardEvent(aWindow);
+  var modifiers = _emulateToActivateModifiers(TIP, event, aWindow);
+  var keyEventDict = _createKeyboardEventDictionary(aKey, event, TIP, aWindow);
+  var keyEvent = new KeyboardEvent("", keyEventDict.dictionary);
+  var dispatchKeydown =
+    !("type" in event) || event.type === "keydown" || !event.type;
+  var dispatchKeyup =
+    !("type" in event) || event.type === "keyup" || !event.type;
+
+  try {
+    if (dispatchKeydown) {
+      TIP.keydown(keyEvent, keyEventDict.flags);
+      if ("repeat" in event && event.repeat > 1) {
+        keyEventDict.dictionary.repeat = true;
+        var repeatedKeyEvent = new KeyboardEvent("", keyEventDict.dictionary);
+        for (var i = 1; i < event.repeat; i++) {
+          TIP.keydown(repeatedKeyEvent, keyEventDict.flags);
+        }
+      }
+    }
+    if (dispatchKeyup) {
+      TIP.keyup(keyEvent, keyEventDict.flags);
+    }
+  } finally {
+    _emulateToInactivateModifiers(TIP, modifiers, aWindow);
+  }
+}
+
+/**
+ * This is a wrapper around synthesizeKey that waits for the key event to be
+ * dispatched to the target content. It returns a promise which is resolved
+ * when the content receives the key event.
+ *
+ * This API is supposed to be used in those test cases that synthesize some
+ * input events to chrome process and have some checks in content.
+ */
+function synthesizeAndWaitKey(
+  aKey,
+  aEvent,
+  aWindow = window,
+  checkBeforeSynthesize,
+  checkAfterSynthesize
+) {
+  let browser = gBrowser.selectedTab.linkedBrowser;
+  let mm = browser.messageManager;
+  let keyCode = _createKeyboardEventDictionary(aKey, aEvent, null, aWindow)
+    .dictionary.keyCode;
+  let { ContentTask } = _EU_ChromeUtils.importESModule(
+    "resource://testing-common/ContentTask.sys.mjs"
+  );
+
+  let keyRegisteredPromise = new Promise(resolve => {
+    mm.addMessageListener("Test:KeyRegistered", function processed(message) {
+      mm.removeMessageListener("Test:KeyRegistered", processed);
+      resolve();
+    });
+  });
+  // eslint-disable-next-line no-shadow
+  let keyReceivedPromise = ContentTask.spawn(browser, keyCode, keyCode => {
+    return new Promise(resolve => {
+      addEventListener("keyup", function onKeyEvent(e) {
+        if (e.keyCode == keyCode) {
+          removeEventListener("keyup", onKeyEvent);
+          resolve();
+        }
+      });
+      sendAsyncMessage("Test:KeyRegistered");
+    });
+  });
+  keyRegisteredPromise.then(() => {
+    if (checkBeforeSynthesize) {
+      checkBeforeSynthesize();
+    }
+    synthesizeKey(aKey, aEvent, aWindow);
+    if (checkAfterSynthesize) {
+      checkAfterSynthesize();
+    }
+  });
+  return keyReceivedPromise;
+}
+
+function _parseNativeModifiers(aModifiers, aWindow = window) {
+  let modifiers = 0;
+  if (aModifiers.capsLockKey) {
+    modifiers |= SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_CAPS_LOCK;
+  }
+  if (aModifiers.numLockKey) {
+    modifiers |= SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_NUM_LOCK;
+  }
+  if (aModifiers.shiftKey) {
+    modifiers |= SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_SHIFT_LEFT;
+  }
+  if (aModifiers.shiftRightKey) {
+    modifiers |= SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_SHIFT_RIGHT;
+  }
+  if (aModifiers.ctrlKey) {
+    modifiers |=
+      SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_CONTROL_LEFT;
+  }
+  if (aModifiers.ctrlRightKey) {
+    modifiers |=
+      SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_CONTROL_RIGHT;
+  }
+  if (aModifiers.altKey) {
+    modifiers |= SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_ALT_LEFT;
+  }
+  if (aModifiers.altRightKey) {
+    modifiers |= SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_ALT_RIGHT;
+  }
+  if (aModifiers.metaKey) {
+    modifiers |=
+      SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_COMMAND_LEFT;
+  }
+  if (aModifiers.metaRightKey) {
+    modifiers |=
+      SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_COMMAND_RIGHT;
+  }
+  if (aModifiers.helpKey) {
+    modifiers |= SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_HELP;
+  }
+  if (aModifiers.fnKey) {
+    modifiers |= SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_FUNCTION;
+  }
+  if (aModifiers.numericKeyPadKey) {
+    modifiers |=
+      SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_NUMERIC_KEY_PAD;
+  }
+
+  if (aModifiers.accelKey) {
+    modifiers |= _EU_isMac(aWindow)
+      ? SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_COMMAND_LEFT
+      : SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_CONTROL_LEFT;
+  }
+  if (aModifiers.accelRightKey) {
+    modifiers |= _EU_isMac(aWindow)
+      ? SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_COMMAND_RIGHT
+      : SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_CONTROL_RIGHT;
+  }
+  if (aModifiers.altGrKey) {
+    modifiers |= _EU_isMac(aWindow)
+      ? SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_ALT_LEFT
+      : SpecialPowers.Ci.nsIDOMWindowUtils.NATIVE_MODIFIER_ALT_GRAPH;
+  }
+  return modifiers;
+}
+
+// Mac: Any unused number is okay for adding new keyboard layout.
+//      When you add new keyboard layout here, you need to modify
+//      TISInputSourceWrapper::InitByLayoutID().
+// Win: These constants can be found by inspecting registry keys under
+//      HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Keyboard Layouts
+
+const KEYBOARD_LAYOUT_ARABIC = {
+  name: "Arabic",
+  Mac: 6,
+  Win: 0x00000401,
+  hasAltGrOnWin: false,
+};
+const KEYBOARD_LAYOUT_ARABIC_PC = {
+  name: "Arabic - PC",
+  Mac: 7,
+  Win: null,
+  hasAltGrOnWin: false,
+};
+const KEYBOARD_LAYOUT_BRAZILIAN_ABNT = {
+  name: "Brazilian ABNT",
+  Mac: null,
+  Win: 0x00000416,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_DVORAK_QWERTY = {
+  name: "Dvorak-QWERTY",
+  Mac: 4,
+  Win: null,
+  hasAltGrOnWin: false,
+};
+const KEYBOARD_LAYOUT_EN_US = {
+  name: "US",
+  Mac: 0,
+  Win: 0x00000409,
+  hasAltGrOnWin: false,
+};
+const KEYBOARD_LAYOUT_FRENCH = {
+  name: "French",
+  Mac: 8,
+  Win: 0x0000040c,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_GREEK = {
+  name: "Greek",
+  Mac: 1,
+  Win: 0x00000408,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_GERMAN = {
+  name: "German",
+  Mac: 2,
+  Win: 0x00000407,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_HEBREW = {
+  name: "Hebrew",
+  Mac: 9,
+  Win: 0x0000040d,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_JAPANESE = {
+  name: "Japanese",
+  Mac: null,
+  Win: 0x00000411,
+  hasAltGrOnWin: false,
+};
+const KEYBOARD_LAYOUT_KHMER = {
+  name: "Khmer",
+  Mac: null,
+  Win: 0x00000453,
+  hasAltGrOnWin: true,
+}; // available on Win7 or later.
+const KEYBOARD_LAYOUT_LITHUANIAN = {
+  name: "Lithuanian",
+  Mac: 10,
+  Win: 0x00010427,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_NORWEGIAN = {
+  name: "Norwegian",
+  Mac: 11,
+  Win: 0x00000414,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_RUSSIAN_MNEMONIC = {
+  name: "Russian - Mnemonic",
+  Mac: null,
+  Win: 0x00020419,
+  hasAltGrOnWin: true,
+}; // available on Win8 or later.
+const KEYBOARD_LAYOUT_SPANISH = {
+  name: "Spanish",
+  Mac: 12,
+  Win: 0x0000040a,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_SWEDISH = {
+  name: "Swedish",
+  Mac: 3,
+  Win: 0x0000041d,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_THAI = {
+  name: "Thai",
+  Mac: 5,
+  Win: 0x0002041e,
+  hasAltGrOnWin: false,
+};
+
+/**
+ * synthesizeNativeKey() dispatches native key event on active window.
+ * This is implemented only on Windows and Mac. Note that this function
+ * dispatches the key event asynchronously and returns immediately. If a
+ * callback function is provided, the callback will be called upon
+ * completion of the key dispatch.
+ *
+ * @param aKeyboardLayout       One of KEYBOARD_LAYOUT_* defined above.
+ * @param aNativeKeyCode        A native keycode value defined in
+ *                              NativeKeyCodes.js.
+ * @param aModifiers            Modifier keys.  If no modifire key is pressed,
+ *                              this must be {}.  Otherwise, one or more items
+ *                              referred in _parseNativeModifiers() must be
+ *                              true.
+ * @param aChars                Specify characters which should be generated
+ *                              by the key event.
+ * @param aUnmodifiedChars      Specify characters of unmodified (except Shift)
+ *                              aChar value.
+ * @param aCallback             If provided, this callback will be invoked
+ *                              once the native keys have been processed
+ *                              by Gecko. Will never be called if this
+ *                              function returns false.
+ * @return                      True if this function succeed dispatching
+ *                              native key event.  Otherwise, false.
+ */
+
+function synthesizeNativeKey(
+  aKeyboardLayout,
+  aNativeKeyCode,
+  aModifiers,
+  aChars,
+  aUnmodifiedChars,
+  aCallback,
+  aWindow = window
+) {
+  var utils = _getDOMWindowUtils(aWindow);
+  if (!utils) {
+    return false;
+  }
+  var nativeKeyboardLayout = null;
+  if (_EU_isMac(aWindow)) {
+    nativeKeyboardLayout = aKeyboardLayout.Mac;
+  } else if (_EU_isWin(aWindow)) {
+    nativeKeyboardLayout = aKeyboardLayout.Win;
+  }
+  if (nativeKeyboardLayout === null) {
+    return false;
+  }
+
+  var observer = {
+    observe(aSubject, aTopic, aData) {
+      if (aCallback && aTopic == "keyevent") {
+        aCallback(aData);
+      }
+    },
+  };
+  utils.sendNativeKeyEvent(
+    nativeKeyboardLayout,
+    aNativeKeyCode,
+    _parseNativeModifiers(aModifiers, aWindow),
+    aChars,
+    aUnmodifiedChars,
+    observer
+  );
+  return true;
+}
+
+var _gSeenEvent = false;
+
+/**
+ * Indicate that an event with an original target of aExpectedTarget and
+ * a type of aExpectedEvent is expected to be fired, or not expected to
+ * be fired.
+ */
+function _expectEvent(aExpectedTarget, aExpectedEvent, aTestName) {
+  if (!aExpectedTarget || !aExpectedEvent) {
+    return null;
+  }
+
+  _gSeenEvent = false;
+
+  var type =
+    aExpectedEvent.charAt(0) == "!"
+      ? aExpectedEvent.substring(1)
+      : aExpectedEvent;
+  var eventHandler = function (event) {
+    var epassed =
+      !_gSeenEvent &&
+      event.originalTarget == aExpectedTarget &&
+      event.type == type;
+    is(
+      epassed,
+      true,
+      aTestName + " " + type + " event target " + (_gSeenEvent ? "twice" : "")
+    );
+    _gSeenEvent = true;
+  };
+
+  aExpectedTarget.addEventListener(type, eventHandler);
+  return eventHandler;
+}
+
+/**
+ * Check if the event was fired or not. The event handler aEventHandler
+ * will be removed.
+ */
+function _checkExpectedEvent(
+  aExpectedTarget,
+  aExpectedEvent,
+  aEventHandler,
+  aTestName
+) {
+  if (aEventHandler) {
+    var expectEvent = aExpectedEvent.charAt(0) != "!";
+    var type = expectEvent ? aExpectedEvent : aExpectedEvent.substring(1);
+    aExpectedTarget.removeEventListener(type, aEventHandler);
+    var desc = type + " event";
+    if (!expectEvent) {
+      desc += " not";
+    }
+    is(_gSeenEvent, expectEvent, aTestName + " " + desc + " fired");
+  }
+
+  _gSeenEvent = false;
+}
+
+/**
+ * Similar to synthesizeMouse except that a test is performed to see if an
+ * event is fired at the right target as a result.
+ *
+ * aExpectedTarget - the expected originalTarget of the event.
+ * aExpectedEvent - the expected type of the event, such as 'select'.
+ * aTestName - the test name when outputing results
+ *
+ * To test that an event is not fired, use an expected type preceded by an
+ * exclamation mark, such as '!select'. This might be used to test that a
+ * click on a disabled element doesn't fire certain events for instance.
+ *
+ * aWindow is optional, and defaults to the current window object.
+ */
+function synthesizeMouseExpectEvent(
+  aTarget,
+  aOffsetX,
+  aOffsetY,
+  aEvent,
+  aExpectedTarget,
+  aExpectedEvent,
+  aTestName,
+  aWindow
+) {
+  var eventHandler = _expectEvent(aExpectedTarget, aExpectedEvent, aTestName);
+  synthesizeMouse(aTarget, aOffsetX, aOffsetY, aEvent, aWindow);
+  _checkExpectedEvent(aExpectedTarget, aExpectedEvent, eventHandler, aTestName);
+}
+
+/**
+ * Similar to synthesizeKey except that a test is performed to see if an
+ * event is fired at the right target as a result.
+ *
+ * aExpectedTarget - the expected originalTarget of the event.
+ * aExpectedEvent - the expected type of the event, such as 'select'.
+ * aTestName - the test name when outputing results
+ *
+ * To test that an event is not fired, use an expected type preceded by an
+ * exclamation mark, such as '!select'.
+ *
+ * aWindow is optional, and defaults to the current window object.
+ */
+function synthesizeKeyExpectEvent(
+  key,
+  aEvent,
+  aExpectedTarget,
+  aExpectedEvent,
+  aTestName,
+  aWindow
+) {
+  var eventHandler = _expectEvent(aExpectedTarget, aExpectedEvent, aTestName);
+  synthesizeKey(key, aEvent, aWindow);
+  _checkExpectedEvent(aExpectedTarget, aExpectedEvent, eventHandler, aTestName);
+}
+
+function disableNonTestMouseEvents(aDisable) {
+  var domutils = _getDOMWindowUtils();
+  domutils.disableNonTestMouseEvents(aDisable);
+}
+
+function _getDOMWindowUtils(aWindow = window) {
+  // Leave this here as something, somewhere, passes a falsy argument
+  // to this, causing the |window| default argument not to get picked up.
+  if (!aWindow) {
+    aWindow = window;
+  }
+
+  // If documentURIObject exists or `window` is a stub object, we're in
+  // a chrome scope, so don't bother trying to go through SpecialPowers.
+  if (!window.document || window.document.documentURIObject) {
+    return aWindow.windowUtils;
+  }
+
+  // we need parent.SpecialPowers for:
+  //  layout/base/tests/test_reftests_with_caret.html
+  //  chrome: toolkit/content/tests/chrome/test_findbar.xul
+  //  chrome: toolkit/content/tests/chrome/test_popup_anchor.xul
+  if ("SpecialPowers" in window && window.SpecialPowers != undefined) {
+    return SpecialPowers.getDOMWindowUtils(aWindow);
+  }
+  if ("SpecialPowers" in parent && parent.SpecialPowers != undefined) {
+    return parent.SpecialPowers.getDOMWindowUtils(aWindow);
+  }
+
+  // TODO: this is assuming we are in chrome space
+  return aWindow.windowUtils;
+}
+
+function _defineConstant(name, value) {
+  Object.defineProperty(this, name, {
+    value,
+    enumerable: true,
+    writable: false,
+  });
+}
+
+const COMPOSITION_ATTR_RAW_CLAUSE =
+  _EU_Ci.nsITextInputProcessor.ATTR_RAW_CLAUSE;
+_defineConstant("COMPOSITION_ATTR_RAW_CLAUSE", COMPOSITION_ATTR_RAW_CLAUSE);
+const COMPOSITION_ATTR_SELECTED_RAW_CLAUSE =
+  _EU_Ci.nsITextInputProcessor.ATTR_SELECTED_RAW_CLAUSE;
+_defineConstant(
+  "COMPOSITION_ATTR_SELECTED_RAW_CLAUSE",
+  COMPOSITION_ATTR_SELECTED_RAW_CLAUSE
+);
+const COMPOSITION_ATTR_CONVERTED_CLAUSE =
+  _EU_Ci.nsITextInputProcessor.ATTR_CONVERTED_CLAUSE;
+_defineConstant(
+  "COMPOSITION_ATTR_CONVERTED_CLAUSE",
+  COMPOSITION_ATTR_CONVERTED_CLAUSE
+);
+const COMPOSITION_ATTR_SELECTED_CLAUSE =
+  _EU_Ci.nsITextInputProcessor.ATTR_SELECTED_CLAUSE;
+_defineConstant(
+  "COMPOSITION_ATTR_SELECTED_CLAUSE",
+  COMPOSITION_ATTR_SELECTED_CLAUSE
+);
+
+var TIPMap = new WeakMap();
+
+function _getTIP(aWindow, aCallback) {
+  if (!aWindow) {
+    aWindow = window;
+  }
+  var tip;
+  if (TIPMap.has(aWindow)) {
+    tip = TIPMap.get(aWindow);
+  } else {
+    tip = _EU_Cc["@mozilla.org/text-input-processor;1"].createInstance(
+      _EU_Ci.nsITextInputProcessor
+    );
+    TIPMap.set(aWindow, tip);
+  }
+  if (!tip.beginInputTransactionForTests(aWindow, aCallback)) {
+    tip = null;
+    TIPMap.delete(aWindow);
+  }
+  return tip;
+}
+
+function _getKeyboardEvent(aWindow = window) {
+  if (typeof KeyboardEvent != "undefined") {
+    try {
+      // See if the object can be instantiated; sometimes this yields
+      // 'TypeError: can't access dead object' or 'KeyboardEvent is not a constructor'.
+      new KeyboardEvent("", {});
+      return KeyboardEvent;
+    } catch (ex) {}
+  }
+  if (typeof content != "undefined" && "KeyboardEvent" in content) {
+    return content.KeyboardEvent;
+  }
+  return aWindow.KeyboardEvent;
+}
+
+// eslint-disable-next-line complexity
+function _guessKeyNameFromKeyCode(aKeyCode, aWindow = window) {
+  var KeyboardEvent = _getKeyboardEvent(aWindow);
+  switch (aKeyCode) {
+    case KeyboardEvent.DOM_VK_CANCEL:
+      return "Cancel";
+    case KeyboardEvent.DOM_VK_HELP:
+      return "Help";
+    case KeyboardEvent.DOM_VK_BACK_SPACE:
+      return "Backspace";
+    case KeyboardEvent.DOM_VK_TAB:
+      return "Tab";
+    case KeyboardEvent.DOM_VK_CLEAR:
+      return "Clear";
+    case KeyboardEvent.DOM_VK_RETURN:
+      return "Enter";
+    case KeyboardEvent.DOM_VK_SHIFT:
+      return "Shift";
+    case KeyboardEvent.DOM_VK_CONTROL:
+      return "Control";
+    case KeyboardEvent.DOM_VK_ALT:
+      return "Alt";
+    case KeyboardEvent.DOM_VK_PAUSE:
+      return "Pause";
+    case KeyboardEvent.DOM_VK_EISU:
+      return "Eisu";
+    case KeyboardEvent.DOM_VK_ESCAPE:
+      return "Escape";
+    case KeyboardEvent.DOM_VK_CONVERT:
+      return "Convert";
+    case KeyboardEvent.DOM_VK_NONCONVERT:
+      return "NonConvert";
+    case KeyboardEvent.DOM_VK_ACCEPT:
+      return "Accept";
+    case KeyboardEvent.DOM_VK_MODECHANGE:
+      return "ModeChange";
+    case KeyboardEvent.DOM_VK_PAGE_UP:
+      return "PageUp";
+    case KeyboardEvent.DOM_VK_PAGE_DOWN:
+      return "PageDown";
+    case KeyboardEvent.DOM_VK_END:
+      return "End";
+    case KeyboardEvent.DOM_VK_HOME:
+      return "Home";
+    case KeyboardEvent.DOM_VK_LEFT:
+      return "ArrowLeft";
+    case KeyboardEvent.DOM_VK_UP:
+      return "ArrowUp";
+    case KeyboardEvent.DOM_VK_RIGHT:
+      return "ArrowRight";
+    case KeyboardEvent.DOM_VK_DOWN:
+      return "ArrowDown";
+    case KeyboardEvent.DOM_VK_SELECT:
+      return "Select";
+    case KeyboardEvent.DOM_VK_PRINT:
+      return "Print";
+    case KeyboardEvent.DOM_VK_EXECUTE:
+      return "Execute";
+    case KeyboardEvent.DOM_VK_PRINTSCREEN:
+      return "PrintScreen";
+    case KeyboardEvent.DOM_VK_INSERT:
+      return "Insert";
+    case KeyboardEvent.DOM_VK_DELETE:
+      return "Delete";
+    case KeyboardEvent.DOM_VK_WIN:
+      return "OS";
+    case KeyboardEvent.DOM_VK_CONTEXT_MENU:
+      return "ContextMenu";
+    case KeyboardEvent.DOM_VK_SLEEP:
+      return "Standby";
+    case KeyboardEvent.DOM_VK_F1:
+      return "F1";
+    case KeyboardEvent.DOM_VK_F2:
+      return "F2";
+    case KeyboardEvent.DOM_VK_F3:
+      return "F3";
+    case KeyboardEvent.DOM_VK_F4:
+      return "F4";
+    case KeyboardEvent.DOM_VK_F5:
+      return "F5";
+    case KeyboardEvent.DOM_VK_F6:
+      return "F6";
+    case KeyboardEvent.DOM_VK_F7:
+      return "F7";
+    case KeyboardEvent.DOM_VK_F8:
+      return "F8";
+    case KeyboardEvent.DOM_VK_F9:
+      return "F9";
+    case KeyboardEvent.DOM_VK_F10:
+      return "F10";
+    case KeyboardEvent.DOM_VK_F11:
+      return "F11";
+    case KeyboardEvent.DOM_VK_F12:
+      return "F12";
+    case KeyboardEvent.DOM_VK_F13:
+      return "F13";
+    case KeyboardEvent.DOM_VK_F14:
+      return "F14";
+    case KeyboardEvent.DOM_VK_F15:
+      return "F15";
+    case KeyboardEvent.DOM_VK_F16:
+      return "F16";
+    case KeyboardEvent.DOM_VK_F17:
+      return "F17";
+    case KeyboardEvent.DOM_VK_F18:
+      return "F18";
+    case KeyboardEvent.DOM_VK_F19:
+      return "F19";
+    case KeyboardEvent.DOM_VK_F20:
+      return "F20";
+    case KeyboardEvent.DOM_VK_F21:
+      return "F21";
+    case KeyboardEvent.DOM_VK_F22:
+      return "F22";
+    case KeyboardEvent.DOM_VK_F23:
+      return "F23";
+    case KeyboardEvent.DOM_VK_F24:
+      return "F24";
+    case KeyboardEvent.DOM_VK_NUM_LOCK:
+      return "NumLock";
+    case KeyboardEvent.DOM_VK_SCROLL_LOCK:
+      return "ScrollLock";
+    case KeyboardEvent.DOM_VK_VOLUME_MUTE:
+      return "AudioVolumeMute";
+    case KeyboardEvent.DOM_VK_VOLUME_DOWN:
+      return "AudioVolumeDown";
+    case KeyboardEvent.DOM_VK_VOLUME_UP:
+      return "AudioVolumeUp";
+    case KeyboardEvent.DOM_VK_META:
+      return "Meta";
+    case KeyboardEvent.DOM_VK_ALTGR:
+      return "AltGraph";
+    case KeyboardEvent.DOM_VK_PROCESSKEY:
+      return "Process";
+    case KeyboardEvent.DOM_VK_ATTN:
+      return "Attn";
+    case KeyboardEvent.DOM_VK_CRSEL:
+      return "CrSel";
+    case KeyboardEvent.DOM_VK_EXSEL:
+      return "ExSel";
+    case KeyboardEvent.DOM_VK_EREOF:
+      return "EraseEof";
+    case KeyboardEvent.DOM_VK_PLAY:
+      return "Play";
+    default:
+      return "Unidentified";
+  }
+}
+
+function _createKeyboardEventDictionary(
+  aKey,
+  aKeyEvent,
+  aTIP = null,
+  aWindow = window
+) {
+  var result = { dictionary: null, flags: 0 };
+  var keyCodeIsDefined = "keyCode" in aKeyEvent;
+  var keyCode =
+    keyCodeIsDefined && aKeyEvent.keyCode >= 0 && aKeyEvent.keyCode <= 255
+      ? aKeyEvent.keyCode
+      : 0;
+  var keyName = "Unidentified";
+  var code = aKeyEvent.code;
+  if (!aTIP) {
+    aTIP = _getTIP(aWindow);
+  }
+  if (aKey.indexOf("KEY_") == 0) {
+    keyName = aKey.substr("KEY_".length);
+    result.flags |= _EU_Ci.nsITextInputProcessor.KEY_NON_PRINTABLE_KEY;
+    if (code === undefined) {
+      code = aTIP.computeCodeValueOfNonPrintableKey(
+        keyName,
+        aKeyEvent.location
+      );
+    }
+  } else if (aKey.indexOf("VK_") == 0) {
+    keyCode = _getKeyboardEvent(aWindow)["DOM_" + aKey];
+    if (!keyCode) {
+      throw new Error("Unknown key: " + aKey);
+    }
+    keyName = _guessKeyNameFromKeyCode(keyCode, aWindow);
+    result.flags |= _EU_Ci.nsITextInputProcessor.KEY_NON_PRINTABLE_KEY;
+    if (code === undefined) {
+      code = aTIP.computeCodeValueOfNonPrintableKey(
+        keyName,
+        aKeyEvent.location
+      );
+    }
+  } else if (aKey != "") {
+    keyName = aKey;
+    if (!keyCodeIsDefined) {
+      keyCode = aTIP.guessKeyCodeValueOfPrintableKeyInUSEnglishKeyboardLayout(
+        aKey,
+        aKeyEvent.location
+      );
+    }
+    if (!keyCode) {
+      result.flags |= _EU_Ci.nsITextInputProcessor.KEY_KEEP_KEYCODE_ZERO;
+    }
+    result.flags |= _EU_Ci.nsITextInputProcessor.KEY_FORCE_PRINTABLE_KEY;
+    if (code === undefined) {
+      code = aTIP.guessCodeValueOfPrintableKeyInUSEnglishKeyboardLayout(
+        keyName,
+        aKeyEvent.location
+      );
+    }
+  }
+  var locationIsDefined = "location" in aKeyEvent;
+  if (locationIsDefined && aKeyEvent.location === 0) {
+    result.flags |= _EU_Ci.nsITextInputProcessor.KEY_KEEP_KEY_LOCATION_STANDARD;
+  }
+  if (aKeyEvent.doNotMarkKeydownAsProcessed) {
+    result.flags |=
+      _EU_Ci.nsITextInputProcessor.KEY_DONT_MARK_KEYDOWN_AS_PROCESSED;
+  }
+  if (aKeyEvent.markKeyupAsProcessed) {
+    result.flags |= _EU_Ci.nsITextInputProcessor.KEY_MARK_KEYUP_AS_PROCESSED;
+  }
+  result.dictionary = {
+    key: keyName,
+    code,
+    location: locationIsDefined ? aKeyEvent.location : 0,
+    repeat: "repeat" in aKeyEvent ? aKeyEvent.repeat === true : false,
+    keyCode,
+  };
+  return result;
+}
+
+function _emulateToActivateModifiers(aTIP, aKeyEvent, aWindow = window) {
+  if (!aKeyEvent) {
+    return null;
+  }
+  var KeyboardEvent = _getKeyboardEvent(aWindow);
+
+  var modifiers = {
+    normal: [
+      { key: "Alt", attr: "altKey" },
+      { key: "AltGraph", attr: "altGraphKey" },
+      { key: "Control", attr: "ctrlKey" },
+      { key: "Fn", attr: "fnKey" },
+      { key: "Meta", attr: "metaKey" },
+      { key: "OS", attr: "osKey" },
+      { key: "Shift", attr: "shiftKey" },
+      { key: "Symbol", attr: "symbolKey" },
+      { key: _EU_isMac(aWindow) ? "Meta" : "Control", attr: "accelKey" },
+    ],
+    lockable: [
+      { key: "CapsLock", attr: "capsLockKey" },
+      { key: "FnLock", attr: "fnLockKey" },
+      { key: "NumLock", attr: "numLockKey" },
+      { key: "ScrollLock", attr: "scrollLockKey" },
+      { key: "SymbolLock", attr: "symbolLockKey" },
+    ],
+  };
+
+  for (let i = 0; i < modifiers.normal.length; i++) {
+    if (!aKeyEvent[modifiers.normal[i].attr]) {
+      continue;
+    }
+    if (aTIP.getModifierState(modifiers.normal[i].key)) {
+      continue; // already activated.
+    }
+    let event = new KeyboardEvent("", { key: modifiers.normal[i].key });
+    aTIP.keydown(
+      event,
+      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT
+    );
+    modifiers.normal[i].activated = true;
+  }
+  for (let i = 0; i < modifiers.lockable.length; i++) {
+    if (!aKeyEvent[modifiers.lockable[i].attr]) {
+      continue;
+    }
+    if (aTIP.getModifierState(modifiers.lockable[i].key)) {
+      continue; // already activated.
+    }
+    let event = new KeyboardEvent("", { key: modifiers.lockable[i].key });
+    aTIP.keydown(
+      event,
+      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT
+    );
+    aTIP.keyup(
+      event,
+      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT
+    );
+    modifiers.lockable[i].activated = true;
+  }
+  return modifiers;
+}
+
+function _emulateToInactivateModifiers(aTIP, aModifiers, aWindow = window) {
+  if (!aModifiers) {
+    return;
+  }
+  var KeyboardEvent = _getKeyboardEvent(aWindow);
+  for (let i = 0; i < aModifiers.normal.length; i++) {
+    if (!aModifiers.normal[i].activated) {
+      continue;
+    }
+    let event = new KeyboardEvent("", { key: aModifiers.normal[i].key });
+    aTIP.keyup(
+      event,
+      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT
+    );
+  }
+  for (let i = 0; i < aModifiers.lockable.length; i++) {
+    if (!aModifiers.lockable[i].activated) {
+      continue;
+    }
+    if (!aTIP.getModifierState(aModifiers.lockable[i].key)) {
+      continue; // who already inactivated this?
+    }
+    let event = new KeyboardEvent("", { key: aModifiers.lockable[i].key });
+    aTIP.keydown(
+      event,
+      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT
+    );
+    aTIP.keyup(
+      event,
+      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT
+    );
+  }
+}
+
+/**
+ * Synthesize a composition event and keydown event and keyup events unless
+ * you prevent to dispatch them explicitly (see aEvent.key's explanation).
+ *
+ * Note that you shouldn't call this with "compositionstart" unless you need to
+ * test compositionstart event which is NOT followed by compositionupdate
+ * event immediately.  Typically, native IME starts composition with
+ * a pair of keydown and keyup event and dispatch compositionstart and
+ * compositionupdate (and non-standard text event) between them.  So, in most
+ * cases, you should call synthesizeCompositionChange() directly.
+ * If you call this with compositionstart, keyup event will be fired
+ * immediately after compositionstart.  In other words, you should use
+ * "compositionstart" only when you need to emulate IME which just starts
+ * composition with compositionstart event but does not send composing text to
+ * us until committing the composition.  This is behavior of some Chinese IMEs.
+ *
+ * @param aEvent               The composition event information.  This must
+ *                             have |type| member.  The value must be
+ *                             "compositionstart", "compositionend",
+ *                             "compositioncommitasis" or "compositioncommit".
+ *
+ *                             And also this may have |data| and |locale| which
+ *                             would be used for the value of each property of
+ *                             the composition event.  Note that the |data| is
+ *                             ignored if the event type is "compositionstart"
+ *                             or "compositioncommitasis".
+ *
+ *                             If |key| is undefined, "keydown" and "keyup"
+ *                             events which are marked as "processed by IME"
+ *                             are dispatched.  If |key| is not null, "keydown"
+ *                             and/or "keyup" events are dispatched (if the
+ *                             |key.type| is specified as "keydown", only
+ *                             "keydown" event is dispatched).  Otherwise,
+ *                             i.e., if |key| is null, neither "keydown" nor
+ *                             "keyup" event is dispatched.
+ *
+ *                             If |key.doNotMarkKeydownAsProcessed| is not true,
+ *                             key value and keyCode value of "keydown" event
+ *                             will be set to "Process" and DOM_VK_PROCESSKEY.
+ *                             If |key.markKeyupAsProcessed| is true,
+ *                             key value and keyCode value of "keyup" event
+ *                             will be set to "Process" and DOM_VK_PROCESSKEY.
+ * @param aWindow              Optional (If null, current |window| will be used)
+ * @param aCallback            Optional (If non-null, use the callback for
+ *                             receiving notifications to IME)
+ */
+function synthesizeComposition(aEvent, aWindow = window, aCallback) {
+  var TIP = _getTIP(aWindow, aCallback);
+  if (!TIP) {
+    return;
+  }
+  var KeyboardEvent = _getKeyboardEvent(aWindow);
+  var modifiers = _emulateToActivateModifiers(TIP, aEvent.key, aWindow);
+  var keyEventDict = { dictionary: null, flags: 0 };
+  var keyEvent = null;
+  if (aEvent.key && typeof aEvent.key.key === "string") {
+    keyEventDict = _createKeyboardEventDictionary(
+      aEvent.key.key,
+      aEvent.key,
+      TIP,
+      aWindow
+    );
+    keyEvent = new KeyboardEvent(
+      // eslint-disable-next-line no-nested-ternary
+      aEvent.key.type === "keydown"
+        ? "keydown"
+        : aEvent.key.type === "keyup"
+        ? "keyup"
+        : "",
+      keyEventDict.dictionary
+    );
+  } else if (aEvent.key === undefined) {
+    keyEventDict = _createKeyboardEventDictionary(
+      "KEY_Process",
+      {},
+      TIP,
+      aWindow
+    );
+    keyEvent = new KeyboardEvent("", keyEventDict.dictionary);
+  }
+  try {
+    switch (aEvent.type) {
+      case "compositionstart":
+        TIP.startComposition(keyEvent, keyEventDict.flags);
+        break;
+      case "compositioncommitasis":
+        TIP.commitComposition(keyEvent, keyEventDict.flags);
+        break;
+      case "compositioncommit":
+        TIP.commitCompositionWith(aEvent.data, keyEvent, keyEventDict.flags);
+        break;
+    }
+  } finally {
+    _emulateToInactivateModifiers(TIP, modifiers, aWindow);
+  }
+}
+/**
+ * Synthesize eCompositionChange event which causes a DOM text event, may
+ * cause compositionupdate event, and causes keydown event and keyup event
+ * unless you prevent to dispatch them explicitly (see aEvent.key's
+ * explanation).
+ *
+ * Note that if you call this when there is no composition, compositionstart
+ * event will be fired automatically.  This is better than you use
+ * synthesizeComposition("compositionstart") in most cases.  See the
+ * explanation of synthesizeComposition().
+ *
+ * @param aEvent   The compositionchange event's information, this has
+ *                 |composition| and |caret| members.  |composition| has
+ *                 |string| and |clauses| members.  |clauses| must be array
+ *                 object.  Each object has |length| and |attr|.  And |caret|
+ *                 has |start| and |length|.  See the following tree image.
+ *
+ *                 aEvent
+ *                   +-- composition
+ *                   |     +-- string
+ *                   |     +-- clauses[]
+ *                   |           +-- length
+ *                   |           +-- attr
+ *                   +-- caret
+ *                   |     +-- start
+ *                   |     +-- length
+ *                   +-- key
+ *
+ *                 Set the composition string to |composition.string|.  Set its
+ *                 clauses information to the |clauses| array.
+ *
+ *                 When it's composing, set the each clauses' length to the
+ *                 |composition.clauses[n].length|.  The sum of the all length
+ *                 values must be same as the length of |composition.string|.
+ *                 Set nsICompositionStringSynthesizer.ATTR_* to the
+ *                 |composition.clauses[n].attr|.
+ *
+ *                 When it's not composing, set 0 to the
+ *                 |composition.clauses[0].length| and
+ *                 |composition.clauses[0].attr|.
+ *
+ *                 Set caret position to the |caret.start|. It's offset from
+ *                 the start of the composition string.  Set caret length to
+ *                 |caret.length|.  If it's larger than 0, it should be wide
+ *                 caret.  However, current nsEditor doesn't support wide
+ *                 caret, therefore, you should always set 0 now.
+ *
+ *                 If |key| is undefined, "keydown" and "keyup" events which
+ *                 are marked as "processed by IME" are dispatched.  If |key|
+ *                 is not null, "keydown" and/or "keyup" events are dispatched
+ *                 (if the |key.type| is specified as "keydown", only "keydown"
+ *                 event is dispatched).  Otherwise, i.e., if |key| is null,
+ *                 neither "keydown" nor "keyup" event is dispatched.
+ *                 If |key.doNotMarkKeydownAsProcessed| is not true, key value
+ *                 and keyCode value of "keydown" event will be set to
+ *                 "Process" and DOM_VK_PROCESSKEY.
+ *                 If |key.markKeyupAsProcessed| is true key value and keyCode
+ *                 value of "keyup" event will be set to "Process" and
+ *                 DOM_VK_PROCESSKEY.
+ *
+ * @param aWindow  Optional (If null, current |window| will be used)
+ * @param aCallback     Optional (If non-null, use the callback for receiving
+ *                      notifications to IME)
+ */
+function synthesizeCompositionChange(aEvent, aWindow = window, aCallback) {
+  var TIP = _getTIP(aWindow, aCallback);
+  if (!TIP) {
+    return;
+  }
+  var KeyboardEvent = _getKeyboardEvent(aWindow);
+
+  if (
+    !aEvent.composition ||
+    !aEvent.composition.clauses ||
+    !aEvent.composition.clauses[0]
+  ) {
+    return;
+  }
+
+  TIP.setPendingCompositionString(aEvent.composition.string);
+  if (aEvent.composition.clauses[0].length) {
+    for (var i = 0; i < aEvent.composition.clauses.length; i++) {
+      switch (aEvent.composition.clauses[i].attr) {
+        case TIP.ATTR_RAW_CLAUSE:
+        case TIP.ATTR_SELECTED_RAW_CLAUSE:
+        case TIP.ATTR_CONVERTED_CLAUSE:
+        case TIP.ATTR_SELECTED_CLAUSE:
+          TIP.appendClauseToPendingComposition(
+            aEvent.composition.clauses[i].length,
+            aEvent.composition.clauses[i].attr
+          );
+          break;
+        case 0:
+          // Ignore dummy clause for the argument.
+          break;
+        default:
+          throw new Error("invalid clause attribute specified");
+      }
+    }
+  }
+
+  if (aEvent.caret) {
+    TIP.setCaretInPendingComposition(aEvent.caret.start);
+  }
+
+  var modifiers = _emulateToActivateModifiers(TIP, aEvent.key, aWindow);
+  try {
+    var keyEventDict = { dictionary: null, flags: 0 };
+    var keyEvent = null;
+    if (aEvent.key && typeof aEvent.key.key === "string") {
+      keyEventDict = _createKeyboardEventDictionary(
+        aEvent.key.key,
+        aEvent.key,
+        TIP,
+        aWindow
+      );
+      keyEvent = new KeyboardEvent(
+        // eslint-disable-next-line no-nested-ternary
+        aEvent.key.type === "keydown"
+          ? "keydown"
+          : aEvent.key.type === "keyup"
+          ? "keyup"
+          : "",
+        keyEventDict.dictionary
+      );
+    } else if (aEvent.key === undefined) {
+      keyEventDict = _createKeyboardEventDictionary(
+        "KEY_Process",
+        {},
+        TIP,
+        aWindow
+      );
+      keyEvent = new KeyboardEvent("", keyEventDict.dictionary);
+    }
+    TIP.flushPendingComposition(keyEvent, keyEventDict.flags);
+  } finally {
+    _emulateToInactivateModifiers(TIP, modifiers, aWindow);
+  }
+}
+
+// Must be synchronized with nsIDOMWindowUtils.
+const QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK = 0x0000;
+const QUERY_CONTENT_FLAG_USE_XP_LINE_BREAK = 0x0001;
+
+const QUERY_CONTENT_FLAG_SELECTION_NORMAL = 0x0000;
+const QUERY_CONTENT_FLAG_SELECTION_SPELLCHECK = 0x0002;
+const QUERY_CONTENT_FLAG_SELECTION_IME_RAWINPUT = 0x0004;
+const QUERY_CONTENT_FLAG_SELECTION_IME_SELECTEDRAWTEXT = 0x0008;
+const QUERY_CONTENT_FLAG_SELECTION_IME_CONVERTEDTEXT = 0x0010;
+const QUERY_CONTENT_FLAG_SELECTION_IME_SELECTEDCONVERTEDTEXT = 0x0020;
+const QUERY_CONTENT_FLAG_SELECTION_ACCESSIBILITY = 0x0040;
+const QUERY_CONTENT_FLAG_SELECTION_FIND = 0x0080;
+const QUERY_CONTENT_FLAG_SELECTION_URLSECONDARY = 0x0100;
+const QUERY_CONTENT_FLAG_SELECTION_URLSTRIKEOUT = 0x0200;
+
+const QUERY_CONTENT_FLAG_OFFSET_RELATIVE_TO_INSERTION_POINT = 0x0400;
+
+const SELECTION_SET_FLAG_USE_NATIVE_LINE_BREAK = 0x0000;
+const SELECTION_SET_FLAG_USE_XP_LINE_BREAK = 0x0001;
+const SELECTION_SET_FLAG_REVERSE = 0x0002;
+
+/**
+ * Synthesize a query text content event.
+ *
+ * @param aOffset  The character offset.  0 means the first character in the
+ *                 selection root.
+ * @param aLength  The length of getting text.  If the length is too long,
+ *                 the extra length is ignored.
+ * @param aIsRelative   Optional (If true, aOffset is relative to start of
+ *                      composition if there is, or start of selection.)
+ * @param aWindow  Optional (If null, current |window| will be used)
+ * @return         An nsIQueryContentEventResult object.  If this failed,
+ *                 the result might be null.
+ */
+function synthesizeQueryTextContent(aOffset, aLength, aIsRelative, aWindow) {
+  var utils = _getDOMWindowUtils(aWindow);
+  if (!utils) {
+    return null;
+  }
+  var flags = QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK;
+  if (aIsRelative === true) {
+    flags |= QUERY_CONTENT_FLAG_OFFSET_RELATIVE_TO_INSERTION_POINT;
+  }
+  return utils.sendQueryContentEvent(
+    utils.QUERY_TEXT_CONTENT,
+    aOffset,
+    aLength,
+    0,
+    0,
+    flags
+  );
+}
+
+/**
+ * Synthesize a query selected text event.
+ *
+ * @param aSelectionType    Optional, one of QUERY_CONTENT_FLAG_SELECTION_*.
+ *                          If null, QUERY_CONTENT_FLAG_SELECTION_NORMAL will
+ *                          be used.
+ * @param aWindow  Optional (If null, current |window| will be used)
+ * @return         An nsIQueryContentEventResult object.  If this failed,
+ *                 the result might be null.
+ */
+function synthesizeQuerySelectedText(aSelectionType, aWindow) {
+  var utils = _getDOMWindowUtils(aWindow);
+  var flags = QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK;
+  if (aSelectionType) {
+    flags |= aSelectionType;
+  }
+
+  return utils.sendQueryContentEvent(
+    utils.QUERY_SELECTED_TEXT,
+    0,
+    0,
+    0,
+    0,
+    flags
+  );
+}
+
+/**
+ * Synthesize a query caret rect event.
+ *
+ * @param aOffset  The caret offset.  0 means left side of the first character
+ *                 in the selection root.
+ * @param aWindow  Optional (If null, current |window| will be used)
+ * @return         An nsIQueryContentEventResult object.  If this failed,
+ *                 the result might be null.
+ */
+function synthesizeQueryCaretRect(aOffset, aWindow) {
+  var utils = _getDOMWindowUtils(aWindow);
+  if (!utils) {
+    return null;
+  }
+  return utils.sendQueryContentEvent(
+    utils.QUERY_CARET_RECT,
+    aOffset,
+    0,
+    0,
+    0,
+    QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK
+  );
+}
+
+/**
+ * Synthesize a selection set event.
+ *
+ * @param aOffset  The character offset.  0 means the first character in the
+ *                 selection root.
+ * @param aLength  The length of the text.  If the length is too long,
+ *                 the extra length is ignored.
+ * @param aReverse If true, the selection is from |aOffset + aLength| to
+ *                 |aOffset|.  Otherwise, from |aOffset| to |aOffset + aLength|.
+ * @param aWindow  Optional (If null, current |window| will be used)
+ * @return         True, if succeeded.  Otherwise false.
+ */
+async function synthesizeSelectionSet(
+  aOffset,
+  aLength,
+  aReverse,
+  aWindow = window
+) {
+  const utils = _getDOMWindowUtils(aWindow);
+  if (!utils) {
+    return false;
+  }
+  // eSetSelection event will be compared with selection cache in
+  // IMEContentObserver, but it may have not been updated yet.  Therefore, we
+  // need to flush pending things of IMEContentObserver.
+  await new Promise(resolve =>
+    aWindow.requestAnimationFrame(() => aWindow.requestAnimationFrame(resolve))
+  );
+  const flags = aReverse ? SELECTION_SET_FLAG_REVERSE : 0;
+  return utils.sendSelectionSetEvent(aOffset, aLength, flags);
+}
+
+/**
+ * Synthesize a query text rect event.
+ *
+ * @param aOffset  The character offset.  0 means the first character in the
+ *                 selection root.
+ * @param aLength  The length of the text.  If the length is too long,
+ *                 the extra length is ignored.
+ * @param aIsRelative   Optional (If true, aOffset is relative to start of
+ *                      composition if there is, or start of selection.)
+ * @param aWindow  Optional (If null, current |window| will be used)
+ * @return         An nsIQueryContentEventResult object.  If this failed,
+ *                 the result might be null.
+ */
+function synthesizeQueryTextRect(aOffset, aLength, aIsRelative, aWindow) {
+  if (aIsRelative !== undefined && typeof aIsRelative !== "boolean") {
+    throw new Error(
+      "Maybe, you set Window object to the 3rd argument, but it should be a boolean value"
+    );
+  }
+  var utils = _getDOMWindowUtils(aWindow);
+  let flags = QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK;
+  if (aIsRelative === true) {
+    flags |= QUERY_CONTENT_FLAG_OFFSET_RELATIVE_TO_INSERTION_POINT;
+  }
+  return utils.sendQueryContentEvent(
+    utils.QUERY_TEXT_RECT,
+    aOffset,
+    aLength,
+    0,
+    0,
+    flags
+  );
+}
+
+/**
+ * Synthesize a query text rect array event.
+ *
+ * @param aOffset  The character offset.  0 means the first character in the
+ *                 selection root.
+ * @param aLength  The length of the text.  If the length is too long,
+ *                 the extra length is ignored.
+ * @param aWindow  Optional (If null, current |window| will be used)
+ * @return         An nsIQueryContentEventResult object.  If this failed,
+ *                 the result might be null.
+ */
+function synthesizeQueryTextRectArray(aOffset, aLength, aWindow) {
+  var utils = _getDOMWindowUtils(aWindow);
+  return utils.sendQueryContentEvent(
+    utils.QUERY_TEXT_RECT_ARRAY,
+    aOffset,
+    aLength,
+    0,
+    0,
+    QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK
+  );
+}
+
+/**
+ * Synthesize a query editor rect event.
+ *
+ * @param aWindow  Optional (If null, current |window| will be used)
+ * @return         An nsIQueryContentEventResult object.  If this failed,
+ *                 the result might be null.
+ */
+function synthesizeQueryEditorRect(aWindow) {
+  var utils = _getDOMWindowUtils(aWindow);
+  return utils.sendQueryContentEvent(
+    utils.QUERY_EDITOR_RECT,
+    0,
+    0,
+    0,
+    0,
+    QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK
+  );
+}
+
+/**
+ * Synthesize a character at point event.
+ *
+ * @param aX, aY   The offset in the client area of the DOM window.
+ * @param aWindow  Optional (If null, current |window| will be used)
+ * @return         An nsIQueryContentEventResult object.  If this failed,
+ *                 the result might be null.
+ */
+function synthesizeCharAtPoint(aX, aY, aWindow) {
+  var utils = _getDOMWindowUtils(aWindow);
+  return utils.sendQueryContentEvent(
+    utils.QUERY_CHARACTER_AT_POINT,
+    0,
+    0,
+    aX,
+    aY,
+    QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK
+  );
+}
+
+/**
+ * INTERNAL USE ONLY
+ * Create an event object to pass to sendDragEvent.
+ *
+ * @param aType          The string represents drag event type.
+ * @param aDestElement   The element to fire the drag event, used to calculate
+ *                       screenX/Y and clientX/Y.
+ * @param aDestWindow    Optional; Defaults to the current window object.
+ * @param aDataTransfer  dataTransfer for current drag session.
+ * @param aDragEvent     The object contains properties to override the event
+ *                       object
+ * @return               An object to pass to sendDragEvent.
+ */
+function createDragEventObject(
+  aType,
+  aDestElement,
+  aDestWindow,
+  aDataTransfer,
+  aDragEvent
+) {
+  var destRect = aDestElement.getBoundingClientRect();
+  var destClientX = destRect.left + destRect.width / 2;
+  var destClientY = destRect.top + destRect.height / 2;
+  var destScreenX = aDestWindow.mozInnerScreenX + destClientX;
+  var destScreenY = aDestWindow.mozInnerScreenY + destClientY;
+  if ("clientX" in aDragEvent && !("screenX" in aDragEvent)) {
+    aDragEvent.screenX = aDestWindow.mozInnerScreenX + aDragEvent.clientX;
+  }
+  if ("clientY" in aDragEvent && !("screenY" in aDragEvent)) {
+    aDragEvent.screenY = aDestWindow.mozInnerScreenY + aDragEvent.clientY;
+  }
+
+  // Wrap only in plain mochitests
+  let dataTransfer;
+  if (aDataTransfer) {
+    dataTransfer = _EU_maybeUnwrap(
+      _EU_maybeWrap(aDataTransfer).mozCloneForEvent(aType)
+    );
+
+    // Copy over the drop effect. This isn't copied over by Clone, as it uses
+    // more complex logic in the actual implementation (see
+    // nsContentUtils::SetDataTransferInEvent for actual impl).
+    dataTransfer.dropEffect = aDataTransfer.dropEffect;
+  }
+
+  return Object.assign(
+    {
+      type: aType,
+      screenX: destScreenX,
+      screenY: destScreenY,
+      clientX: destClientX,
+      clientY: destClientY,
+      dataTransfer,
+      _domDispatchOnly: aDragEvent._domDispatchOnly,
+    },
+    aDragEvent
+  );
+}
+
+/**
+ * Emulate a event sequence of dragstart, dragenter, and dragover.
+ *
+ * @param {Element} aSrcElement
+ *        The element to use to start the drag.
+ * @param {Element} aDestElement
+ *        The element to fire the dragover, dragenter events
+ * @param {Array}   aDragData
+ *        The data to supply for the data transfer.
+ *        This data is in the format:
+ *
+ *        [
+ *          [
+ *            {"type": value, "data": value },
+ *            ...,
+ *          ],
+ *          ...
+ *        ]
+ *
+ *        Pass null to avoid modifying dataTransfer.
+ * @param {String} [aDropEffect="move"]
+ *        The drop effect to set during the dragstart event, or 'move' if omitted.
+ * @param {Window} [aWindow=window]
+ *        The window in which the drag happens. Defaults to the window in which
+ *        EventUtils.js is loaded.
+ * @param {Window} [aDestWindow=aWindow]
+ *        Used when aDestElement is in a different window than aSrcElement.
+ *        Default is to match ``aWindow``.
+ * @param {Object} [aDragEvent={}]
+ *        Defaults to empty object. Overwrites an object passed to sendDragEvent.
+ * @return {Array}
+ *        A two element array, where the first element is the value returned
+ *        from sendDragEvent for dragover event, and the second element is the
+ *        dataTransfer for the current drag session.
+ */
+function synthesizeDragOver(
+  aSrcElement,
+  aDestElement,
+  aDragData,
+  aDropEffect,
+  aWindow,
+  aDestWindow,
+  aDragEvent = {}
+) {
+  if (!aWindow) {
+    aWindow = window;
+  }
+  if (!aDestWindow) {
+    aDestWindow = aWindow;
+  }
+
+  // eslint-disable-next-line mozilla/use-services
+  const obs = _EU_Cc["@mozilla.org/observer-service;1"].getService(
+    _EU_Ci.nsIObserverService
+  );
+  const ds = _EU_Cc["@mozilla.org/widget/dragservice;1"].getService(
+    _EU_Ci.nsIDragService
+  );
+  var sess = ds.getCurrentSession();
+
+  // This method runs before other callbacks, and acts as a way to inject the
+  // initial drag data into the DataTransfer.
+  function fillDrag(event) {
+    if (aDragData) {
+      for (var i = 0; i < aDragData.length; i++) {
+        var item = aDragData[i];
+        for (var j = 0; j < item.length; j++) {
+          _EU_maybeWrap(event.dataTransfer).mozSetDataAt(
+            item[j].type,
+            item[j].data,
+            i
+          );
+        }
+      }
+    }
+    event.dataTransfer.dropEffect = aDropEffect || "move";
+    event.preventDefault();
+  }
+
+  function trapDrag(subject, topic) {
+    if (topic == "on-datatransfer-available") {
+      sess.dataTransfer = _EU_maybeUnwrap(
+        _EU_maybeWrap(subject).mozCloneForEvent("drop")
+      );
+      sess.dataTransfer.dropEffect = subject.dropEffect;
+    }
+  }
+
+  // need to use real mouse action
+  aWindow.addEventListener("dragstart", fillDrag, true);
+  obs.addObserver(trapDrag, "on-datatransfer-available");
+  synthesizeMouseAtCenter(aSrcElement, { type: "mousedown" }, aWindow);
+
+  var rect = aSrcElement.getBoundingClientRect();
+  var x = rect.width / 2;
+  var y = rect.height / 2;
+  synthesizeMouse(aSrcElement, x, y, { type: "mousemove" }, aWindow);
+  synthesizeMouse(aSrcElement, x + 10, y + 10, { type: "mousemove" }, aWindow);
+  aWindow.removeEventListener("dragstart", fillDrag, true);
+  obs.removeObserver(trapDrag, "on-datatransfer-available");
+
+  var dataTransfer = sess.dataTransfer;
+  if (!dataTransfer) {
+    throw new Error("No data transfer object after synthesizing the mouse!");
+  }
+
+  // The EventStateManager will fire our dragenter event if it needs to.
+  var event = createDragEventObject(
+    "dragover",
+    aDestElement,
+    aDestWindow,
+    dataTransfer,
+    aDragEvent
+  );
+  var result = sendDragEvent(event, aDestElement, aDestWindow);
+
+  return [result, dataTransfer];
+}
+
+/**
+ * Emulate the drop event and mouseup event.
+ * This should be called after synthesizeDragOver.
+ *
+ * @param {*} aResult
+ *        The first element of the array returned from ``synthesizeDragOver``.
+ * @param {DataTransfer} aDataTransfer
+ *        The second element of the array returned from ``synthesizeDragOver``.
+ * @param {Element} aDestElement
+ *        The element on which to fire the drop event.
+ * @param {Window} [aDestWindow=window]
+ *        The window in which the drop happens. Defaults to the window in which
+ *        EventUtils.js is loaded.
+ * @param {Object} [aDragEvent={}]
+ *        Defaults to empty object. Overwrites an object passed to sendDragEvent.
+ * @return {String}
+ *        "none" if aResult is true, ``aDataTransfer.dropEffect`` otherwise.
+ */
+function synthesizeDropAfterDragOver(
+  aResult,
+  aDataTransfer,
+  aDestElement,
+  aDestWindow,
+  aDragEvent = {}
+) {
+  if (!aDestWindow) {
+    aDestWindow = window;
+  }
+
+  var effect = aDataTransfer.dropEffect;
+  var event;
+
+  if (aResult) {
+    effect = "none";
+  } else if (effect != "none") {
+    event = createDragEventObject(
+      "drop",
+      aDestElement,
+      aDestWindow,
+      aDataTransfer,
+      aDragEvent
+    );
+    sendDragEvent(event, aDestElement, aDestWindow);
+  }
+  synthesizeMouse(aDestElement, 2, 2, { type: "mouseup" }, aDestWindow);
+
+  return effect;
+}
+
+/**
+ * Emulate a drag and drop by emulating a dragstart and firing events dragenter,
+ * dragover, and drop.
+ *
+ * @param {Element} aSrcElement
+ *        The element to use to start the drag.
+ * @param {Element} aDestElement
+ *        The element to fire the dragover, dragenter events
+ * @param {Array}   aDragData
+ *        The data to supply for the data transfer.
+ *        This data is in the format:
+ *
+ *            [
+ *              [
+ *                {"type": value, "data": value },
+ *                ...,
+ *              ],
+ *              ...
+ *            ]
+ *
+ *        Pass null to avoid modifying dataTransfer.
+ * @param {String} [aDropEffect="move"]
+ *        The drop effect to set during the dragstart event, or 'move' if omitted..
+ * @param {Window} [aWindow=window]
+ *        The window in which the drag happens. Defaults to the window in which
+ *        EventUtils.js is loaded.
+ * @param {Window} [aDestWindow=aWindow]
+ *        Used when aDestElement is in a different window than aSrcElement.
+ *        Default is to match ``aWindow``.
+ * @param {Object} [aDragEvent={}]
+ *        Defaults to empty object. Overwrites an object passed to sendDragEvent.
+ * @return {String}
+ *        The drop effect that was desired.
+ */
+function synthesizeDrop(
+  aSrcElement,
+  aDestElement,
+  aDragData,
+  aDropEffect,
+  aWindow,
+  aDestWindow,
+  aDragEvent = {}
+) {
+  if (!aWindow) {
+    aWindow = window;
+  }
+  if (!aDestWindow) {
+    aDestWindow = aWindow;
+  }
+
+  var ds = _EU_Cc["@mozilla.org/widget/dragservice;1"].getService(
+    _EU_Ci.nsIDragService
+  );
+
+  let dropAction;
+  switch (aDropEffect) {
+    case null:
+    case undefined:
+    case "move":
+      dropAction = _EU_Ci.nsIDragService.DRAGDROP_ACTION_MOVE;
+      break;
+    case "copy":
+      dropAction = _EU_Ci.nsIDragService.DRAGDROP_ACTION_COPY;
+      break;
+    case "link":
+      dropAction = _EU_Ci.nsIDragService.DRAGDROP_ACTION_LINK;
+      break;
+    default:
+      throw new Error(`${aDropEffect} is an invalid drop effect value`);
+  }
+
+  ds.startDragSessionForTests(dropAction);
+
+  try {
+    var [result, dataTransfer] = synthesizeDragOver(
+      aSrcElement,
+      aDestElement,
+      aDragData,
+      aDropEffect,
+      aWindow,
+      aDestWindow,
+      aDragEvent
+    );
+    return synthesizeDropAfterDragOver(
+      result,
+      dataTransfer,
+      aDestElement,
+      aDestWindow,
+      aDragEvent
+    );
+  } finally {
+    ds.endDragSession(true, _parseModifiers(aDragEvent));
+  }
+}
+
+function _getFlattenedTreeParentNode(aNode) {
+  return _EU_maybeUnwrap(_EU_maybeWrap(aNode).flattenedTreeParentNode);
+}
+
+function _getInclusiveFlattenedTreeParentElement(aNode) {
+  for (
+    let inclusiveAncestor = aNode;
+    inclusiveAncestor;
+    inclusiveAncestor = _getFlattenedTreeParentNode(inclusiveAncestor)
+  ) {
+    if (inclusiveAncestor.nodeType == Node.ELEMENT_NODE) {
+      return inclusiveAncestor;
+    }
+  }
+  return null;
+}
+
+function _nodeIsFlattenedTreeDescendantOf(
+  aPossibleDescendant,
+  aPossibleAncestor
+) {
+  do {
+    if (aPossibleDescendant == aPossibleAncestor) {
+      return true;
+    }
+    aPossibleDescendant = _getFlattenedTreeParentNode(aPossibleDescendant);
+  } while (aPossibleDescendant);
+  return false;
+}
+
+function _computeSrcElementFromSrcSelection(aSrcSelection) {
+  let srcElement = aSrcSelection.focusNode;
+  while (_EU_maybeWrap(srcElement).isNativeAnonymous) {
+    srcElement = _getFlattenedTreeParentNode(srcElement);
+  }
+  if (srcElement.nodeType !== Node.ELEMENT_NODE) {
+    srcElement = _getInclusiveFlattenedTreeParentElement(srcElement);
+  }
+  return srcElement;
+}
+
+/**
+ * Emulate a drag and drop by emulating a dragstart by mousedown and mousemove,
+ * and firing events dragenter, dragover, drop, and dragend.
+ * This does not modify dataTransfer and tries to emulate the plain drag and
+ * drop as much as possible, compared to synthesizeDrop.
+ * Note that if synthesized dragstart is canceled, this throws an exception
+ * because in such case, Gecko does not start drag session.
+ *
+ * @param {Object} aParams
+ * @param {Event} aParams.dragEvent
+ *                The DnD events will be generated with modifiers specified with this.
+ * @param {Element} aParams.srcElement
+ *                The element to start dragging.  If srcSelection is
+ *                set, this is computed for element at focus node.
+ * @param {Selection|nil} aParams.srcSelection
+ *                The selection to start to drag, set null if srcElement is set.
+ * @param {Element|nil} aParams.destElement
+ *                The element to drop on. Pass null to emulate a drop on an invalid target.
+ * @param {Number} aParams.srcX
+ *                The initial x coordinate inside srcElement or ignored if srcSelection is set.
+ * @param {Number} aParams.srcY
+ *                The initial y coordinate inside srcElement or ignored if srcSelection is set.
+ * @param {Number} aParams.stepX
+ *                The x-axis step for mousemove inside srcElement
+ * @param {Number} aParams.stepY
+ *                The y-axis step for mousemove inside srcElement
+ * @param {Number} aParams.finalX
+ *                The final x coordinate inside srcElement
+ * @param {Number} aParams.finalY
+ *                The final x coordinate inside srcElement
+ * @param {Any} aParams.id
+ *                The pointer event id
+ * @param {Window} aParams.srcWindow
+ *                The window for dispatching event on srcElement, defaults to the current window object.
+ * @param {Window} aParams.destWindow
+ *                The window for dispatching event on destElement, defaults to the current window object.
+ * @param {Boolean} aParams.expectCancelDragStart
+ *                Set to true if the test cancels "dragstart"
+ * @param {Boolean} aParams.expectSrcElementDisconnected
+ *                Set to true if srcElement will be disconnected and
+ *                "dragend" event won't be fired.
+ * @param {Function} aParams.logFunc
+ *                Set function which takes one argument if you need to log rect of target.  E.g., `console.log`.
+ */
+// eslint-disable-next-line complexity
+async function synthesizePlainDragAndDrop(aParams) {
+  let {
+    dragEvent = {},
+    srcElement,
+    srcSelection,
+    destElement,
+    srcX = 2,
+    srcY = 2,
+    stepX = 9,
+    stepY = 9,
+    finalX = srcX + stepX * 2,
+    finalY = srcY + stepY * 2,
+    id = _getDOMWindowUtils(window).DEFAULT_MOUSE_POINTER_ID,
+    srcWindow = window,
+    destWindow = window,
+    expectCancelDragStart = false,
+    expectSrcElementDisconnected = false,
+    logFunc,
+  } = aParams;
+  // Don't modify given dragEvent object because we modify dragEvent below and
+  // callers may use the object multiple times so that callers must not assume
+  // that it'll be modified.
+  if (aParams.dragEvent !== undefined) {
+    dragEvent = Object.assign({}, aParams.dragEvent);
+  }
+
+  function rectToString(aRect) {
+    return `left: ${aRect.left}, top: ${aRect.top}, right: ${aRect.right}, bottom: ${aRect.bottom}`;
+  }
+
+  if (logFunc) {
+    logFunc("synthesizePlainDragAndDrop() -- START");
+  }
+
+  if (srcSelection) {
+    srcElement = _computeSrcElementFromSrcSelection(srcSelection);
+    let srcElementRect = srcElement.getBoundingClientRect();
+    if (logFunc) {
+      logFunc(
+        `srcElement.getBoundingClientRect(): ${rectToString(srcElementRect)}`
+      );
+    }
+    // Use last selection client rect because nsIDragSession.sourceNode is
+    // initialized from focus node which is usually in last rect.
+    let selectionRectList = srcSelection.getRangeAt(0).getClientRects();
+    let lastSelectionRect = selectionRectList[selectionRectList.length - 1];
+    if (logFunc) {
+      logFunc(
+        `srcSelection.getRangeAt(0).getClientRects()[${
+          selectionRectList.length - 1
+        }]: ${rectToString(lastSelectionRect)}`
+      );
+    }
+    // Click at center of last selection rect.
+    srcX = Math.floor(lastSelectionRect.left + lastSelectionRect.width / 2);
+    srcY = Math.floor(lastSelectionRect.top + lastSelectionRect.height / 2);
+    // Then, adjust srcX and srcY for making them offset relative to
+    // srcElementRect because they will be used when we call synthesizeMouse()
+    // with srcElement.
+    srcX = Math.floor(srcX - srcElementRect.left);
+    srcY = Math.floor(srcY - srcElementRect.top);
+    // Finally, recalculate finalX and finalY with new srcX and srcY if they
+    // are not specified by the caller.
+    if (aParams.finalX === undefined) {
+      finalX = srcX + stepX * 2;
+    }
+    if (aParams.finalY === undefined) {
+      finalY = srcY + stepY * 2;
+    }
+  } else if (logFunc) {
+    logFunc(
+      `srcElement.getBoundingClientRect(): ${rectToString(
+        srcElement.getBoundingClientRect()
+      )}`
+    );
+  }
+
+  const ds = _EU_Cc["@mozilla.org/widget/dragservice;1"].getService(
+    _EU_Ci.nsIDragService
+  );
+
+  const editingHost = (() => {
+    if (!srcElement.matches(":read-write")) {
+      return null;
+    }
+    let lastEditableElement = srcElement;
+    for (
+      let inclusiveAncestor =
+        _getInclusiveFlattenedTreeParentElement(srcElement);
+      inclusiveAncestor;
+      inclusiveAncestor = _getInclusiveFlattenedTreeParentElement(
+        _getFlattenedTreeParentNode(inclusiveAncestor)
+      )
+    ) {
+      if (inclusiveAncestor.matches(":read-write")) {
+        lastEditableElement = inclusiveAncestor;
+        if (lastEditableElement == srcElement.ownerDocument.body) {
+          break;
+        }
+      }
+    }
+    return lastEditableElement;
+  })();
+  try {
+    _getDOMWindowUtils(srcWindow).disableNonTestMouseEvents(true);
+
+    await new Promise(r => setTimeout(r, 0));
+
+    let mouseDownEvent;
+    function onMouseDown(aEvent) {
+      mouseDownEvent = aEvent;
+      if (logFunc) {
+        logFunc(
+          `"${aEvent.type}" event is fired on ${
+            aEvent.target
+          } (composedTarget: ${_EU_maybeUnwrap(
+            _EU_maybeWrap(aEvent).composedTarget
+          )}`
+        );
+      }
+      if (
+        !_nodeIsFlattenedTreeDescendantOf(
+          _EU_maybeUnwrap(_EU_maybeWrap(aEvent).composedTarget),
+          srcElement
+        )
+      ) {
+        // If srcX and srcY does not point in one of rects in srcElement,
+        // "mousedown" target is not in srcElement.  Such case must not
+        // be expected by this API users so that we should throw an exception
+        // for making debugging easier.
+        throw new Error(
+          'event target of "mousedown" is not srcElement nor its descendant'
+        );
+      }
+    }
+    try {
+      srcWindow.addEventListener("mousedown", onMouseDown, { capture: true });
+      synthesizeMouse(
+        srcElement,
+        srcX,
+        srcY,
+        { type: "mousedown", id },
+        srcWindow
+      );
+      if (logFunc) {
+        logFunc(`mousedown at ${srcX}, ${srcY}`);
+      }
+      if (!mouseDownEvent) {
+        throw new Error('"mousedown" event is not fired');
+      }
+    } finally {
+      srcWindow.removeEventListener("mousedown", onMouseDown, {
+        capture: true,
+      });
+    }
+
+    let dragStartEvent;
+    function onDragStart(aEvent) {
+      dragStartEvent = aEvent;
+      if (logFunc) {
+        logFunc(`"${aEvent.type}" event is fired`);
+      }
+      if (
+        !_nodeIsFlattenedTreeDescendantOf(
+          _EU_maybeUnwrap(_EU_maybeWrap(aEvent).composedTarget),
+          srcElement
+        )
+      ) {
+        // If srcX and srcY does not point in one of rects in srcElement,
+        // "dragstart" target is not in srcElement.  Such case must not
+        // be expected by this API users so that we should throw an exception
+        // for making debugging easier.
+        throw new Error(
+          'event target of "dragstart" is not srcElement nor its descendant'
+        );
+      }
+    }
+    let dragEnterEvent;
+    function onDragEnterGenerated(aEvent) {
+      dragEnterEvent = aEvent;
+    }
+    srcWindow.addEventListener("dragstart", onDragStart, { capture: true });
+    srcWindow.addEventListener("dragenter", onDragEnterGenerated, {
+      capture: true,
+    });
+    try {
+      // Wait for the next event tick after each event dispatch, so that UI
+      // elements (e.g. menu) work like the real user input.
+      await new Promise(r => setTimeout(r, 0));
+
+      srcX += stepX;
+      srcY += stepY;
+      synthesizeMouse(
+        srcElement,
+        srcX,
+        srcY,
+        { type: "mousemove", id },
+        srcWindow
+      );
+      if (logFunc) {
+        logFunc(`first mousemove at ${srcX}, ${srcY}`);
+      }
+
+      await new Promise(r => setTimeout(r, 0));
+
+      srcX += stepX;
+      srcY += stepY;
+      synthesizeMouse(
+        srcElement,
+        srcX,
+        srcY,
+        { type: "mousemove", id },
+        srcWindow
+      );
+      if (logFunc) {
+        logFunc(`second mousemove at ${srcX}, ${srcY}`);
+      }
+
+      await new Promise(r => setTimeout(r, 0));
+
+      if (!dragStartEvent) {
+        throw new Error('"dragstart" event is not fired');
+      }
+    } finally {
+      srcWindow.removeEventListener("dragstart", onDragStart, {
+        capture: true,
+      });
+      srcWindow.removeEventListener("dragenter", onDragEnterGenerated, {
+        capture: true,
+      });
+    }
+
+    let session = ds.getCurrentSession();
+    if (!session) {
+      if (expectCancelDragStart) {
+        synthesizeMouse(
+          srcElement,
+          finalX,
+          finalY,
+          { type: "mouseup", id },
+          srcWindow
+        );
+        return;
+      }
+      throw new Error("drag hasn't been started by the operation");
+    } else if (expectCancelDragStart) {
+      throw new Error("drag has been started by the operation");
+    }
+
+    if (destElement) {
+      if (
+        (srcElement != destElement && !dragEnterEvent) ||
+        destElement != dragEnterEvent.target
+      ) {
+        if (logFunc) {
+          logFunc(
+            `destElement.getBoundingClientRect(): ${rectToString(
+              destElement.getBoundingClientRect()
+            )}`
+          );
+        }
+
+        function onDragEnter(aEvent) {
+          dragEnterEvent = aEvent;
+          if (logFunc) {
+            logFunc(`"${aEvent.type}" event is fired`);
+          }
+          if (aEvent.target != destElement) {
+            throw new Error('event target of "dragenter" is not destElement');
+          }
+        }
+        destWindow.addEventListener("dragenter", onDragEnter, {
+          capture: true,
+        });
+        try {
+          let event = createDragEventObject(
+            "dragenter",
+            destElement,
+            destWindow,
+            null,
+            dragEvent
+          );
+          sendDragEvent(event, destElement, destWindow);
+          if (!dragEnterEvent && !destElement.disabled) {
+            throw new Error('"dragenter" event is not fired');
+          }
+          if (dragEnterEvent && destElement.disabled) {
+            throw new Error(
+              '"dragenter" event should not be fired on disable element'
+            );
+          }
+        } finally {
+          destWindow.removeEventListener("dragenter", onDragEnter, {
+            capture: true,
+          });
+        }
+      }
+
+      let dragOverEvent;
+      function onDragOver(aEvent) {
+        dragOverEvent = aEvent;
+        if (logFunc) {
+          logFunc(`"${aEvent.type}" event is fired`);
+        }
+        if (aEvent.target != destElement) {
+          throw new Error('event target of "dragover" is not destElement');
+        }
+      }
+      destWindow.addEventListener("dragover", onDragOver, { capture: true });
+      try {
+        // dragover and drop are only fired to a valid drop target. If the
+        // destElement parameter is null, this function is being used to
+        // simulate a drag'n'drop over an invalid drop target.
+        let event = createDragEventObject(
+          "dragover",
+          destElement,
+          destWindow,
+          null,
+          dragEvent
+        );
+        sendDragEvent(event, destElement, destWindow);
+        if (!dragOverEvent && !destElement.disabled) {
+          throw new Error('"dragover" event is not fired');
+        }
+        if (dragEnterEvent && destElement.disabled) {
+          throw new Error(
+            '"dragover" event should not be fired on disable element'
+          );
+        }
+      } finally {
+        destWindow.removeEventListener("dragover", onDragOver, {
+          capture: true,
+        });
+      }
+
+      await new Promise(r => setTimeout(r, 0));
+
+      // If there is not accept to drop the data, "drop" event shouldn't be
+      // fired.
+      // XXX nsIDragSession.canDrop is different only on Linux.  It must be
+      //     a bug of gtk/nsDragService since it manages `mCanDrop` by itself.
+      //     Thus, we should use nsIDragSession.dragAction instead.
+      if (session.dragAction != _EU_Ci.nsIDragService.DRAGDROP_ACTION_NONE) {
+        let dropEvent;
+        function onDrop(aEvent) {
+          dropEvent = aEvent;
+          if (logFunc) {
+            logFunc(`"${aEvent.type}" event is fired`);
+          }
+          if (
+            !_nodeIsFlattenedTreeDescendantOf(
+              _EU_maybeUnwrap(_EU_maybeWrap(aEvent).composedTarget),
+              destElement
+            )
+          ) {
+            throw new Error(
+              'event target of "drop" is not destElement nor its descendant'
+            );
+          }
+        }
+        destWindow.addEventListener("drop", onDrop, { capture: true });
+        try {
+          let event = createDragEventObject(
+            "drop",
+            destElement,
+            destWindow,
+            null,
+            dragEvent
+          );
+          sendDragEvent(event, destElement, destWindow);
+          if (!dropEvent && session.canDrop) {
+            throw new Error('"drop" event is not fired');
+          }
+        } finally {
+          destWindow.removeEventListener("drop", onDrop, { capture: true });
+        }
+        return;
+      }
+    }
+
+    // Since we don't synthesize drop event, we need to set drag end point
+    // explicitly for "dragEnd" event which will be fired by
+    // endDragSession().
+    dragEvent.clientX = finalX;
+    dragEvent.clientY = finalY;
+    let event = createDragEventObject(
+      "dragend",
+      destElement || srcElement,
+      destElement ? srcWindow : destWindow,
+      null,
+      dragEvent
+    );
+    session.setDragEndPointForTests(event.screenX, event.screenY);
+  } finally {
+    await new Promise(r => setTimeout(r, 0));
+
+    if (ds.getCurrentSession()) {
+      const sourceNode = ds.sourceNode;
+      let dragEndEvent;
+      function onDragEnd(aEvent) {
+        dragEndEvent = aEvent;
+        if (logFunc) {
+          logFunc(`"${aEvent.type}" event is fired`);
+        }
+        if (
+          !_nodeIsFlattenedTreeDescendantOf(
+            _EU_maybeUnwrap(_EU_maybeWrap(aEvent).composedTarget),
+            srcElement
+          ) &&
+          _EU_maybeUnwrap(_EU_maybeWrap(aEvent).composedTarget) != editingHost
+        ) {
+          throw new Error(
+            'event target of "dragend" is not srcElement nor its descendant'
+          );
+        }
+        if (expectSrcElementDisconnected) {
+          throw new Error(
+            `"dragend" event shouldn't be fired when the source node is disconnected (the source node is ${
+              sourceNode?.isConnected ? "connected" : "null or disconnected"
+            })`
+          );
+        }
+      }
+      srcWindow.addEventListener("dragend", onDragEnd, { capture: true });
+      try {
+        ds.endDragSession(true, _parseModifiers(dragEvent));
+        if (!expectSrcElementDisconnected && !dragEndEvent) {
+          // eslint-disable-next-line no-unsafe-finally
+          throw new Error(
+            `"dragend" event is not fired by nsIDragService.endDragSession()${
+              ds.sourceNode && !ds.sourceNode.isConnected
+                ? "(sourceNode was disconnected)"
+                : ""
+            }`
+          );
+        }
+      } finally {
+        srcWindow.removeEventListener("dragend", onDragEnd, { capture: true });
+      }
+    }
+    _getDOMWindowUtils(srcWindow).disableNonTestMouseEvents(false);
+    if (logFunc) {
+      logFunc("synthesizePlainDragAndDrop() -- END");
+    }
+  }
+}
+
+function _checkDataTransferItems(aDataTransfer, aExpectedDragData) {
+  try {
+    // We must wrap only in plain mochitests, not chrome
+    let dataTransfer = _EU_maybeWrap(aDataTransfer);
+    if (!dataTransfer) {
+      return null;
+    }
+    if (
+      aExpectedDragData == null ||
+      dataTransfer.mozItemCount != aExpectedDragData.length
+    ) {
+      return dataTransfer;
+    }
+    for (let i = 0; i < dataTransfer.mozItemCount; i++) {
+      let dtTypes = dataTransfer.mozTypesAt(i);
+      if (dtTypes.length != aExpectedDragData[i].length) {
+        return dataTransfer;
+      }
+      for (let j = 0; j < dtTypes.length; j++) {
+        if (dtTypes[j] != aExpectedDragData[i][j].type) {
+          return dataTransfer;
+        }
+        let dtData = dataTransfer.mozGetDataAt(dtTypes[j], i);
+        if (aExpectedDragData[i][j].eqTest) {
+          if (
+            !aExpectedDragData[i][j].eqTest(
+              dtData,
+              aExpectedDragData[i][j].data
+            )
+          ) {
+            return dataTransfer;
+          }
+        } else if (aExpectedDragData[i][j].data != dtData) {
+          return dataTransfer;
+        }
+      }
+    }
+  } catch (ex) {
+    return ex;
+  }
+  return true;
+}
+
+/**
+ * This callback type is used with ``synthesizePlainDragAndCancel()``.
+ * It should compare ``actualData`` and ``expectedData`` and return
+ * true if the two should be considered equal, false otherwise.
+ *
+ * @callback eqTest
+ * @param {*} actualData
+ * @param {*} expectedData
+ * @return {boolean}
+ */
+
+/**
+ * synthesizePlainDragAndCancel() synthesizes drag start with
+ * synthesizePlainDragAndDrop(), but always cancel it with preventing default
+ * of "dragstart".  Additionally, this checks whether the dataTransfer of
+ * "dragstart" event has only expected items.
+ *
+ * @param {Object} aParams
+ *        The params which is set to the argument of ``synthesizePlainDragAndDrop()``.
+ * @param {Array} aExpectedDataTransferItems
+ *        All expected dataTransfer items.
+ *        This data is in the format:
+ *
+ *        [
+ *          [
+ *            {"type": value, "data": value, eqTest: function}
+ *            ...,
+ *          ],
+ *          ...
+ *        ]
+ *
+ *        This can also be null.
+ *        You can optionally provide ``eqTest`` {@type eqTest} if the
+ *        comparison to the expected data transfer items can't be done
+ *        with x == y;
+ * @return {boolean}
+ *        true if aExpectedDataTransferItems matches with
+ *        DragEvent.dataTransfer of "dragstart" event.
+ *        Otherwise, the dataTransfer object (may be null) or
+ *        thrown exception, NOT false.  Therefore, you shouldn't
+ *        use.
+ */
+async function synthesizePlainDragAndCancel(
+  aParams,
+  aExpectedDataTransferItems
+) {
+  let srcElement = aParams.srcSelection
+    ? _computeSrcElementFromSrcSelection(aParams.srcSelection)
+    : aParams.srcElement;
+  let result;
+  function onDragStart(aEvent) {
+    aEvent.preventDefault();
+    result = _checkDataTransferItems(
+      aEvent.dataTransfer,
+      aExpectedDataTransferItems
+    );
+  }
+  SpecialPowers.addSystemEventListener(
+    srcElement.ownerDocument,
+    "dragstart",
+    onDragStart,
+    { capture: true }
+  );
+  try {
+    aParams.expectCancelDragStart = true;
+    await synthesizePlainDragAndDrop(aParams);
+  } finally {
+    SpecialPowers.removeSystemEventListener(
+      srcElement.ownerDocument,
+      "dragstart",
+      onDragStart,
+      { capture: true }
+    );
+  }
+  return result;
+}
+
+class EventCounter {
+  constructor(aTarget, aType, aOptions = {}) {
+    this.target = aTarget;
+    this.type = aType;
+    this.options = aOptions;
+
+    this.eventCount = 0;
+    // Bug 1512817:
+    // SpecialPowers is picky and needs to be passed an explicit reference to
+    // the function to be called. To avoid having to bind "this", we therefore
+    // define the method this way, via a property.
+    this.handleEvent = aEvent => {
+      this.eventCount++;
+    };
+
+    if (aOptions.mozSystemGroup) {
+      SpecialPowers.addSystemEventListener(
+        aTarget,
+        aType,
+        this.handleEvent,
+        aOptions.capture
+      );
+    } else {
+      aTarget.addEventListener(aType, this, aOptions);
+    }
+  }
+
+  unregister() {
+    if (this.options.mozSystemGroup) {
+      SpecialPowers.removeSystemEventListener(
+        this.target,
+        this.type,
+        this.handleEvent,
+        this.options.capture
+      );
+    } else {
+      this.target.removeEventListener(this.type, this, this.options);
+    }
+  }
+
+  get count() {
+    return this.eventCount;
+  }
+}
diff --git a/testing/mochitest/tests/SimpleTest/ExtensionTestUtils.js b/testing/mochitest/tests/SimpleTest/ExtensionTestUtils.js
new file mode 100644
index 0000000000..fa86116c92
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/ExtensionTestUtils.js
@@ -0,0 +1,180 @@
+const { ExtensionTestCommon } = SpecialPowers.ChromeUtils.importESModule(
+  "resource://testing-common/ExtensionTestCommon.sys.mjs"
+);
+
+var ExtensionTestUtils = {
+  // Shortcut to more easily access WebExtensionPolicy.backgroundServiceWorkerEnabled
+  // from mochitest-plain tests.
+  getBackgroundServiceWorkerEnabled() {
+    return ExtensionTestCommon.getBackgroundServiceWorkerEnabled();
+  },
+
+  // A test helper used to check if the pref "extension.backgroundServiceWorker.forceInTestExtension"
+  // is set to true.
+  isInBackgroundServiceWorkerTests() {
+    return ExtensionTestCommon.isInBackgroundServiceWorkerTests();
+  },
+
+  get testAssertions() {
+    return ExtensionTestCommon.testAssertions;
+  },
+};
+
+ExtensionTestUtils.loadExtension = function (ext) {
+  // Cleanup functions need to be registered differently depending on
+  // whether we're in browser chrome or plain mochitests.
+  var registerCleanup;
+  /* global registerCleanupFunction */
+  if (typeof registerCleanupFunction != "undefined") {
+    registerCleanup = registerCleanupFunction;
+  } else {
+    registerCleanup = SimpleTest.registerCleanupFunction.bind(SimpleTest);
+  }
+
+  var testResolve;
+  var testDone = new Promise(resolve => {
+    testResolve = resolve;
+  });
+
+  var messageHandler = new Map();
+  var messageAwaiter = new Map();
+
+  var messageQueue = new Set();
+
+  registerCleanup(() => {
+    if (messageQueue.size) {
+      let names = Array.from(messageQueue, ([msg]) => msg);
+      SimpleTest.is(JSON.stringify(names), "[]", "message queue is empty");
+    }
+    if (messageAwaiter.size) {
+      let names = Array.from(messageAwaiter.keys());
+      SimpleTest.is(
+        JSON.stringify(names),
+        "[]",
+        "no tasks awaiting on messages"
+      );
+    }
+  });
+
+  function checkMessages() {
+    for (let message of messageQueue) {
+      let [msg, ...args] = message;
+
+      let listener = messageAwaiter.get(msg);
+      if (listener) {
+        messageQueue.delete(message);
+        messageAwaiter.delete(msg);
+
+        listener.resolve(...args);
+        return;
+      }
+    }
+  }
+
+  function checkDuplicateListeners(msg) {
+    if (messageHandler.has(msg) || messageAwaiter.has(msg)) {
+      throw new Error("only one message handler allowed");
+    }
+  }
+
+  function testHandler(kind, pass, msg, ...args) {
+    if (kind == "test-eq") {
+      let [expected, actual] = args;
+      SimpleTest.ok(pass, `${msg} - Expected: ${expected}, Actual: ${actual}`);
+    } else if (kind == "test-log") {
+      SimpleTest.info(msg);
+    } else if (kind == "test-result") {
+      SimpleTest.ok(pass, msg);
+    }
+  }
+
+  var handler = {
+    async testResult(kind, pass, msg, ...args) {
+      if (kind == "test-done") {
+        SimpleTest.ok(pass, msg);
+        await testResolve(msg);
+      }
+      testHandler(kind, pass, msg, ...args);
+    },
+
+    testMessage(msg, ...args) {
+      var msgHandler = messageHandler.get(msg);
+      if (msgHandler) {
+        msgHandler(...args);
+      } else {
+        messageQueue.add([msg, ...args]);
+        checkMessages();
+      }
+    },
+  };
+
+  // Mimic serialization of functions as done in `Extension.generateXPI` and
+  // `Extension.generateZipFile` because functions are dropped when `ext` object
+  // is sent to the main process via the message manager.
+  ext = Object.assign({}, ext);
+  if (ext.files) {
+    ext.files = Object.assign({}, ext.files);
+    for (let filename of Object.keys(ext.files)) {
+      let file = ext.files[filename];
+      if (typeof file === "function" || Array.isArray(file)) {
+        ext.files[filename] = ExtensionTestCommon.serializeScript(file);
+      }
+    }
+  }
+  if ("background" in ext) {
+    ext.background = ExtensionTestCommon.serializeScript(ext.background);
+  }
+
+  var extension = SpecialPowers.loadExtension(ext, handler);
+
+  registerCleanup(async () => {
+    if (extension.state == "pending" || extension.state == "running") {
+      SimpleTest.ok(false, "Extension left running at test shutdown");
+      await extension.unload();
+    } else if (extension.state == "unloading") {
+      SimpleTest.ok(false, "Extension not fully unloaded at test shutdown");
+    }
+  });
+
+  extension.awaitMessage = msg => {
+    return new Promise(resolve => {
+      checkDuplicateListeners(msg);
+
+      messageAwaiter.set(msg, { resolve });
+      checkMessages();
+    });
+  };
+
+  extension.onMessage = (msg, callback) => {
+    checkDuplicateListeners(msg);
+    messageHandler.set(msg, callback);
+  };
+
+  extension.awaitFinish = msg => {
+    return testDone.then(actual => {
+      if (msg) {
+        SimpleTest.is(actual, msg, "test result correct");
+      }
+      return actual;
+    });
+  };
+
+  SimpleTest.info(`Extension loaded`);
+  return extension;
+};
+
+ExtensionTestUtils.failOnSchemaWarnings = (warningsAsErrors = true) => {
+  let prefName = "extensions.webextensions.warnings-as-errors";
+  let prefPromise = SpecialPowers.setBoolPref(prefName, warningsAsErrors);
+  if (!warningsAsErrors) {
+    let registerCleanup;
+    if (typeof registerCleanupFunction != "undefined") {
+      registerCleanup = registerCleanupFunction;
+    } else {
+      registerCleanup = SimpleTest.registerCleanupFunction.bind(SimpleTest);
+    }
+    registerCleanup(() => SpecialPowers.setBoolPref(prefName, true));
+  }
+  // In mochitests, setBoolPref is async.
+  return prefPromise.then(() => {});
+};
diff --git a/testing/mochitest/tests/SimpleTest/LogController.js b/testing/mochitest/tests/SimpleTest/LogController.js
new file mode 100644
index 0000000000..29580022f8
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/LogController.js
@@ -0,0 +1,96 @@
+/* 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/. */
+
+var LogController = {}; //create the logger object
+
+LogController.counter = 0; //current log message number
+LogController.listeners = [];
+LogController.logLevel = {
+  FATAL: 50,
+  ERROR: 40,
+  WARNING: 30,
+  INFO: 20,
+  DEBUG: 10,
+};
+
+/* set minimum logging level */
+LogController.logLevelAtLeast = function (minLevel) {
+  if (typeof minLevel == "string") {
+    minLevel = LogController.logLevel[minLevel];
+  }
+  return function (msg) {
+    var msgLevel = msg.level;
+    if (typeof msgLevel == "string") {
+      msgLevel = LogController.logLevel[msgLevel];
+    }
+    return msgLevel >= minLevel;
+  };
+};
+
+/* creates the log message with the given level and info */
+LogController.createLogMessage = function (level, info) {
+  var msg = {};
+  msg.num = LogController.counter;
+  msg.level = level;
+  msg.info = info;
+  msg.timestamp = new Date();
+  return msg;
+};
+
+/* helper method to return a sub-array */
+LogController.extend = function (args, skip) {
+  var ret = [];
+  for (var i = skip; i < args.length; i++) {
+    ret.push(args[i]);
+  }
+  return ret;
+};
+
+/* logs message with given level. Currently used locally by log() and error() */
+LogController.logWithLevel = function (level, message /*, ...*/) {
+  var msg = LogController.createLogMessage(
+    level,
+    LogController.extend(arguments, 1)
+  );
+  LogController.dispatchListeners(msg);
+  LogController.counter += 1;
+};
+
+/* log with level INFO */
+LogController.log = function (message /*, ...*/) {
+  LogController.logWithLevel("INFO", message);
+};
+
+/* log with level ERROR */
+LogController.error = function (message /*, ...*/) {
+  LogController.logWithLevel("ERROR", message);
+};
+
+/* send log message to listeners */
+LogController.dispatchListeners = function (msg) {
+  for (var k in LogController.listeners) {
+    var pair = LogController.listeners[k];
+    if (pair.ident != k || (pair[0] && !pair[0](msg))) {
+      continue;
+    }
+    pair[1](msg);
+  }
+};
+
+/* add a listener to this log given an identifier, a filter (can be null) and the listener object */
+LogController.addListener = function (ident, filter, listener) {
+  if (typeof filter == "string") {
+    filter = LogController.logLevelAtLeast(filter);
+  } else if (filter !== null && typeof filter !== "function") {
+    throw new Error("Filter must be a string, a function, or null");
+  }
+  var entry = [filter, listener];
+  entry.ident = ident;
+  LogController.listeners[ident] = entry;
+};
+
+/* remove a listener from this log */
+LogController.removeListener = function (ident) {
+  delete LogController.listeners[ident];
+};
diff --git a/testing/mochitest/tests/SimpleTest/MemoryStats.js b/testing/mochitest/tests/SimpleTest/MemoryStats.js
new file mode 100644
index 0000000000..40548697ea
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/MemoryStats.js
@@ -0,0 +1,131 @@
+/* -*- js-indent-level: 4; indent-tabs-mode: nil -*- */
+/* vim:set ts=4 sw=4 sts=4 et: */
+/* 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/. */
+
+var MemoryStats = {};
+
+/**
+ * Statistics that we want to retrieve and display after every test is
+ * done.  The keys of this table are intended to be identical to the
+ * relevant attributes of nsIMemoryReporterManager.  However, since
+ * nsIMemoryReporterManager doesn't necessarily support all these
+ * statistics in all build configurations, we also use this table to
+ * tell us whether statistics are supported or not.
+ */
+var MEM_STAT_UNKNOWN = 0;
+var MEM_STAT_UNSUPPORTED = 1;
+var MEM_STAT_SUPPORTED = 2;
+
+MemoryStats._hasMemoryStatistics = {};
+MemoryStats._hasMemoryStatistics.vsize = MEM_STAT_UNKNOWN;
+MemoryStats._hasMemoryStatistics.vsizeMaxContiguous = MEM_STAT_UNKNOWN;
+MemoryStats._hasMemoryStatistics.residentFast = MEM_STAT_UNKNOWN;
+MemoryStats._hasMemoryStatistics.heapAllocated = MEM_STAT_UNKNOWN;
+
+MemoryStats._getService = function (className, interfaceName) {
+  var service;
+  try {
+    service = Cc[className].getService(Ci[interfaceName]);
+  } catch (e) {
+    service = SpecialPowers.Cc[className].getService(
+      SpecialPowers.Ci[interfaceName]
+    );
+  }
+  return service;
+};
+
+MemoryStats._nsIFile = function (pathname) {
+  var f;
+  var contractID = "@mozilla.org/file/local;1";
+  try {
+    f = Cc[contractID].createInstance(Ci.nsIFile);
+  } catch (e) {
+    f = SpecialPowers.Cc[contractID].createInstance(SpecialPowers.Ci.nsIFile);
+  }
+  f.initWithPath(pathname);
+  return f;
+};
+
+MemoryStats.constructPathname = function (directory, basename) {
+  var d = MemoryStats._nsIFile(directory);
+  d.append(basename);
+  return d.path;
+};
+
+MemoryStats.dump = function (
+  testNumber,
+  testURL,
+  dumpOutputDirectory,
+  dumpAboutMemory,
+  dumpDMD
+) {
+  // Use dump because treeherder uses --quiet, which drops 'info'
+  // from the structured logger.
+  var info = function (message) {
+    dump(message + "\n");
+  };
+
+  var mrm = MemoryStats._getService(
+    "@mozilla.org/memory-reporter-manager;1",
+    "nsIMemoryReporterManager"
+  );
+  var statMessage = "";
+  for (var stat in MemoryStats._hasMemoryStatistics) {
+    var supported = MemoryStats._hasMemoryStatistics[stat];
+    var firstAccess = false;
+    if (supported == MEM_STAT_UNKNOWN) {
+      firstAccess = true;
+      try {
+        void mrm[stat];
+        supported = MEM_STAT_SUPPORTED;
+      } catch (e) {
+        supported = MEM_STAT_UNSUPPORTED;
+      }
+      MemoryStats._hasMemoryStatistics[stat] = supported;
+    }
+    if (supported == MEM_STAT_SUPPORTED) {
+      var sizeInMB = Math.round(mrm[stat] / (1024 * 1024));
+      statMessage += " | " + stat + " " + sizeInMB + "MB";
+    } else if (firstAccess) {
+      info(
+        "MEMORY STAT " + stat + " not supported in this build configuration."
+      );
+    }
+  }
+  if (statMessage.length) {
+    info("MEMORY STAT" + statMessage);
+  }
+
+  if (dumpAboutMemory) {
+    var basename = "about-memory-" + testNumber + ".json.gz";
+    var dumpfile = MemoryStats.constructPathname(dumpOutputDirectory, basename);
+    info(testURL + " | MEMDUMP-START " + dumpfile);
+    let md = MemoryStats._getService(
+      "@mozilla.org/memory-info-dumper;1",
+      "nsIMemoryInfoDumper"
+    );
+    md.dumpMemoryReportsToNamedFile(
+      dumpfile,
+      function () {
+        info("TEST-INFO | " + testURL + " | MEMDUMP-END");
+      },
+      null,
+      /* anonymize = */ false,
+      /* minimize memory usage = */ false
+    );
+  }
+
+  if (dumpDMD) {
+    let md = MemoryStats._getService(
+      "@mozilla.org/memory-info-dumper;1",
+      "nsIMemoryInfoDumper"
+    );
+    md.dumpMemoryInfoToTempDir(
+      String(testNumber),
+      /* anonymize = */ false,
+      /* minimize memory usage = */ false
+    );
+  }
+};
diff --git a/testing/mochitest/tests/SimpleTest/MockObjects.js b/testing/mochitest/tests/SimpleTest/MockObjects.js
new file mode 100644
index 0000000000..5782707c04
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/MockObjects.js
@@ -0,0 +1,95 @@
+/* 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/. */
+
+/**
+ * Allows registering a mock XPCOM component, that temporarily replaces the
+ *  original one when an object implementing a given ContractID is requested
+ *  using createInstance.
+ *
+ * @param aContractID
+ *        The ContractID of the component to replace, for example
+ *        "@mozilla.org/filepicker;1".
+ *
+ * @param aReplacementCtor
+ *        The constructor function for the JavaScript object that will be
+ *        created every time createInstance is called. This object must
+ *        implement QueryInterface and provide the XPCOM interfaces required by
+ *        the specified ContractID (for example
+ *        Components.interfaces.nsIFilePicker).
+ */
+
+function MockObjectRegisterer(aContractID, aReplacementCtor) {
+  this._contractID = aContractID;
+  this._replacementCtor = aReplacementCtor;
+}
+
+MockObjectRegisterer.prototype = {
+  /**
+   * Replaces the current factory with one that returns a new mock object.
+   *
+   * After register() has been called, it is mandatory to call unregister() to
+   * restore the original component. Usually, you should use a try-catch block
+   * to ensure that unregister() is called.
+   */
+  register: function MOR_register() {
+    if (this._originalCID) {
+      throw new Error("Invalid object state when calling register()");
+    }
+
+    // Define a factory that creates a new object using the given constructor.
+    var isChrome = location.protocol == "chrome:";
+    var providedConstructor = this._replacementCtor;
+    this._mockFactory = {
+      createInstance: function MF_createInstance(aIid) {
+        var inst = new providedConstructor().QueryInterface(aIid);
+        if (!isChrome) {
+          inst = SpecialPowers.wrapCallbackObject(inst);
+        }
+        return inst;
+      },
+    };
+    if (!isChrome) {
+      this._mockFactory = SpecialPowers.wrapCallbackObject(this._mockFactory);
+    }
+
+    var retVal = SpecialPowers.swapFactoryRegistration(
+      null,
+      this._contractID,
+      this._mockFactory
+    );
+    if ("error" in retVal) {
+      throw new Error("ERROR: " + retVal.error);
+    } else {
+      this._originalCID = retVal.originalCID;
+    }
+  },
+
+  /**
+   * Restores the original factory.
+   */
+  unregister: function MOR_unregister() {
+    if (!this._originalCID) {
+      throw new Error("Invalid object state when calling unregister()");
+    }
+
+    // Free references to the mock factory.
+    SpecialPowers.swapFactoryRegistration(this._originalCID, this._contractID);
+
+    // Allow registering a mock factory again later.
+    this._originalCID = null;
+    this._mockFactory = null;
+  },
+
+  // --- Private methods and properties ---
+
+  /**
+   * The factory of the component being replaced.
+   */
+  _originalCID: null,
+
+  /**
+   * The nsIFactory that was automatically generated by this object.
+   */
+  _mockFactory: null,
+};
diff --git a/testing/mochitest/tests/SimpleTest/MozillaLogger.js b/testing/mochitest/tests/SimpleTest/MozillaLogger.js
new file mode 100644
index 0000000000..13ed5bd8f5
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/MozillaLogger.js
@@ -0,0 +1,102 @@
+/**
+ * MozillaLogger, a base class logger that just logs to stdout.
+ */
+
+"use strict";
+
+function formatLogMessage(msg) {
+  return msg.info.join(" ") + "\n";
+}
+
+function importMJS(mjs) {
+  if (typeof ChromeUtils === "object") {
+    return ChromeUtils.importESModule(mjs);
+  }
+  /* globals SpecialPowers */
+  return SpecialPowers.ChromeUtils.importESModule(mjs);
+}
+
+// When running in release builds, we get a fake Components object in
+// web contexts, so we need to check that the Components object is sane,
+// too, not just that it exists.
+let haveComponents =
+  typeof Components === "object" &&
+  typeof Components.Constructor === "function";
+
+let CC = (
+  haveComponents ? Components : SpecialPowers.wrap(SpecialPowers.Components)
+).Constructor;
+
+let ConverterOutputStream = CC(
+  "@mozilla.org/intl/converter-output-stream;1",
+  "nsIConverterOutputStream",
+  "init"
+);
+
+class MozillaLogger {
+  get logCallback() {
+    return msg => {
+      this.log(formatLogMessage(msg));
+    };
+  }
+
+  log(msg) {
+    dump(msg);
+  }
+
+  close() {}
+}
+
+/**
+ * MozillaFileLogger, a log listener that can write to a local file.
+ * intended to be run from chrome space
+ */
+
+/** Init the file logger with the absolute path to the file.
+    It will create and append if the file already exists **/
+class MozillaFileLogger extends MozillaLogger {
+  constructor(aPath) {
+    super();
+
+    const { FileUtils } = importMJS("resource://gre/modules/FileUtils.sys.mjs");
+
+    this._file = FileUtils.File(aPath);
+    this._foStream = FileUtils.openFileOutputStream(
+      this._file,
+      FileUtils.MODE_WRONLY | FileUtils.MODE_CREATE | FileUtils.MODE_APPEND
+    );
+
+    this._converter = ConverterOutputStream(this._foStream, "UTF-8");
+  }
+
+  get logCallback() {
+    return msg => {
+      if (this._converter) {
+        var data = formatLogMessage(msg);
+        this.log(data);
+
+        if (data.includes("SimpleTest FINISH")) {
+          this.close();
+        }
+      }
+    };
+  }
+
+  log(msg) {
+    if (this._converter) {
+      this._converter.writeString(msg);
+    }
+  }
+
+  close() {
+    this._converter.flush();
+    this._converter.close();
+
+    this._foStream = null;
+    this._converter = null;
+    this._file = null;
+  }
+}
+
+this.MozillaLogger = MozillaLogger;
+this.MozillaFileLogger = MozillaFileLogger;
diff --git a/testing/mochitest/tests/SimpleTest/NativeKeyCodes.js b/testing/mochitest/tests/SimpleTest/NativeKeyCodes.js
new file mode 100644
index 0000000000..b256269e71
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/NativeKeyCodes.js
@@ -0,0 +1,369 @@
+/**
+ * This file defines all virtual keycodes for synthesizeNativeKey() of
+ * EventUtils.js and nsIDOMWindowUtils.sendNativeKeyEvent().
+ * These values are defined in each platform's SDK or documents.
+ */
+
+// Windows
+// Windows' native key code values may include scan code value which can be
+// retrieved with |((code & 0xFFFF0000 >> 16)|.  If the value is 0, it will
+// be computed with active keyboard layout automatically.
+// FYI: Don't define scan code here for printable keys, numeric keys and
+//      IME keys because they depend on active keyboard layout.
+// XXX: Although, ABNT C1 key depends on keyboard layout in strictly speaking.
+//      However, computing its scan code from the virtual keycode,
+//      WIN_VK_ABNT_C1, doesn't work fine (computed as 0x0073, "IntlRo").
+//      Therefore, we should specify it here explicitly (it should be 0x0056,
+//      "IntlBackslash").  Fortunately, the key always generates 0x0056 with
+//      any keyboard layouts as far as I've tested.  So, this must be safe to
+//      test new regressions.
+
+const WIN_VK_LBUTTON = 0x00000001;
+const WIN_VK_RBUTTON = 0x00000002;
+const WIN_VK_CANCEL = 0xe0460003;
+const WIN_VK_MBUTTON = 0x00000004;
+const WIN_VK_XBUTTON1 = 0x00000005;
+const WIN_VK_XBUTTON2 = 0x00000006;
+const WIN_VK_BACK = 0x000e0008;
+const WIN_VK_TAB = 0x000f0009;
+const WIN_VK_CLEAR = 0x004c000c;
+const WIN_VK_RETURN = 0x001c000d;
+const WIN_VK_SHIFT = 0x002a0010;
+const WIN_VK_CONTROL = 0x001d0011;
+const WIN_VK_MENU = 0x00380012;
+const WIN_VK_PAUSE = 0x00450013;
+const WIN_VK_CAPITAL = 0x003a0014;
+const WIN_VK_KANA = 0x00000015;
+const WIN_VK_HANGUEL = 0x00000015;
+const WIN_VK_HANGUL = 0x00000015;
+const WIN_VK_JUNJA = 0x00000017;
+const WIN_VK_FINAL = 0x00000018;
+const WIN_VK_HANJA = 0x00000019;
+const WIN_VK_KANJI = 0x00000019;
+const WIN_VK_ESCAPE = 0x0001001b;
+const WIN_VK_CONVERT = 0x0000001c;
+const WIN_VK_NONCONVERT = 0x0000001d;
+const WIN_VK_ACCEPT = 0x0000001e;
+const WIN_VK_MODECHANGE = 0x0000001f;
+const WIN_VK_SPACE = 0x00390020;
+const WIN_VK_PRIOR = 0xe0490021;
+const WIN_VK_NEXT = 0xe0510022;
+const WIN_VK_END = 0xe04f0023;
+const WIN_VK_HOME = 0xe0470024;
+const WIN_VK_LEFT = 0xe04b0025;
+const WIN_VK_UP = 0xe0480026;
+const WIN_VK_RIGHT = 0xe04d0027;
+const WIN_VK_DOWN = 0xe0500028;
+const WIN_VK_SELECT = 0x00000029;
+const WIN_VK_PRINT = 0x0000002a;
+const WIN_VK_EXECUTE = 0x0000002b;
+const WIN_VK_SNAPSHOT = 0xe037002c;
+const WIN_VK_INSERT = 0xe052002d;
+const WIN_VK_DELETE = 0xe053002e;
+const WIN_VK_HELP = 0x0000002f;
+const WIN_VK_0 = 0x00000030;
+const WIN_VK_1 = 0x00000031;
+const WIN_VK_2 = 0x00000032;
+const WIN_VK_3 = 0x00000033;
+const WIN_VK_4 = 0x00000034;
+const WIN_VK_5 = 0x00000035;
+const WIN_VK_6 = 0x00000036;
+const WIN_VK_7 = 0x00000037;
+const WIN_VK_8 = 0x00000038;
+const WIN_VK_9 = 0x00000039;
+const WIN_VK_A = 0x00000041;
+const WIN_VK_B = 0x00000042;
+const WIN_VK_C = 0x00000043;
+const WIN_VK_D = 0x00000044;
+const WIN_VK_E = 0x00000045;
+const WIN_VK_F = 0x00000046;
+const WIN_VK_G = 0x00000047;
+const WIN_VK_H = 0x00000048;
+const WIN_VK_I = 0x00000049;
+const WIN_VK_J = 0x0000004a;
+const WIN_VK_K = 0x0000004b;
+const WIN_VK_L = 0x0000004c;
+const WIN_VK_M = 0x0000004d;
+const WIN_VK_N = 0x0000004e;
+const WIN_VK_O = 0x0000004f;
+const WIN_VK_P = 0x00000050;
+const WIN_VK_Q = 0x00000051;
+const WIN_VK_R = 0x00000052;
+const WIN_VK_S = 0x00000053;
+const WIN_VK_T = 0x00000054;
+const WIN_VK_U = 0x00000055;
+const WIN_VK_V = 0x00000056;
+const WIN_VK_W = 0x00000057;
+const WIN_VK_X = 0x00000058;
+const WIN_VK_Y = 0x00000059;
+const WIN_VK_Z = 0x0000005a;
+const WIN_VK_LWIN = 0xe05b005b;
+const WIN_VK_RWIN = 0xe05c005c;
+const WIN_VK_APPS = 0xe05d005d;
+const WIN_VK_SLEEP = 0x0000005f;
+const WIN_VK_NUMPAD0 = 0x00520060;
+const WIN_VK_NUMPAD1 = 0x004f0061;
+const WIN_VK_NUMPAD2 = 0x00500062;
+const WIN_VK_NUMPAD3 = 0x00510063;
+const WIN_VK_NUMPAD4 = 0x004b0064;
+const WIN_VK_NUMPAD5 = 0x004c0065;
+const WIN_VK_NUMPAD6 = 0x004d0066;
+const WIN_VK_NUMPAD7 = 0x00470067;
+const WIN_VK_NUMPAD8 = 0x00480068;
+const WIN_VK_NUMPAD9 = 0x00490069;
+const WIN_VK_MULTIPLY = 0x0037006a;
+const WIN_VK_ADD = 0x004e006b;
+const WIN_VK_SEPARATOR = 0x0000006c;
+const WIN_VK_OEM_NEC_SEPARATE = 0x0000006c;
+const WIN_VK_SUBTRACT = 0x004a006d;
+const WIN_VK_DECIMAL = 0x0053006e;
+const WIN_VK_DIVIDE = 0xe035006f;
+const WIN_VK_F1 = 0x003b0070;
+const WIN_VK_F2 = 0x003c0071;
+const WIN_VK_F3 = 0x003d0072;
+const WIN_VK_F4 = 0x003e0073;
+const WIN_VK_F5 = 0x003f0074;
+const WIN_VK_F6 = 0x00400075;
+const WIN_VK_F7 = 0x00410076;
+const WIN_VK_F8 = 0x00420077;
+const WIN_VK_F9 = 0x00430078;
+const WIN_VK_F10 = 0x00440079;
+const WIN_VK_F11 = 0x0057007a;
+const WIN_VK_F12 = 0x0058007b;
+const WIN_VK_F13 = 0x0064007c;
+const WIN_VK_F14 = 0x0065007d;
+const WIN_VK_F15 = 0x0066007e;
+const WIN_VK_F16 = 0x0067007f;
+const WIN_VK_F17 = 0x00680080;
+const WIN_VK_F18 = 0x00690081;
+const WIN_VK_F19 = 0x006a0082;
+const WIN_VK_F20 = 0x006b0083;
+const WIN_VK_F21 = 0x006c0084;
+const WIN_VK_F22 = 0x006d0085;
+const WIN_VK_F23 = 0x006e0086;
+const WIN_VK_F24 = 0x00760087;
+const WIN_VK_NUMLOCK = 0xe0450090;
+const WIN_VK_SCROLL = 0x00460091;
+const WIN_VK_OEM_FJ_JISHO = 0x00000092;
+const WIN_VK_OEM_NEC_EQUAL = 0x00000092;
+const WIN_VK_OEM_FJ_MASSHOU = 0x00000093;
+const WIN_VK_OEM_FJ_TOUROKU = 0x00000094;
+const WIN_VK_OEM_FJ_LOYA = 0x00000095;
+const WIN_VK_OEM_FJ_ROYA = 0x00000096;
+const WIN_VK_LSHIFT = 0x002a00a0;
+const WIN_VK_RSHIFT = 0x003600a1;
+const WIN_VK_LCONTROL = 0x001d00a2;
+const WIN_VK_RCONTROL = 0xe01d00a3;
+const WIN_VK_LMENU = 0x003800a4;
+const WIN_VK_RMENU = 0xe03800a5;
+const WIN_VK_BROWSER_BACK = 0xe06a00a6;
+const WIN_VK_BROWSER_FORWARD = 0xe06900a7;
+const WIN_VK_BROWSER_REFRESH = 0xe06700a8;
+const WIN_VK_BROWSER_STOP = 0xe06800a9;
+const WIN_VK_BROWSER_SEARCH = 0x000000aa;
+const WIN_VK_BROWSER_FAVORITES = 0xe06600ab;
+const WIN_VK_BROWSER_HOME = 0xe03200ac;
+const WIN_VK_VOLUME_MUTE = 0xe02000ad;
+const WIN_VK_VOLUME_DOWN = 0xe02e00ae;
+const WIN_VK_VOLUME_UP = 0xe03000af;
+const WIN_VK_MEDIA_NEXT_TRACK = 0xe01900b0;
+const WIN_VK_OEM_FJ_000 = 0x000000b0;
+const WIN_VK_MEDIA_PREV_TRACK = 0xe01000b1;
+const WIN_VK_OEM_FJ_EUQAL = 0x000000b1;
+const WIN_VK_MEDIA_STOP = 0xe02400b2;
+const WIN_VK_MEDIA_PLAY_PAUSE = 0xe02200b3;
+const WIN_VK_OEM_FJ_00 = 0x000000b3;
+const WIN_VK_LAUNCH_MAIL = 0xe06c00b4;
+const WIN_VK_LAUNCH_MEDIA_SELECT = 0xe06d00b5;
+const WIN_VK_LAUNCH_APP1 = 0xe06b00b6;
+const WIN_VK_LAUNCH_APP2 = 0xe02100b7;
+const WIN_VK_OEM_1 = 0x000000ba;
+const WIN_VK_OEM_PLUS = 0x000000bb;
+const WIN_VK_OEM_COMMA = 0x000000bc;
+const WIN_VK_OEM_MINUS = 0x000000bd;
+const WIN_VK_OEM_PERIOD = 0x000000be;
+const WIN_VK_OEM_2 = 0x000000bf;
+const WIN_VK_OEM_3 = 0x000000c0;
+const WIN_VK_ABNT_C1 = 0x005600c1;
+const WIN_VK_ABNT_C2 = 0x000000c2;
+const WIN_VK_OEM_4 = 0x000000db;
+const WIN_VK_OEM_5 = 0x000000dc;
+const WIN_VK_OEM_6 = 0x000000dd;
+const WIN_VK_OEM_7 = 0x000000de;
+const WIN_VK_OEM_8 = 0x000000df;
+const WIN_VK_OEM_NEC_DP1 = 0x000000e0;
+const WIN_VK_OEM_AX = 0x000000e1;
+const WIN_VK_OEM_NEC_DP2 = 0x000000e1;
+const WIN_VK_OEM_102 = 0x000000e2;
+const WIN_VK_OEM_NEC_DP3 = 0x000000e2;
+const WIN_VK_ICO_HELP = 0x000000e3;
+const WIN_VK_OEM_NEC_DP4 = 0x000000e3;
+const WIN_VK_ICO_00 = 0x000000e4;
+const WIN_VK_PROCESSKEY = 0x000000e5;
+const WIN_VK_ICO_CLEAR = 0x000000e6;
+const WIN_VK_PACKET = 0x000000e7;
+const WIN_VK_ERICSSON_BASE = 0x000000e8;
+const WIN_VK_OEM_RESET = 0x000000e9;
+const WIN_VK_OEM_JUMP = 0x000000ea;
+const WIN_VK_OEM_PA1 = 0x000000eb;
+const WIN_VK_OEM_PA2 = 0x000000ec;
+const WIN_VK_OEM_PA3 = 0x000000ed;
+const WIN_VK_OEM_WSCTRL = 0x000000ee;
+const WIN_VK_OEM_CUSEL = 0x000000ef;
+const WIN_VK_OEM_ATTN = 0x000000f0;
+const WIN_VK_OEM_FINISH = 0x000000f1;
+const WIN_VK_OEM_COPY = 0x000000f2;
+const WIN_VK_OEM_AUTO = 0x000000f3;
+const WIN_VK_OEM_ENLW = 0x000000f4;
+const WIN_VK_OEM_BACKTAB = 0x000000f5;
+const WIN_VK_ATTN = 0x000000f6;
+const WIN_VK_CRSEL = 0x000000f7;
+const WIN_VK_EXSEL = 0x000000f8;
+const WIN_VK_EREOF = 0x000000f9;
+const WIN_VK_PLAY = 0x000000fa;
+const WIN_VK_ZOOM = 0x000000fb;
+const WIN_VK_NONAME = 0x000000fc;
+const WIN_VK_PA1 = 0x000000fd;
+const WIN_VK_OEM_CLEAR = 0x000000fe;
+
+const WIN_VK_NUMPAD_RETURN = 0xe01c000d;
+const WIN_VK_NUMPAD_PRIOR = 0x00490021;
+const WIN_VK_NUMPAD_NEXT = 0x00510022;
+const WIN_VK_NUMPAD_END = 0x004f0023;
+const WIN_VK_NUMPAD_HOME = 0x00470024;
+const WIN_VK_NUMPAD_LEFT = 0x004b0025;
+const WIN_VK_NUMPAD_UP = 0x00480026;
+const WIN_VK_NUMPAD_RIGHT = 0x004d0027;
+const WIN_VK_NUMPAD_DOWN = 0x00500028;
+const WIN_VK_NUMPAD_INSERT = 0x0052002d;
+const WIN_VK_NUMPAD_DELETE = 0x0053002e;
+
+// Mac
+
+const MAC_VK_ANSI_A = 0x00;
+const MAC_VK_ANSI_S = 0x01;
+const MAC_VK_ANSI_D = 0x02;
+const MAC_VK_ANSI_F = 0x03;
+const MAC_VK_ANSI_H = 0x04;
+const MAC_VK_ANSI_G = 0x05;
+const MAC_VK_ANSI_Z = 0x06;
+const MAC_VK_ANSI_X = 0x07;
+const MAC_VK_ANSI_C = 0x08;
+const MAC_VK_ANSI_V = 0x09;
+const MAC_VK_ISO_Section = 0x0a;
+const MAC_VK_ANSI_B = 0x0b;
+const MAC_VK_ANSI_Q = 0x0c;
+const MAC_VK_ANSI_W = 0x0d;
+const MAC_VK_ANSI_E = 0x0e;
+const MAC_VK_ANSI_R = 0x0f;
+const MAC_VK_ANSI_Y = 0x10;
+const MAC_VK_ANSI_T = 0x11;
+const MAC_VK_ANSI_1 = 0x12;
+const MAC_VK_ANSI_2 = 0x13;
+const MAC_VK_ANSI_3 = 0x14;
+const MAC_VK_ANSI_4 = 0x15;
+const MAC_VK_ANSI_6 = 0x16;
+const MAC_VK_ANSI_5 = 0x17;
+const MAC_VK_ANSI_Equal = 0x18;
+const MAC_VK_ANSI_9 = 0x19;
+const MAC_VK_ANSI_7 = 0x1a;
+const MAC_VK_ANSI_Minus = 0x1b;
+const MAC_VK_ANSI_8 = 0x1c;
+const MAC_VK_ANSI_0 = 0x1d;
+const MAC_VK_ANSI_RightBracket = 0x1e;
+const MAC_VK_ANSI_O = 0x1f;
+const MAC_VK_ANSI_U = 0x20;
+const MAC_VK_ANSI_LeftBracket = 0x21;
+const MAC_VK_ANSI_I = 0x22;
+const MAC_VK_ANSI_P = 0x23;
+const MAC_VK_Return = 0x24;
+const MAC_VK_ANSI_L = 0x25;
+const MAC_VK_ANSI_J = 0x26;
+const MAC_VK_ANSI_Quote = 0x27;
+const MAC_VK_ANSI_K = 0x28;
+const MAC_VK_ANSI_Semicolon = 0x29;
+const MAC_VK_ANSI_Backslash = 0x2a;
+const MAC_VK_ANSI_Comma = 0x2b;
+const MAC_VK_ANSI_Slash = 0x2c;
+const MAC_VK_ANSI_N = 0x2d;
+const MAC_VK_ANSI_M = 0x2e;
+const MAC_VK_ANSI_Period = 0x2f;
+const MAC_VK_Tab = 0x30;
+const MAC_VK_Space = 0x31;
+const MAC_VK_ANSI_Grave = 0x32;
+const MAC_VK_Delete = 0x33;
+const MAC_VK_PC_Backspace = 0x33;
+const MAC_VK_Powerbook_KeypadEnter = 0x34;
+const MAC_VK_Escape = 0x35;
+const MAC_VK_RightCommand = 0x36;
+const MAC_VK_Command = 0x37;
+const MAC_VK_Shift = 0x38;
+const MAC_VK_CapsLock = 0x39;
+const MAC_VK_Option = 0x3a;
+const MAC_VK_Control = 0x3b;
+const MAC_VK_RightShift = 0x3c;
+const MAC_VK_RightOption = 0x3d;
+const MAC_VK_RightControl = 0x3e;
+const MAC_VK_Function = 0x3f;
+const MAC_VK_F17 = 0x40;
+const MAC_VK_ANSI_KeypadDecimal = 0x41;
+const MAC_VK_ANSI_KeypadMultiply = 0x43;
+const MAC_VK_ANSI_KeypadPlus = 0x45;
+const MAC_VK_ANSI_KeypadClear = 0x47;
+const MAC_VK_VolumeUp = 0x48;
+const MAC_VK_VolumeDown = 0x49;
+const MAC_VK_Mute = 0x4a;
+const MAC_VK_ANSI_KeypadDivide = 0x4b;
+const MAC_VK_ANSI_KeypadEnter = 0x4c;
+const MAC_VK_ANSI_KeypadMinus = 0x4e;
+const MAC_VK_F18 = 0x4f;
+const MAC_VK_F19 = 0x50;
+const MAC_VK_ANSI_KeypadEquals = 0x51;
+const MAC_VK_ANSI_Keypad0 = 0x52;
+const MAC_VK_ANSI_Keypad1 = 0x53;
+const MAC_VK_ANSI_Keypad2 = 0x54;
+const MAC_VK_ANSI_Keypad3 = 0x55;
+const MAC_VK_ANSI_Keypad4 = 0x56;
+const MAC_VK_ANSI_Keypad5 = 0x57;
+const MAC_VK_ANSI_Keypad6 = 0x58;
+const MAC_VK_ANSI_Keypad7 = 0x59;
+const MAC_VK_F20 = 0x5a;
+const MAC_VK_ANSI_Keypad8 = 0x5b;
+const MAC_VK_ANSI_Keypad9 = 0x5c;
+const MAC_VK_JIS_Yen = 0x5d;
+const MAC_VK_JIS_Underscore = 0x5e;
+const MAC_VK_JIS_KeypadComma = 0x5f;
+const MAC_VK_F5 = 0x60;
+const MAC_VK_F6 = 0x61;
+const MAC_VK_F7 = 0x62;
+const MAC_VK_F3 = 0x63;
+const MAC_VK_F8 = 0x64;
+const MAC_VK_F9 = 0x65;
+const MAC_VK_JIS_Eisu = 0x66;
+const MAC_VK_F11 = 0x67;
+const MAC_VK_JIS_Kana = 0x68;
+const MAC_VK_F13 = 0x69;
+const MAC_VK_PC_PrintScreen = 0x69;
+const MAC_VK_F16 = 0x6a;
+const MAC_VK_F14 = 0x6b;
+const MAC_VK_PC_ScrollLock = 0x6b;
+const MAC_VK_F10 = 0x6d;
+const MAC_VK_PC_ContextMenu = 0x6e;
+const MAC_VK_F12 = 0x6f;
+const MAC_VK_F15 = 0x71;
+const MAC_VK_PC_Pause = 0x71;
+const MAC_VK_Help = 0x72;
+const MAC_VK_PC_Insert = 0x72;
+const MAC_VK_Home = 0x73;
+const MAC_VK_PageUp = 0x74;
+const MAC_VK_ForwardDelete = 0x75;
+const MAC_VK_PC_Delete = 0x75;
+const MAC_VK_F4 = 0x76;
+const MAC_VK_End = 0x77;
+const MAC_VK_F2 = 0x78;
+const MAC_VK_PageDown = 0x79;
+const MAC_VK_F1 = 0x7a;
+const MAC_VK_LeftArrow = 0x7b;
+const MAC_VK_RightArrow = 0x7c;
+const MAC_VK_DownArrow = 0x7d;
+const MAC_VK_UpArrow = 0x7e;
diff --git a/testing/mochitest/tests/SimpleTest/SimpleTest.js b/testing/mochitest/tests/SimpleTest/SimpleTest.js
new file mode 100644
index 0000000000..a5d7528bbc
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/SimpleTest.js
@@ -0,0 +1,2216 @@
+/* -*- js-indent-level: 2; tab-width: 2; indent-tabs-mode: nil -*- */
+/* vim:set ts=2 sw=2 sts=2 et: */
+
+// Generally gTestPath should be set by the harness.
+/* global gTestPath */
+
+/**
+ * SimpleTest framework object.
+ * @class
+ */
+var SimpleTest = {};
+var parentRunner = null;
+
+// Using a try/catch rather than SpecialPowers.Cu.isRemoteProxy() because
+// it doesn't cover the case where an iframe is xorigin but fission is
+// not enabled.
+let isSameOrigin = function (w) {
+  try {
+    w.top.TestRunner;
+  } catch (e) {
+    if (e instanceof DOMException) {
+      return false;
+    }
+  }
+  return true;
+};
+let isXOrigin = !isSameOrigin(window);
+
+// Note: duplicated in browser-test.js . See also bug 1820150.
+function isErrorOrException(err) {
+  // It'd be nice if we had either `Error.isError(err)` or `Error.isInstance(err)`
+  // but we don't, so do it ourselves:
+  if (!err) {
+    return false;
+  }
+  if (err instanceof Ci.nsIException) {
+    return true;
+  }
+  try {
+    let glob = SpecialPowers.Cu.getGlobalForObject(err);
+    return err instanceof glob.Error;
+  } catch {
+    // getGlobalForObject can be upset if it doesn't get passed an object.
+    // Just do a standard instanceof check using this global and cross fingers:
+  }
+  return err instanceof Error;
+}
+
+// In normal test runs, the window that has a TestRunner in its parent is
+// the primary window.  In single test runs, if there is no parent and there
+// is no opener then it is the primary window.
+var isSingleTestRun =
+  parent == window &&
+  !(opener || (window.arguments && window.arguments[0].SimpleTest));
+try {
+  var isPrimaryTestWindow =
+    (isXOrigin && parent != window && parent == top) ||
+    (!isXOrigin && (!!parent.TestRunner || isSingleTestRun));
+} catch (e) {
+  dump(
+    "TEST-UNEXPECTED-FAIL, Exception caught: " +
+      e.message +
+      ", at: " +
+      e.fileName +
+      " (" +
+      e.lineNumber +
+      "), location: " +
+      window.location.href +
+      "\n"
+  );
+}
+
+let xOriginRunner = {
+  init(harnessWindow) {
+    this.harnessWindow = harnessWindow;
+    let url = new URL(document.URL);
+    this.testFile = url.pathname;
+    this.showTestReport = url.searchParams.get("showTestReport") == "true";
+    this.expected = url.searchParams.get("expected");
+  },
+  callHarnessMethod(applyOn, command, ...params) {
+    // Message handled by xOriginTestRunnerHandler in TestRunner.js
+    this.harnessWindow.postMessage(
+      {
+        harnessType: "SimpleTest",
+        applyOn,
+        command,
+        params,
+      },
+      "*"
+    );
+  },
+  getParameterInfo() {
+    let url = new URL(document.URL);
+    return {
+      currentTestURL: url.searchParams.get("currentTestURL"),
+      testRoot: url.searchParams.get("testRoot"),
+    };
+  },
+  addFailedTest(test) {
+    this.callHarnessMethod("runner", "addFailedTest", test);
+  },
+  expectAssertions(min, max) {
+    this.callHarnessMethod("runner", "expectAssertions", min, max);
+  },
+  expectChildProcessCrash() {
+    this.callHarnessMethod("runner", "expectChildProcessCrash");
+  },
+  requestLongerTimeout(factor) {
+    this.callHarnessMethod("runner", "requestLongerTimeout", factor);
+  },
+  _lastAssertionCount: 0,
+  testFinished(tests) {
+    var newAssertionCount = SpecialPowers.assertionCount();
+    var numAsserts = newAssertionCount - this._lastAssertionCount;
+    this._lastAssertionCount = newAssertionCount;
+    this.callHarnessMethod("runner", "addAssertionCount", numAsserts);
+    this.callHarnessMethod("runner", "testFinished", tests);
+  },
+  structuredLogger: {
+    info(msg) {
+      xOriginRunner.callHarnessMethod("logger", "structuredLogger.info", msg);
+    },
+    warning(msg) {
+      xOriginRunner.callHarnessMethod(
+        "logger",
+        "structuredLogger.warning",
+        msg
+      );
+    },
+    error(msg) {
+      xOriginRunner.callHarnessMethod("logger", "structuredLogger.error", msg);
+    },
+    activateBuffering() {
+      xOriginRunner.callHarnessMethod(
+        "logger",
+        "structuredLogger.activateBuffering"
+      );
+    },
+    deactivateBuffering() {
+      xOriginRunner.callHarnessMethod(
+        "logger",
+        "structuredLogger.deactivateBuffering"
+      );
+    },
+    testStatus(url, subtest, status, expected, diagnostic, stack) {
+      xOriginRunner.callHarnessMethod(
+        "logger",
+        "structuredLogger.testStatus",
+        url,
+        subtest,
+        status,
+        expected,
+        diagnostic,
+        stack
+      );
+    },
+  },
+};
+
+// Finds the TestRunner for this test run and the SpecialPowers object (in
+// case it is not defined) from a parent/opener window.
+//
+// Finding the SpecialPowers object is needed when we have ChromePowers in
+// harness.xhtml and we need SpecialPowers in the iframe, and also for tests
+// like test_focus.xhtml where we open a window which opens another window which
+// includes SimpleTest.js.
+(function () {
+  function ancestor(w) {
+    return w.parent != w
+      ? w.parent
+      : w.opener ||
+          (!isXOrigin &&
+            w.arguments &&
+            SpecialPowers.wrap(Window).isInstance(w.arguments[0]) &&
+            w.arguments[0]);
+  }
+
+  var w = ancestor(window);
+  while (w && !parentRunner) {
+    isXOrigin = !isSameOrigin(w);
+
+    if (isXOrigin) {
+      if (w.parent != w) {
+        w = w.top;
+      }
+      xOriginRunner.init(w);
+      parentRunner = xOriginRunner;
+    }
+
+    if (!parentRunner) {
+      parentRunner = w.TestRunner;
+      if (!parentRunner && w.wrappedJSObject) {
+        parentRunner = w.wrappedJSObject.TestRunner;
+      }
+    }
+    w = ancestor(w);
+  }
+
+  if (parentRunner) {
+    SimpleTest.harnessParameters = parentRunner.getParameterInfo();
+  }
+})();
+
+/* Helper functions pulled out of various MochiKit modules */
+if (typeof repr == "undefined") {
+  this.repr = function repr(o) {
+    if (typeof o == "undefined") {
+      return "undefined";
+    } else if (o === null) {
+      return "null";
+    }
+    try {
+      if (typeof o.__repr__ == "function") {
+        return o.__repr__();
+      } else if (typeof o.repr == "function" && o.repr != repr) {
+        return o.repr();
+      }
+    } catch (e) {}
+    try {
+      if (
+        typeof o.NAME == "string" &&
+        (o.toString == Function.prototype.toString ||
+          o.toString == Object.prototype.toString)
+      ) {
+        return o.NAME;
+      }
+    } catch (e) {}
+    var ostring;
+    try {
+      if (o === 0) {
+        ostring = 1 / o > 0 ? "+0" : "-0";
+      } else if (typeof o === "string") {
+        ostring = JSON.stringify(o);
+      } else if (Array.isArray(o)) {
+        ostring = "[" + o.map(val => repr(val)).join(", ") + "]";
+      } else {
+        ostring = o + "";
+      }
+    } catch (e) {
+      return "[" + typeof o + "]";
+    }
+    if (typeof o == "function") {
+      o = ostring.replace(/^\s+/, "");
+      var idx = o.indexOf("{");
+      if (idx != -1) {
+        o = o.substr(0, idx) + "{...}";
+      }
+    }
+    return ostring;
+  };
+}
+
+/* This returns a function that applies the previously given parameters.
+ * This is used by SimpleTest.showReport
+ */
+if (typeof partial == "undefined") {
+  this.partial = function (func) {
+    var args = [];
+    for (let i = 1; i < arguments.length; i++) {
+      args.push(arguments[i]);
+    }
+    return function () {
+      if (arguments.length) {
+        for (let i = 1; i < arguments.length; i++) {
+          args.push(arguments[i]);
+        }
+      }
+      func(args);
+    };
+  };
+}
+
+if (typeof getElement == "undefined") {
+  this.getElement = function (id) {
+    return typeof id == "string" ? document.getElementById(id) : id;
+  };
+  this.$ = this.getElement;
+}
+
+SimpleTest._newCallStack = function (path) {
+  var rval = function callStackHandler() {
+    var callStack = callStackHandler.callStack;
+    for (var i = 0; i < callStack.length; i++) {
+      if (callStack[i].apply(this, arguments) === false) {
+        break;
+      }
+    }
+    try {
+      this[path] = null;
+    } catch (e) {
+      // pass
+    }
+  };
+  rval.callStack = [];
+  return rval;
+};
+
+if (typeof addLoadEvent == "undefined") {
+  this.addLoadEvent = function (func) {
+    var existing = window.onload;
+    var regfunc = existing;
+    if (
+      !(
+        typeof existing == "function" &&
+        typeof existing.callStack == "object" &&
+        existing.callStack !== null
+      )
+    ) {
+      regfunc = SimpleTest._newCallStack("onload");
+      if (typeof existing == "function") {
+        regfunc.callStack.push(existing);
+      }
+      window.onload = regfunc;
+    }
+    regfunc.callStack.push(func);
+  };
+}
+
+function createEl(type, attrs, html) {
+  //use createElementNS so the xul/xhtml tests have no issues
+  var el;
+  if (!document.body) {
+    el = document.createElementNS("http://www.w3.org/1999/xhtml", type);
+  } else {
+    el = document.createElement(type);
+  }
+  if (attrs !== null && attrs !== undefined) {
+    for (var k in attrs) {
+      el.setAttribute(k, attrs[k]);
+    }
+  }
+  if (html !== null && html !== undefined) {
+    el.appendChild(document.createTextNode(html));
+  }
+  return el;
+}
+
+/* lots of tests use this as a helper to get css properties */
+if (typeof computedStyle == "undefined") {
+  this.computedStyle = function (elem, cssProperty) {
+    elem = getElement(elem);
+    if (elem.currentStyle) {
+      return elem.currentStyle[cssProperty];
+    }
+    if (typeof document.defaultView == "undefined" || document === null) {
+      return undefined;
+    }
+    var style = document.defaultView.getComputedStyle(elem);
+    if (typeof style == "undefined" || style === null) {
+      return undefined;
+    }
+
+    var selectorCase = cssProperty.replace(/([A-Z])/g, "-$1").toLowerCase();
+
+    return style.getPropertyValue(selectorCase);
+  };
+}
+
+SimpleTest._tests = [];
+SimpleTest._stopOnLoad = true;
+SimpleTest._cleanupFunctions = [];
+SimpleTest._timeoutFunctions = [];
+SimpleTest._inChaosMode = false;
+// When using failure pattern file to filter unexpected issues,
+// SimpleTest.expected would be an array of [pattern, expected count],
+// and SimpleTest.num_failed would be an array of actual counts which
+// has the same length as SimpleTest.expected.
+SimpleTest.expected = "pass";
+SimpleTest.num_failed = 0;
+
+SpecialPowers.setAsDefaultAssertHandler();
+
+function usesFailurePatterns() {
+  return Array.isArray(SimpleTest.expected);
+}
+
+/**
+ * Checks whether there is any failure pattern matches the given error
+ * message, and if found, bumps the counter of the failure pattern.
+ *
+ * @return {boolean} Whether a matched failure pattern is found.
+ */
+function recordIfMatchesFailurePattern(name, diag) {
+  let index = SimpleTest.expected.findIndex(([pat, count]) => {
+    return (
+      pat == null ||
+      (typeof name == "string" && name.includes(pat)) ||
+      (typeof diag == "string" && diag.includes(pat))
+    );
+  });
+  if (index >= 0) {
+    SimpleTest.num_failed[index]++;
+    return true;
+  }
+  return false;
+}
+
+SimpleTest.setExpected = function () {
+  if (!parentRunner) {
+    return;
+  }
+  if (!Array.isArray(parentRunner.expected)) {
+    SimpleTest.expected = parentRunner.expected;
+  } else {
+    // Assertions are checked by the runner.
+    SimpleTest.expected = parentRunner.expected.filter(
+      ([pat]) => pat != "ASSERTION"
+    );
+    SimpleTest.num_failed = new Array(SimpleTest.expected.length);
+    SimpleTest.num_failed.fill(0);
+  }
+};
+SimpleTest.setExpected();
+
+/**
+ * Something like assert.
+ **/
+SimpleTest.ok = function (condition, name) {
+  if (arguments.length > 2) {
+    const diag = "Too many arguments passed to `ok(condition, name)`";
+    SimpleTest.record(false, name, diag);
+  } else {
+    SimpleTest.record(condition, name);
+  }
+};
+
+SimpleTest.record = function (condition, name, diag, stack, expected) {
+  var test = { result: !!condition, name, diag };
+  let successInfo;
+  let failureInfo;
+  if (SimpleTest.expected == "fail") {
+    if (!test.result) {
+      SimpleTest.num_failed++;
+      test.result = true;
+    }
+    successInfo = {
+      status: "PASS",
+      expected: "PASS",
+      message: "TEST-PASS",
+    };
+    failureInfo = {
+      status: "FAIL",
+      expected: "FAIL",
+      message: "TEST-KNOWN-FAIL",
+    };
+  } else if (!test.result && usesFailurePatterns()) {
+    if (recordIfMatchesFailurePattern(name, diag)) {
+      test.result = true;
+      // Add a mark for unexpected failures suppressed by failure pattern.
+      name = "[suppressed] " + name;
+    }
+    successInfo = {
+      status: "FAIL",
+      expected: "FAIL",
+      message: "TEST-KNOWN-FAIL",
+    };
+    failureInfo = {
+      status: "FAIL",
+      expected: "PASS",
+      message: "TEST-UNEXPECTED-FAIL",
+    };
+  } else if (expected == "fail") {
+    successInfo = {
+      status: "PASS",
+      expected: "FAIL",
+      message: "TEST-UNEXPECTED-PASS",
+    };
+    failureInfo = {
+      status: "FAIL",
+      expected: "FAIL",
+      message: "TEST-KNOWN-FAIL",
+    };
+  } else {
+    successInfo = {
+      status: "PASS",
+      expected: "PASS",
+      message: "TEST-PASS",
+    };
+    failureInfo = {
+      status: "FAIL",
+      expected: "PASS",
+      message: "TEST-UNEXPECTED-FAIL",
+    };
+  }
+
+  if (condition) {
+    stack = null;
+  } else if (!stack) {
+    stack = new Error().stack
+      .replace(/^(.*@)http:\/\/mochi.test:8888\/tests\//gm, "    $1")
+      .split("\n");
+    stack.splice(0, 1);
+    stack = stack.join("\n");
+  }
+  SimpleTest._logResult(test, successInfo, failureInfo, stack);
+  SimpleTest._tests.push(test);
+};
+
+/**
+ * Roughly equivalent to ok(Object.is(a, b), name)
+ **/
+SimpleTest.is = function (a, b, name) {
+  // Be lazy and use Object.is til we want to test a browser without it.
+  var pass = Object.is(a, b);
+  var diag = pass ? "" : "got " + repr(a) + ", expected " + repr(b);
+  SimpleTest.record(pass, name, diag);
+};
+
+SimpleTest.isfuzzy = function (a, b, epsilon, name) {
+  var pass = a >= b - epsilon && a <= b + epsilon;
+  var diag = pass
+    ? ""
+    : "got " +
+      repr(a) +
+      ", expected " +
+      repr(b) +
+      " epsilon: +/- " +
+      repr(epsilon);
+  SimpleTest.record(pass, name, diag);
+};
+
+SimpleTest.isnot = function (a, b, name) {
+  var pass = !Object.is(a, b);
+  var diag = pass ? "" : "didn't expect " + repr(a) + ", but got it";
+  SimpleTest.record(pass, name, diag);
+};
+
+/**
+ * Check that the function call throws an exception.
+ */
+SimpleTest.doesThrow = function (fn, name) {
+  var gotException = false;
+  try {
+    fn();
+  } catch (ex) {
+    gotException = true;
+  }
+  ok(gotException, name);
+};
+
+//  --------------- Test.Builder/Test.More todo() -----------------
+
+SimpleTest.todo = function (condition, name, diag) {
+  var test = { result: !!condition, name, diag, todo: true };
+  if (
+    test.result &&
+    usesFailurePatterns() &&
+    recordIfMatchesFailurePattern(name, diag)
+  ) {
+    // Flipping the result to false so we don't get unexpected result. There
+    // is no perfect way here. A known failure can trigger unexpected pass,
+    // in which case, tagging it as KNOWN-FAIL probably makes more sense than
+    // marking it PASS.
+    test.result = false;
+    // Add a mark for unexpected failures suppressed by failure pattern.
+    name = "[suppressed] " + name;
+  }
+  var successInfo = {
+    status: "PASS",
+    expected: "FAIL",
+    message: "TEST-UNEXPECTED-PASS",
+  };
+  var failureInfo = {
+    status: "FAIL",
+    expected: "FAIL",
+    message: "TEST-KNOWN-FAIL",
+  };
+  SimpleTest._logResult(test, successInfo, failureInfo);
+  SimpleTest._tests.push(test);
+};
+
+/*
+ * Returns the absolute URL to a test data file from where tests
+ * are served. i.e. the file doesn't necessarely exists where tests
+ * are executed.
+ *
+ * (For android, mochitest are executed on the device, while
+ * all mochitest html (and others) files are served from the test runner
+ * slave)
+ */
+SimpleTest.getTestFileURL = function (path) {
+  var location = window.location;
+  // Remove mochitest html file name from the path
+  var remotePath = location.pathname.replace(/\/[^\/]+?$/, "");
+  var url = location.origin + remotePath + "/" + path;
+  return url;
+};
+
+SimpleTest._getCurrentTestURL = function () {
+  return (
+    (SimpleTest.harnessParameters &&
+      SimpleTest.harnessParameters.currentTestURL) ||
+    (parentRunner && parentRunner.currentTestURL) ||
+    (typeof gTestPath == "string" && gTestPath) ||
+    "unknown test url"
+  );
+};
+
+SimpleTest._forceLogMessageOutput = false;
+
+/**
+ * Force all test messages to be displayed.  Only applies for the current test.
+ */
+SimpleTest.requestCompleteLog = function () {
+  if (!parentRunner || SimpleTest._forceLogMessageOutput) {
+    return;
+  }
+
+  parentRunner.structuredLogger.deactivateBuffering();
+  SimpleTest._forceLogMessageOutput = true;
+
+  SimpleTest.registerCleanupFunction(function () {
+    parentRunner.structuredLogger.activateBuffering();
+    SimpleTest._forceLogMessageOutput = false;
+  });
+};
+
+SimpleTest._logResult = function (test, passInfo, failInfo, stack) {
+  var url = SimpleTest._getCurrentTestURL();
+  var result = test.result ? passInfo : failInfo;
+  var diagnostic = test.diag || null;
+  // BUGFIX : coercing test.name to a string, because some a11y tests pass an xpconnect object
+  var subtest = test.name ? String(test.name) : null;
+  var isError = !test.result == !test.todo;
+
+  if (parentRunner) {
+    if (!result.status || !result.expected) {
+      if (diagnostic) {
+        parentRunner.structuredLogger.info(diagnostic);
+      }
+      return;
+    }
+
+    if (isError) {
+      parentRunner.addFailedTest(url);
+    }
+
+    parentRunner.structuredLogger.testStatus(
+      url,
+      subtest,
+      result.status,
+      result.expected,
+      diagnostic,
+      stack
+    );
+  } else if (typeof dump === "function") {
+    var diagMessage = test.name + (test.diag ? " - " + test.diag : "");
+    var debugMsg = [result.message, url, diagMessage].join(" | ");
+    dump(debugMsg + "\n");
+  } else {
+    // Non-Mozilla browser?  Just do nothing.
+  }
+};
+
+SimpleTest.info = function (name, message) {
+  var log = message ? name + " | " + message : name;
+  if (parentRunner) {
+    parentRunner.structuredLogger.info(log);
+  } else {
+    dump(log + "\n");
+  }
+};
+
+/**
+ * Copies of is and isnot with the call to ok replaced by a call to todo.
+ **/
+
+SimpleTest.todo_is = function (a, b, name) {
+  var pass = Object.is(a, b);
+  var diag = pass
+    ? repr(a) + " should equal " + repr(b)
+    : "got " + repr(a) + ", expected " + repr(b);
+  SimpleTest.todo(pass, name, diag);
+};
+
+SimpleTest.todo_isnot = function (a, b, name) {
+  var pass = !Object.is(a, b);
+  var diag = pass
+    ? repr(a) + " should not equal " + repr(b)
+    : "didn't expect " + repr(a) + ", but got it";
+  SimpleTest.todo(pass, name, diag);
+};
+
+/**
+ * Makes a test report, returns it as a DIV element.
+ **/
+SimpleTest.report = function () {
+  var passed = 0;
+  var failed = 0;
+  var todo = 0;
+
+  var tallyAndCreateDiv = function (test) {
+    var cls, msg, div;
+    var diag = test.diag ? " - " + test.diag : "";
+    if (test.todo && !test.result) {
+      todo++;
+      cls = "test_todo";
+      msg = "todo | " + test.name + diag;
+    } else if (test.result && !test.todo) {
+      passed++;
+      cls = "test_ok";
+      msg = "passed | " + test.name + diag;
+    } else {
+      failed++;
+      cls = "test_not_ok";
+      msg = "failed | " + test.name + diag;
+    }
+    div = createEl("div", { class: cls }, msg);
+    return div;
+  };
+  var results = [];
+  for (var d = 0; d < SimpleTest._tests.length; d++) {
+    results.push(tallyAndCreateDiv(SimpleTest._tests[d]));
+  }
+
+  var summary_class =
+    // eslint-disable-next-line no-nested-ternary
+    failed != 0 ? "some_fail" : passed == 0 ? "todo_only" : "all_pass";
+
+  var div1 = createEl("div", { class: "tests_report" });
+  var div2 = createEl("div", { class: "tests_summary " + summary_class });
+  var div3 = createEl("div", { class: "tests_passed" }, "Passed: " + passed);
+  var div4 = createEl("div", { class: "tests_failed" }, "Failed: " + failed);
+  var div5 = createEl("div", { class: "tests_todo" }, "Todo: " + todo);
+  div2.appendChild(div3);
+  div2.appendChild(div4);
+  div2.appendChild(div5);
+  div1.appendChild(div2);
+  for (var t = 0; t < results.length; t++) {
+    //iterate in order
+    div1.appendChild(results[t]);
+  }
+  return div1;
+};
+
+/**
+ * Toggle element visibility
+ **/
+SimpleTest.toggle = function (el) {
+  if (computedStyle(el, "display") == "block") {
+    el.style.display = "none";
+  } else {
+    el.style.display = "block";
+  }
+};
+
+/**
+ * Toggle visibility for divs with a specific class.
+ **/
+SimpleTest.toggleByClass = function (cls, evt) {
+  var children = document.getElementsByTagName("div");
+  var elements = [];
+  for (var i = 0; i < children.length; i++) {
+    var child = children[i];
+    var clsName = child.className;
+    if (!clsName) {
+      continue;
+    }
+    var classNames = clsName.split(" ");
+    for (var j = 0; j < classNames.length; j++) {
+      if (classNames[j] == cls) {
+        elements.push(child);
+        break;
+      }
+    }
+  }
+  for (var t = 0; t < elements.length; t++) {
+    //TODO: again, for-in loop over elems seems to break this
+    SimpleTest.toggle(elements[t]);
+  }
+  if (evt) {
+    evt.preventDefault();
+  }
+};
+
+/**
+ * Shows the report in the browser
+ **/
+SimpleTest.showReport = function () {
+  var togglePassed = createEl("a", { href: "#" }, "Toggle passed checks");
+  var toggleFailed = createEl("a", { href: "#" }, "Toggle failed checks");
+  var toggleTodo = createEl("a", { href: "#" }, "Toggle todo checks");
+  togglePassed.onclick = partial(SimpleTest.toggleByClass, "test_ok");
+  toggleFailed.onclick = partial(SimpleTest.toggleByClass, "test_not_ok");
+  toggleTodo.onclick = partial(SimpleTest.toggleByClass, "test_todo");
+  var body = document.body; // Handles HTML documents
+  if (!body) {
+    // Do the XML thing.
+    body = document.getElementsByTagNameNS(
+      "http://www.w3.org/1999/xhtml",
+      "body"
+    )[0];
+  }
+  var firstChild = body.childNodes[0];
+  var addNode;
+  if (firstChild) {
+    addNode = function (el) {
+      body.insertBefore(el, firstChild);
+    };
+  } else {
+    addNode = function (el) {
+      body.appendChild(el);
+    };
+  }
+  addNode(togglePassed);
+  addNode(createEl("span", null, " "));
+  addNode(toggleFailed);
+  addNode(createEl("span", null, " "));
+  addNode(toggleTodo);
+  addNode(SimpleTest.report());
+  // Add a separator from the test content.
+  addNode(createEl("hr"));
+};
+
+/**
+ * Tells SimpleTest to don't finish the test when the document is loaded,
+ * useful for asynchronous tests.
+ *
+ * When SimpleTest.waitForExplicitFinish is called,
+ * explicit SimpleTest.finish() is required.
+ **/
+SimpleTest.waitForExplicitFinish = function () {
+  SimpleTest._stopOnLoad = false;
+};
+
+/**
+ * Multiply the timeout the parent runner uses for this test by the
+ * given factor.
+ *
+ * For example, in a test that may take a long time to complete, using
+ * "SimpleTest.requestLongerTimeout(5)" will give it 5 times as long to
+ * finish.
+ *
+ * @param {Number} factor
+ *        The multiplication factor to use on the timeout for this test.
+ */
+SimpleTest.requestLongerTimeout = function (factor) {
+  if (parentRunner) {
+    parentRunner.requestLongerTimeout(factor);
+  } else {
+    dump(
+      "[SimpleTest.requestLongerTimeout()] ignoring request, maybe you meant to call the global `requestLongerTimeout` instead?\n"
+    );
+  }
+};
+
+/**
+ * Note that the given range of assertions is to be expected.  When
+ * this function is not called, 0 assertions are expected.  When only
+ * one argument is given, that number of assertions are expected.
+ *
+ * A test where we expect to have assertions (which should largely be a
+ * transitional mechanism to get assertion counts down from our current
+ * situation) can call the SimpleTest.expectAssertions() function, with
+ * either one or two arguments:  one argument gives an exact number
+ * expected, and two arguments give a range.  For example, a test might do
+ * one of the following:
+ *
+ * @example
+ *
+ *   // Currently triggers two assertions (bug NNNNNN).
+ *   SimpleTest.expectAssertions(2);
+ *
+ *   // Currently triggers one assertion on Mac (bug NNNNNN).
+ *   if (navigator.platform.indexOf("Mac") == 0) {
+ *     SimpleTest.expectAssertions(1);
+ *   }
+ *
+ *   // Currently triggers two assertions on all platforms (bug NNNNNN),
+ *   // but intermittently triggers two additional assertions (bug NNNNNN)
+ *   // on Windows.
+ *   if (navigator.platform.indexOf("Win") == 0) {
+ *     SimpleTest.expectAssertions(2, 4);
+ *   } else {
+ *     SimpleTest.expectAssertions(2);
+ *   }
+ *
+ *   // Intermittently triggers up to three assertions (bug NNNNNN).
+ *   SimpleTest.expectAssertions(0, 3);
+ */
+SimpleTest.expectAssertions = function (min, max) {
+  if (parentRunner) {
+    parentRunner.expectAssertions(min, max);
+  }
+};
+
+SimpleTest._flakyTimeoutIsOK = false;
+SimpleTest._originalSetTimeout = window.setTimeout;
+window.setTimeout = function SimpleTest_setTimeoutShim() {
+  // Don't break tests that are loaded without a parent runner.
+  if (parentRunner) {
+    // Right now, we only enable these checks for mochitest-plain.
+    switch (SimpleTest.harnessParameters.testRoot) {
+      case "browser":
+      case "chrome":
+      case "a11y":
+        break;
+      default:
+        if (
+          !SimpleTest._alreadyFinished &&
+          arguments.length > 1 &&
+          arguments[1] > 0
+        ) {
+          if (SimpleTest._flakyTimeoutIsOK) {
+            SimpleTest.todo(
+              false,
+              "The author of the test has indicated that flaky timeouts are expected.  Reason: " +
+                SimpleTest._flakyTimeoutReason
+            );
+          } else {
+            SimpleTest.ok(
+              false,
+              "Test attempted to use a flaky timeout value " + arguments[1]
+            );
+          }
+        }
+    }
+  }
+  return SimpleTest._originalSetTimeout.apply(window, arguments);
+};
+
+/**
+ * Request the framework to allow usage of setTimeout(func, timeout)
+ * where ``timeout > 0``.  This is required to note that the author of
+ * the test is aware of the inherent flakiness in the test caused by
+ * that, and asserts that there is no way around using the magic timeout
+ * value number for some reason.
+ *
+ * Use of this function is **STRONGLY** discouraged.  Think twice before
+ * using it.  Such magic timeout values could result in intermittent
+ * failures in your test, and are almost never necessary!
+ *
+ * @param {String} reason
+ *        A string representation of the reason why the test needs timeouts.
+ *
+ */
+SimpleTest.requestFlakyTimeout = function (reason) {
+  SimpleTest.is(typeof reason, "string", "A valid string reason is expected");
+  SimpleTest.isnot(reason, "", "Reason cannot be empty");
+  SimpleTest._flakyTimeoutIsOK = true;
+  SimpleTest._flakyTimeoutReason = reason;
+};
+
+/**
+ * If the page is not yet loaded, waits for the load event. If the page is
+ * not yet focused, focuses and waits for the window to be focused.
+ * If the current page is 'about:blank', then the page is assumed to not
+ * yet be loaded. Pass true for expectBlankPage to not make this assumption
+ * if you expect a blank page to be present.
+ *
+ * The target object should be specified if it is different than 'window'. The
+ * actual focused window may be a descendant window of aObject.
+ *
+ * @param {Window|browser|BrowsingContext} [aObject]
+ *        Optional object to be focused, and may be any of:
+ *          window - a window object to focus
+ *          browser - a <browser>/<iframe> element. The top-level window
+ *                    within the frame will be focused.
+ *          browsing context - a browsing context containing a window to focus
+ *        If not specified, defaults to the global 'window'.
+ * @param {boolean} [expectBlankPage=false]
+ *        True if targetWindow.location is 'about:blank'.
+ * @param {boolean} [aBlurSubframe=false]
+ *        If true, and a subframe within the window to focus is focused, blur
+ *        it so that the specified window or browsing context will receive
+ *        focus events.
+ *
+ * @returns The browsing context that was focused.
+ */
+SimpleTest.promiseFocus = async function (
+  aObject,
+  aExpectBlankPage = false,
+  aBlurSubframe = false
+) {
+  let browser;
+  let browsingContext;
+  let windowToFocus;
+
+  if (!aObject) {
+    aObject = window;
+  }
+
+  async function waitForEvent(aTarget, aEventName) {
+    return new Promise(resolve => {
+      aTarget.addEventListener(aEventName, resolve, {
+        capture: true,
+        once: true,
+      });
+    });
+  }
+
+  if (SpecialPowers.wrap(Window).isInstance(aObject)) {
+    windowToFocus = aObject;
+
+    let isBlank = windowToFocus.location.href == "about:blank";
+    if (
+      aExpectBlankPage != isBlank ||
+      windowToFocus.document.readyState != "complete"
+    ) {
+      info("must wait for load");
+      await waitForEvent(windowToFocus, "load");
+    }
+  } else {
+    if (SpecialPowers.wrap(Element).isInstance(aObject)) {
+      // assume this is a browser/iframe element
+      browsingContext = aObject.browsingContext;
+    } else {
+      browsingContext = aObject;
+    }
+
+    browser =
+      browsingContext == aObject ? aObject.top.embedderElement : aObject;
+    windowToFocus = browser.ownerGlobal;
+  }
+
+  if (!windowToFocus.document.hasFocus()) {
+    info("must wait for focus");
+    let focusPromise = waitForEvent(windowToFocus.document, "focus");
+    SpecialPowers.focus(windowToFocus);
+    await focusPromise;
+  }
+
+  if (browser) {
+    if (windowToFocus.document.activeElement != browser) {
+      browser.focus();
+    }
+
+    info("must wait for focus in content");
+
+    // Make sure that the child process thinks it is focused as well.
+    await SpecialPowers.ensureFocus(browsingContext, aBlurSubframe);
+  } else {
+    if (aBlurSubframe) {
+      SpecialPowers.clearFocus(windowToFocus);
+    }
+
+    browsingContext = windowToFocus.browsingContext;
+  }
+
+  // Some tests rely on this delay, likely expecting layout or paint to occur.
+  await new Promise(resolve => {
+    SimpleTest.executeSoon(resolve);
+  });
+
+  return browsingContext;
+};
+
+/**
+ * Version of promiseFocus that uses a callback. For compatibility,
+ * the callback is passed one argument, the window that was focused.
+ * If the focused window is not in the same process, null is supplied.
+ */
+SimpleTest.waitForFocus = function (callback, aObject, expectBlankPage) {
+  SimpleTest.promiseFocus(aObject, expectBlankPage).then(focusedBC => {
+    callback(focusedBC?.window);
+  });
+};
+/* eslint-enable mozilla/use-services */
+
+SimpleTest.stripLinebreaksAndWhitespaceAfterTags = function (aString) {
+  return aString.replace(/(>\s*(\r\n|\n|\r)*\s*)/gm, ">");
+};
+
+/*
+ * `navigator.platform` should include this, when the platform is Windows.
+ */
+const kPlatformWindows = "Win";
+
+/*
+ * See `SimpleTest.waitForClipboard`.
+ */
+const kTextHtmlPrefixClipboardDataWindows =
+  "<html><body>\n<!--StartFragment-->";
+
+/*
+ * See `SimpleTest.waitForClipboard`.
+ */
+const kTextHtmlSuffixClipboardDataWindows =
+  "<!--EndFragment-->\n</body>\n</html>";
+
+/*
+ * Polls the clipboard waiting for the expected value. A known value different than
+ * the expected value is put on the clipboard first (and also polled for) so we
+ * can be sure the value we get isn't just the expected value because it was already
+ * on the clipboard. This only uses the global clipboard and only for text/plain
+ * values.
+ *
+ * @param {String|Function} aExpectedStringOrValidatorFn
+ *        The string value that is expected to be on the clipboard, or a
+ *        validator function getting expected clipboard data and returning a bool.
+ *        If you specify string value, line breakers in clipboard are treated
+ *        as LineFeed.  Therefore, you cannot include CarriageReturn to the
+ *        string.
+ *        If you specify string value and expect "text/html" data, this wraps
+ *        the expected value with `kTextHtmlPrefixClipboardDataWindows` and
+ *        `kTextHtmlSuffixClipboardDataWindows` only when it runs on Windows
+ *        because they are appended only by nsDataObj.cpp for Windows.
+ *        https://searchfox.org/mozilla-central/rev/8f7b017a31326515cb467e69eef1f6c965b4f00e/widget/windows/nsDataObj.cpp#1798-1805,1839-1840,1842
+ *        Therefore, you can specify selected (copied) HTML data simply on any
+ *        platforms.
+ * @param {Function} aSetupFn
+ *        A function responsible for setting the clipboard to the expected value,
+ *        called after the known value setting succeeds.
+ * @param {Function} aSuccessFn
+ *        A function called when the expected value is found on the clipboard.
+ * @param {Function} aFailureFn
+ *        A function called if the expected value isn't found on the clipboard
+ *        within 5s. It can also be called if the known value can't be found.
+ * @param {String} [aFlavor="text/plain"]
+ *        The flavor to look for.
+ * @param {Number} [aTimeout=5000]
+ *        The timeout (in milliseconds) to wait for a clipboard change.
+ * @param {boolean} [aExpectFailure=false]
+ *        If true, fail if the clipboard contents are modified within the timeout
+ *        interval defined by aTimeout.  When aExpectFailure is true, the argument
+ *        aExpectedStringOrValidatorFn must be null, as it won't be used.
+ * @param {boolean} [aDontInitializeClipboardIfExpectFailure=false]
+ *        If aExpectFailure and this is set to true, this does NOT initialize
+ *        clipboard with random data before running aSetupFn.
+ */
+SimpleTest.waitForClipboard = function (
+  aExpectedStringOrValidatorFn,
+  aSetupFn,
+  aSuccessFn,
+  aFailureFn,
+  aFlavor,
+  aTimeout,
+  aExpectFailure,
+  aDontInitializeClipboardIfExpectFailure
+) {
+  let promise = SimpleTest.promiseClipboardChange(
+    aExpectedStringOrValidatorFn,
+    aSetupFn,
+    aFlavor,
+    aTimeout,
+    aExpectFailure,
+    aDontInitializeClipboardIfExpectFailure
+  );
+  promise.then(aSuccessFn).catch(aFailureFn);
+};
+
+/**
+ * Promise-oriented version of waitForClipboard.
+ */
+SimpleTest.promiseClipboardChange = async function (
+  aExpectedStringOrValidatorFn,
+  aSetupFn,
+  aFlavor,
+  aTimeout,
+  aExpectFailure,
+  aDontInitializeClipboardIfExpectFailure
+) {
+  let requestedFlavor = aFlavor || "text/plain";
+
+  // The known value we put on the clipboard before running aSetupFn
+  let initialVal = "waitForClipboard-known-value-" + Math.random();
+  let preExpectedVal = initialVal;
+
+  let inputValidatorFn;
+  if (aExpectFailure) {
+    // If we expect failure, the aExpectedStringOrValidatorFn should be null
+    if (aExpectedStringOrValidatorFn !== null) {
+      SimpleTest.ok(
+        false,
+        "When expecting failure, aExpectedStringOrValidatorFn must be null"
+      );
+    }
+
+    inputValidatorFn = function (aData) {
+      return aData != initialVal;
+    };
+    // Build a default validator function for common string input.
+  } else if (typeof aExpectedStringOrValidatorFn == "string") {
+    if (aExpectedStringOrValidatorFn.includes("\r")) {
+      throw new Error(
+        "Use function instead of string to compare raw line breakers in clipboard"
+      );
+    }
+    if (requestedFlavor === "text/html" && navigator.platform.includes("Win")) {
+      inputValidatorFn = function (aData) {
+        return (
+          aData.replace(/\r\n?/g, "\n") ===
+          kTextHtmlPrefixClipboardDataWindows +
+            aExpectedStringOrValidatorFn +
+            kTextHtmlSuffixClipboardDataWindows
+        );
+      };
+    } else {
+      inputValidatorFn = function (aData) {
+        return aData.replace(/\r\n?/g, "\n") === aExpectedStringOrValidatorFn;
+      };
+    }
+  } else {
+    inputValidatorFn = aExpectedStringOrValidatorFn;
+  }
+
+  let maxPolls = aTimeout ? aTimeout / 100 : 50;
+
+  async function putAndVerify(operationFn, validatorFn, flavor, expectFailure) {
+    await operationFn();
+
+    let data;
+    for (let i = 0; i < maxPolls; i++) {
+      data = SpecialPowers.getClipboardData(flavor);
+      if (validatorFn(data)) {
+        // Don't show the success message when waiting for preExpectedVal
+        if (preExpectedVal) {
+          preExpectedVal = null;
+        } else {
+          SimpleTest.ok(
+            !expectFailure,
+            "Clipboard has the given value: '" + data + "'"
+          );
+        }
+
+        return data;
+      }
+
+      // Wait 100ms and check again.
+      await new Promise(resolve => {
+        SimpleTest._originalSetTimeout.apply(window, [resolve, 100]);
+      });
+    }
+
+    let errorMsg = `Timed out while polling clipboard for ${
+      preExpectedVal ? "initialized" : "requested"
+    } data, got: ${data}`;
+    SimpleTest.ok(expectFailure, errorMsg);
+    if (!expectFailure) {
+      throw new Error(errorMsg);
+    }
+    return data;
+  }
+
+  if (!aExpectFailure || !aDontInitializeClipboardIfExpectFailure) {
+    // First we wait for a known value different from the expected one.
+    SimpleTest.info(`Initializing clipboard with "${preExpectedVal}"...`);
+    await putAndVerify(
+      function () {
+        SpecialPowers.clipboardCopyString(preExpectedVal);
+      },
+      function (aData) {
+        return aData == preExpectedVal;
+      },
+      "text/plain",
+      false
+    );
+
+    SimpleTest.info(
+      "Succeeded initializing clipboard, start requested things..."
+    );
+  } else {
+    preExpectedVal = null;
+  }
+
+  return putAndVerify(
+    aSetupFn,
+    inputValidatorFn,
+    requestedFlavor,
+    aExpectFailure
+  );
+};
+
+/**
+ * Wait for a condition for a while (actually up to 3s here).
+ *
+ * @param {Function} aCond
+ *        A function returns the result of the condition
+ * @param {Function} aCallback
+ *        A function called after the condition is passed or timeout.
+ * @param {String} aErrorMsg
+ *        The message displayed when the condition failed to pass
+ *        before timeout.
+ */
+SimpleTest.waitForCondition = function (aCond, aCallback, aErrorMsg) {
+  this.promiseWaitForCondition(aCond, aErrorMsg).then(() => aCallback());
+};
+SimpleTest.promiseWaitForCondition = async function (aCond, aErrorMsg) {
+  for (let tries = 0; tries < 30; ++tries) {
+    // Wait 100ms between checks.
+    await new Promise(resolve => {
+      SimpleTest._originalSetTimeout.apply(window, [resolve, 100]);
+    });
+
+    let conditionPassed;
+    try {
+      conditionPassed = await aCond();
+    } catch (e) {
+      ok(false, `${e}\n${e.stack}`);
+      conditionPassed = false;
+    }
+    if (conditionPassed) {
+      return;
+    }
+  }
+  ok(false, aErrorMsg);
+};
+
+/**
+ * Executes a function shortly after the call, but lets the caller continue
+ * working (or finish).
+ *
+ * @param {Function} aFunc
+ *        Function to execute soon.
+ */
+SimpleTest.executeSoon = function (aFunc) {
+  if ("SpecialPowers" in window) {
+    return SpecialPowers.executeSoon(aFunc, window);
+  }
+  setTimeout(aFunc, 0);
+  return null; // Avoid warning.
+};
+
+/**
+ * Register a cleanup/teardown function (which may be async) to run after all
+ * tasks have finished, before running the next test. If async (or the function
+ * returns a promise), the framework will wait for the promise/async function
+ * to resolve.
+ *
+ * @param {Function} aFunc
+ *        The cleanup/teardown function to run.
+ */
+SimpleTest.registerCleanupFunction = function (aFunc) {
+  SimpleTest._cleanupFunctions.push(aFunc);
+};
+
+SimpleTest.registerTimeoutFunction = function (aFunc) {
+  SimpleTest._timeoutFunctions.push(aFunc);
+};
+
+SimpleTest.testInChaosMode = function () {
+  if (SimpleTest._inChaosMode) {
+    // It's already enabled for this test, don't enter twice
+    return;
+  }
+  SpecialPowers.DOMWindowUtils.enterChaosMode();
+  SimpleTest._inChaosMode = true;
+  // increase timeout here as chaosmode is very slow (i.e. 10x)
+  // doing 20x as this overwrites anything the tests set
+  SimpleTest.requestLongerTimeout(20);
+};
+
+SimpleTest.timeout = async function () {
+  for (const func of SimpleTest._timeoutFunctions) {
+    await func();
+  }
+  SimpleTest._timeoutFunctions = [];
+};
+
+SimpleTest.finishWithFailure = function (msg) {
+  SimpleTest.ok(false, msg);
+  SimpleTest.finish();
+};
+
+/**
+ * Finishes the tests. This is automatically called, except when
+ * SimpleTest.waitForExplicitFinish() has been invoked.
+ **/
+SimpleTest.finish = function () {
+  if (SimpleTest._alreadyFinished) {
+    var err =
+      "TEST-UNEXPECTED-FAIL | SimpleTest | this test already called finish!";
+    if (parentRunner) {
+      parentRunner.structuredLogger.error(err);
+    } else {
+      dump(err + "\n");
+    }
+  }
+
+  if (SimpleTest.expected == "fail" && SimpleTest.num_failed <= 0) {
+    let msg = "We expected at least one failure";
+    let test = {
+      result: false,
+      name: "fail-if condition in manifest",
+      diag: msg,
+    };
+    let successInfo = {
+      status: "FAIL",
+      expected: "FAIL",
+      message: "TEST-KNOWN-FAIL",
+    };
+    let failureInfo = {
+      status: "PASS",
+      expected: "FAIL",
+      message: "TEST-UNEXPECTED-PASS",
+    };
+    SimpleTest._logResult(test, successInfo, failureInfo);
+    SimpleTest._tests.push(test);
+  } else if (usesFailurePatterns()) {
+    SimpleTest.expected.forEach(([pat, expected_count], i) => {
+      let count = SimpleTest.num_failed[i];
+      let diag;
+      if (expected_count === null && count == 0) {
+        diag = "expected some failures but got none";
+      } else if (expected_count !== null && expected_count != count) {
+        diag = `expected ${expected_count} failures but got ${count}`;
+      } else {
+        return;
+      }
+      let name = pat
+        ? `failure pattern \`${pat}\` in this test`
+        : "failures in this test";
+      let test = { result: false, name, diag };
+      let successInfo = {
+        status: "PASS",
+        expected: "PASS",
+        message: "TEST-PASS",
+      };
+      let failureInfo = {
+        status: "FAIL",
+        expected: "PASS",
+        message: "TEST-UNEXPECTED-FAIL",
+      };
+      SimpleTest._logResult(test, successInfo, failureInfo);
+      SimpleTest._tests.push(test);
+    });
+  }
+
+  SimpleTest._timeoutFunctions = [];
+
+  SimpleTest.testsLength = SimpleTest._tests.length;
+
+  SimpleTest._alreadyFinished = true;
+
+  if (SimpleTest._inChaosMode) {
+    SpecialPowers.DOMWindowUtils.leaveChaosMode();
+    SimpleTest._inChaosMode = false;
+  }
+
+  var afterCleanup = async function () {
+    SpecialPowers.removeFiles();
+
+    if (SpecialPowers.DOMWindowUtils.isTestControllingRefreshes) {
+      SimpleTest.ok(false, "test left refresh driver under test control");
+      SpecialPowers.DOMWindowUtils.restoreNormalRefresh();
+    }
+    if (SimpleTest._expectingUncaughtException) {
+      SimpleTest.ok(
+        false,
+        "expectUncaughtException was called but no uncaught exception was detected!"
+      );
+    }
+    if (!SimpleTest._tests.length) {
+      SimpleTest.ok(
+        false,
+        "[SimpleTest.finish()] No checks actually run. " +
+          "(You need to call ok(), is(), or similar " +
+          "functions at least once.  Make sure you use " +
+          "SimpleTest.waitForExplicitFinish() if you need " +
+          "it.)"
+      );
+    }
+
+    let workers = await SpecialPowers.registeredServiceWorkers();
+    let promise = null;
+    if (SimpleTest._expectingRegisteredServiceWorker) {
+      if (workers.length === 0) {
+        SimpleTest.ok(
+          false,
+          "This test is expected to leave a service worker registered"
+        );
+      }
+    } else if (workers.length) {
+      let FULL_PROFILE_WORKERS_TO_IGNORE = [];
+      if (parentRunner.conditionedProfile) {
+        // Full profile has service workers in the profile, without clearing the profile
+        // service workers will be leftover, in all my testing youtube is the only one.
+        FULL_PROFILE_WORKERS_TO_IGNORE = ["https://www.youtube.com/sw.js"];
+      } else {
+        SimpleTest.ok(
+          false,
+          "This test left a service worker registered without cleaning it up"
+        );
+      }
+
+      for (let worker of workers) {
+        if (FULL_PROFILE_WORKERS_TO_IGNORE.includes(worker.scriptSpec)) {
+          continue;
+        }
+        SimpleTest.ok(
+          false,
+          `Left over worker: ${worker.scriptSpec} (scope: ${worker.scope})`
+        );
+      }
+      promise = SpecialPowers.removeAllServiceWorkerData();
+    }
+
+    // If we want to wait for removeAllServiceWorkerData to finish, above,
+    // there's a small chance that spinning the event loop could cause
+    // SpecialPowers and SimpleTest to go away (e.g. if the test did
+    // document.open). promise being non-null should be rare (a test would
+    // have had to already fail by leaving a service worker around), so
+    // limit the chances of the async wait happening to that case.
+    function finish() {
+      if (parentRunner) {
+        /* We're running in an iframe, and the parent has a TestRunner */
+        parentRunner.testFinished(SimpleTest._tests);
+      }
+
+      if (!parentRunner || parentRunner.showTestReport) {
+        SpecialPowers.flushPermissions(function () {
+          SpecialPowers.flushPrefEnv(function () {
+            SimpleTest.showReport();
+          });
+        });
+      }
+    }
+
+    if (promise) {
+      promise.then(finish);
+    } else {
+      finish();
+    }
+  };
+
+  var executeCleanupFunction = function () {
+    var func = SimpleTest._cleanupFunctions.pop();
+
+    if (!func) {
+      afterCleanup();
+      return;
+    }
+
+    var ret;
+    try {
+      ret = func();
+    } catch (ex) {
+      SimpleTest.ok(false, "Cleanup function threw exception: " + ex);
+    }
+
+    if (ret && ret.constructor.name == "Promise") {
+      ret.then(executeCleanupFunction, ex =>
+        SimpleTest.ok(false, "Cleanup promise rejected: " + ex)
+      );
+    } else {
+      executeCleanupFunction();
+    }
+  };
+
+  executeCleanupFunction();
+
+  SpecialPowers.notifyObservers(null, "test-complete");
+};
+
+/**
+ * Monitor console output from now until endMonitorConsole is called.
+ *
+ * Expect to receive all console messages described by the elements of
+ * ``msgs``, an array, in the order listed in ``msgs``; each element is an
+ * object which may have any number of the following properties:
+ *
+ *   message, errorMessage, sourceName, sourceLine, category: string or regexp
+ *   lineNumber, columnNumber: number
+ *   isScriptError, isWarning: boolean
+ *
+ * Strings, numbers, and booleans must compare equal to the named
+ * property of the Nth console message.  Regexps must match.  Any
+ * fields present in the message but not in the pattern object are ignored.
+ *
+ * In addition to the above properties, elements in ``msgs`` may have a ``forbid``
+ * boolean property.  When ``forbid`` is true, a failure is logged each time a
+ * matching message is received.
+ *
+ * If ``forbidUnexpectedMsgs`` is true, then the messages received in the console
+ * must exactly match the non-forbidden messages in ``msgs``; for each received
+ * message not described by the next element in ``msgs``, a failure is logged.  If
+ * false, then other non-forbidden messages are ignored, but all expected
+ * messages must still be received.
+ *
+ * After endMonitorConsole is called, ``continuation`` will be called
+ * asynchronously.  (Normally, you will want to pass ``SimpleTest.finish`` here.)
+ *
+ * It is incorrect to use this function in a test which has not called
+ * SimpleTest.waitForExplicitFinish.
+ */
+SimpleTest.monitorConsole = function (
+  continuation,
+  msgs,
+  forbidUnexpectedMsgs
+) {
+  if (SimpleTest._stopOnLoad) {
+    ok(false, "Console monitoring requires use of waitForExplicitFinish.");
+  }
+
+  function msgMatches(msg, pat) {
+    for (var k in pat) {
+      if (!(k in msg)) {
+        return false;
+      }
+      if (pat[k] instanceof RegExp && typeof msg[k] === "string") {
+        if (!pat[k].test(msg[k])) {
+          return false;
+        }
+      } else if (msg[k] !== pat[k]) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  var forbiddenMsgs = [];
+  var i = 0;
+  while (i < msgs.length) {
+    let pat = msgs[i];
+    if ("forbid" in pat) {
+      var forbid = pat.forbid;
+      delete pat.forbid;
+      if (forbid) {
+        forbiddenMsgs.push(pat);
+        msgs.splice(i, 1);
+        continue;
+      }
+    }
+    i++;
+  }
+
+  var counter = 0;
+  var assertionLabel = JSON.stringify(msgs);
+  function listener(msg) {
+    if (msg.message === "SENTINEL" && !msg.isScriptError) {
+      is(
+        counter,
+        msgs.length,
+        "monitorConsole | number of messages " + assertionLabel
+      );
+      SimpleTest.executeSoon(continuation);
+      return;
+    }
+    for (let pat of forbiddenMsgs) {
+      if (msgMatches(msg, pat)) {
+        ok(
+          false,
+          "monitorConsole | observed forbidden message " + JSON.stringify(msg)
+        );
+        return;
+      }
+    }
+    if (counter >= msgs.length) {
+      var str = "monitorConsole | extra message | " + JSON.stringify(msg);
+      if (forbidUnexpectedMsgs) {
+        ok(false, str);
+      } else {
+        info(str);
+      }
+      return;
+    }
+    var matches = msgMatches(msg, msgs[counter]);
+    if (forbidUnexpectedMsgs) {
+      ok(
+        matches,
+        "monitorConsole | [" + counter + "] must match " + JSON.stringify(msg)
+      );
+    } else {
+      info(
+        "monitorConsole | [" +
+          counter +
+          "] " +
+          (matches ? "matched " : "did not match ") +
+          JSON.stringify(msg)
+      );
+    }
+    if (matches) {
+      counter++;
+    }
+  }
+  SpecialPowers.registerConsoleListener(listener);
+};
+
+/**
+ * Stop monitoring console output.
+ */
+SimpleTest.endMonitorConsole = function () {
+  SpecialPowers.postConsoleSentinel();
+};
+
+/**
+ * Run ``testfn`` synchronously, and monitor its console output.
+ *
+ * ``msgs`` is handled as described above for monitorConsole.
+ *
+ * After ``testfn`` returns, console monitoring will stop, and ``continuation``
+ * will be called asynchronously.
+ *
+ */
+SimpleTest.expectConsoleMessages = function (testfn, msgs, continuation) {
+  SimpleTest.monitorConsole(continuation, msgs);
+  testfn();
+  SimpleTest.executeSoon(SimpleTest.endMonitorConsole);
+};
+
+/**
+ * Wrapper around ``expectConsoleMessages`` for the case where the test has
+ * only one ``testfn`` to run.
+ */
+SimpleTest.runTestExpectingConsoleMessages = function (testfn, msgs) {
+  SimpleTest.waitForExplicitFinish();
+  SimpleTest.expectConsoleMessages(testfn, msgs, SimpleTest.finish);
+};
+
+/**
+ * Indicates to the test framework that the current test expects one or
+ * more crashes (from plugins or IPC documents), and that the minidumps from
+ * those crashes should be removed.
+ */
+SimpleTest.expectChildProcessCrash = function () {
+  if (parentRunner) {
+    parentRunner.expectChildProcessCrash();
+  }
+};
+
+/**
+ * Indicates to the test framework that the next uncaught exception during
+ * the test is expected, and should not cause a test failure.
+ */
+SimpleTest.expectUncaughtException = function (aExpecting) {
+  SimpleTest._expectingUncaughtException =
+    aExpecting === void 0 || !!aExpecting;
+};
+
+/**
+ * Returns whether the test has indicated that it expects an uncaught exception
+ * to occur.
+ */
+SimpleTest.isExpectingUncaughtException = function () {
+  return SimpleTest._expectingUncaughtException;
+};
+
+/**
+ * Indicates to the test framework that all of the uncaught exceptions
+ * during the test are known problems that should be fixed in the future,
+ * but which should not cause the test to fail currently.
+ */
+SimpleTest.ignoreAllUncaughtExceptions = function (aIgnoring) {
+  SimpleTest._ignoringAllUncaughtExceptions =
+    aIgnoring === void 0 || !!aIgnoring;
+};
+
+/**
+ * Returns whether the test has indicated that all uncaught exceptions should be
+ * ignored.
+ */
+SimpleTest.isIgnoringAllUncaughtExceptions = function () {
+  return SimpleTest._ignoringAllUncaughtExceptions;
+};
+
+/**
+ * Indicates to the test framework that this test is expected to leave a
+ * service worker registered when it finishes.
+ */
+SimpleTest.expectRegisteredServiceWorker = function () {
+  SimpleTest._expectingRegisteredServiceWorker = true;
+};
+
+/**
+ * Resets any state this SimpleTest object has.  This is important for
+ * browser chrome mochitests, which reuse the same SimpleTest object
+ * across a run.
+ */
+SimpleTest.reset = function () {
+  SimpleTest._ignoringAllUncaughtExceptions = false;
+  SimpleTest._expectingUncaughtException = false;
+  SimpleTest._expectingRegisteredServiceWorker = false;
+  SimpleTest._bufferedMessages = [];
+};
+
+if (isPrimaryTestWindow) {
+  addLoadEvent(function () {
+    if (SimpleTest._stopOnLoad) {
+      SimpleTest.finish();
+    }
+  });
+}
+
+//  --------------- Test.Builder/Test.More isDeeply() -----------------
+
+SimpleTest.DNE = { dne: "Does not exist" };
+SimpleTest.LF = "\r\n";
+
+SimpleTest._deepCheck = function (e1, e2, stack, seen) {
+  var ok = false;
+  if (Object.is(e1, e2)) {
+    // Handles identical primitives and references.
+    ok = true;
+  } else if (
+    typeof e1 != "object" ||
+    typeof e2 != "object" ||
+    e1 === null ||
+    e2 === null
+  ) {
+    // If either argument is a primitive or function, don't consider the arguments the same.
+    ok = false;
+  } else if (e1 == SimpleTest.DNE || e2 == SimpleTest.DNE) {
+    ok = false;
+  } else if (SimpleTest.isa(e1, "Array") && SimpleTest.isa(e2, "Array")) {
+    ok = SimpleTest._eqArray(e1, e2, stack, seen);
+  } else {
+    ok = SimpleTest._eqAssoc(e1, e2, stack, seen);
+  }
+  return ok;
+};
+
+SimpleTest._eqArray = function (a1, a2, stack, seen) {
+  // Return if they're the same object.
+  if (a1 == a2) {
+    return true;
+  }
+
+  // JavaScript objects have no unique identifiers, so we have to store
+  // references to them all in an array, and then compare the references
+  // directly. It's slow, but probably won't be much of an issue in
+  // practice. Start by making a local copy of the array to as to avoid
+  // confusing a reference seen more than once (such as [a, a]) for a
+  // circular reference.
+  for (var j = 0; j < seen.length; j++) {
+    if (seen[j][0] == a1) {
+      return seen[j][1] == a2;
+    }
+  }
+
+  // If we get here, we haven't seen a1 before, so store it with reference
+  // to a2.
+  seen.push([a1, a2]);
+
+  var ok = true;
+  // Only examines enumerable attributes. Only works for numeric arrays!
+  // Associative arrays return 0. So call _eqAssoc() for them, instead.
+  var max = Math.max(a1.length, a2.length);
+  if (max == 0) {
+    return SimpleTest._eqAssoc(a1, a2, stack, seen);
+  }
+  for (var i = 0; i < max; i++) {
+    var e1 = i < a1.length ? a1[i] : SimpleTest.DNE;
+    var e2 = i < a2.length ? a2[i] : SimpleTest.DNE;
+    stack.push({ type: "Array", idx: i, vals: [e1, e2] });
+    ok = SimpleTest._deepCheck(e1, e2, stack, seen);
+    if (ok) {
+      stack.pop();
+    } else {
+      break;
+    }
+  }
+  return ok;
+};
+
+SimpleTest._eqAssoc = function (o1, o2, stack, seen) {
+  // Return if they're the same object.
+  if (o1 == o2) {
+    return true;
+  }
+
+  // JavaScript objects have no unique identifiers, so we have to store
+  // references to them all in an array, and then compare the references
+  // directly. It's slow, but probably won't be much of an issue in
+  // practice. Start by making a local copy of the array to as to avoid
+  // confusing a reference seen more than once (such as [a, a]) for a
+  // circular reference.
+  seen = seen.slice(0);
+  for (let j = 0; j < seen.length; j++) {
+    if (seen[j][0] == o1) {
+      return seen[j][1] == o2;
+    }
+  }
+
+  // If we get here, we haven't seen o1 before, so store it with reference
+  // to o2.
+  seen.push([o1, o2]);
+
+  // They should be of the same class.
+
+  var ok = true;
+  // Only examines enumerable attributes.
+  var o1Size = 0;
+  // eslint-disable-next-line no-unused-vars
+  for (let i in o1) {
+    o1Size++;
+  }
+  var o2Size = 0;
+  // eslint-disable-next-line no-unused-vars
+  for (let i in o2) {
+    o2Size++;
+  }
+  var bigger = o1Size > o2Size ? o1 : o2;
+  for (let i in bigger) {
+    var e1 = i in o1 ? o1[i] : SimpleTest.DNE;
+    var e2 = i in o2 ? o2[i] : SimpleTest.DNE;
+    stack.push({ type: "Object", idx: i, vals: [e1, e2] });
+    ok = SimpleTest._deepCheck(e1, e2, stack, seen);
+    if (ok) {
+      stack.pop();
+    } else {
+      break;
+    }
+  }
+  return ok;
+};
+
+SimpleTest._formatStack = function (stack) {
+  var variable = "$Foo";
+  for (let i = 0; i < stack.length; i++) {
+    var entry = stack[i];
+    var type = entry.type;
+    var idx = entry.idx;
+    if (idx != null) {
+      if (type == "Array") {
+        // Numeric array index.
+        variable += "[" + idx + "]";
+      } else {
+        // Associative array index.
+        idx = idx.replace("'", "\\'");
+        variable += "['" + idx + "']";
+      }
+    }
+  }
+
+  var vals = stack[stack.length - 1].vals.slice(0, 2);
+  var vars = [
+    variable.replace("$Foo", "got"),
+    variable.replace("$Foo", "expected"),
+  ];
+
+  var out = "Structures begin differing at:" + SimpleTest.LF;
+  for (let i = 0; i < vals.length; i++) {
+    var val = vals[i];
+    if (val === SimpleTest.DNE) {
+      val = "Does not exist";
+    } else {
+      val = repr(val);
+    }
+    out += vars[i] + " = " + val + SimpleTest.LF;
+  }
+
+  return "    " + out;
+};
+
+SimpleTest.isDeeply = function (it, as, name) {
+  var stack = [{ vals: [it, as] }];
+  var seen = [];
+  if (SimpleTest._deepCheck(it, as, stack, seen)) {
+    SimpleTest.record(true, name);
+  } else {
+    SimpleTest.record(false, name, SimpleTest._formatStack(stack));
+  }
+};
+
+SimpleTest.typeOf = function (object) {
+  var c = Object.prototype.toString.apply(object);
+  var name = c.substring(8, c.length - 1);
+  if (name != "Object") {
+    return name;
+  }
+  // It may be a non-core class. Try to extract the class name from
+  // the constructor function. This may not work in all implementations.
+  if (/function ([^(\s]+)/.test(Function.toString.call(object.constructor))) {
+    return RegExp.$1;
+  }
+  // No idea. :-(
+  return name;
+};
+
+SimpleTest.isa = function (object, clas) {
+  return SimpleTest.typeOf(object) == clas;
+};
+
+// Global symbols:
+var ok = SimpleTest.ok;
+var record = SimpleTest.record;
+var is = SimpleTest.is;
+var isfuzzy = SimpleTest.isfuzzy;
+var isnot = SimpleTest.isnot;
+var todo = SimpleTest.todo;
+var todo_is = SimpleTest.todo_is;
+var todo_isnot = SimpleTest.todo_isnot;
+var isDeeply = SimpleTest.isDeeply;
+var info = SimpleTest.info;
+
+var gOldOnError = window.onerror;
+window.onerror = function simpletestOnerror(
+  errorMsg,
+  url,
+  lineNumber,
+  columnNumber,
+  originalException
+) {
+  // Log the message.
+  // XXX Chrome mochitests sometimes trigger this window.onerror handler,
+  // but there are a number of uncaught JS exceptions from those tests.
+  // For now, for tests that self identify as having unintentional uncaught
+  // exceptions, just dump it so that the error is visible but doesn't cause
+  // a test failure.  See bug 652494.
+  var isExpected = !!SimpleTest._expectingUncaughtException;
+  var message = (isExpected ? "expected " : "") + "uncaught exception";
+  var error = errorMsg + " at ";
+  try {
+    error += originalException.stack;
+  } catch (e) {
+    // At least use the url+line+column we were given
+    error += url + ":" + lineNumber + ":" + columnNumber;
+  }
+  if (!SimpleTest._ignoringAllUncaughtExceptions) {
+    // Don't log if SimpleTest.finish() is already called, it would cause failures
+    if (!SimpleTest._alreadyFinished) {
+      SimpleTest.record(isExpected, message, error);
+    }
+    SimpleTest._expectingUncaughtException = false;
+  } else {
+    SimpleTest.todo(false, message + ": " + error);
+  }
+  // There is no Components.stack.caller to log. (See bug 511888.)
+
+  // Call previous handler.
+  if (gOldOnError) {
+    try {
+      // Ignore return value: always run default handler.
+      gOldOnError(errorMsg, url, lineNumber);
+    } catch (e) {
+      // Log the error.
+      SimpleTest.info("Exception thrown by gOldOnError(): " + e);
+      // Log its stack.
+      if (e.stack) {
+        SimpleTest.info("JavaScript error stack:\n" + e.stack);
+      }
+    }
+  }
+
+  if (!SimpleTest._stopOnLoad && !isExpected && !SimpleTest._alreadyFinished) {
+    // Need to finish() manually here, yet let the test actually end first.
+    SimpleTest.executeSoon(SimpleTest.finish);
+  }
+};
+
+// Lifted from dom/media/test/manifest.js
+// Make sure to not touch navigator in here, since we want to push prefs that
+// will affect the APIs it exposes, but the set of exposed APIs is determined
+// when Navigator.prototype is created.  So if we touch navigator before pushing
+// the prefs, the APIs it exposes will not take those prefs into account.  We
+// work around this by using a navigator object from a different global for our
+// UA string testing.
+var gAndroidSdk = null;
+function getAndroidSdk() {
+  if (gAndroidSdk === null) {
+    var iframe = document.documentElement.appendChild(
+      document.createElement("iframe")
+    );
+    iframe.style.display = "none";
+    var nav = iframe.contentWindow.navigator;
+    if (
+      !nav.userAgent.includes("Mobile") &&
+      !nav.userAgent.includes("Tablet")
+    ) {
+      gAndroidSdk = -1;
+    } else {
+      // See nsSystemInfo.cpp, the getProperty('version') returns different value
+      // on each platforms, so we need to distinguish the android platform.
+      var versionString = nav.userAgent.includes("Android")
+        ? "version"
+        : "sdk_version";
+      gAndroidSdk = SpecialPowers.Services.sysinfo.getProperty(versionString);
+    }
+    document.documentElement.removeChild(iframe);
+  }
+  return gAndroidSdk;
+}
+
+// add_task(generatorFunction):
+// Call `add_task(generatorFunction)` for each separate
+// asynchronous task in a mochitest. Tasks are run consecutively.
+// Before the first task, `SimpleTest.waitForExplicitFinish()`
+// will be called automatically, and after the last task,
+// `SimpleTest.finish()` will be called.
+var add_task = (function () {
+  // The list of tasks to run.
+  var task_list = [];
+  var run_only_this_task = null;
+
+  function isGenerator(value) {
+    return (
+      value && typeof value === "object" && typeof value.next === "function"
+    );
+  }
+
+  // The "add_task" function
+  return function (generatorFunction, options = { isSetup: false }) {
+    if (task_list.length === 0) {
+      // This is the first time add_task has been called.
+      // First, confirm that SimpleTest is available.
+      if (!SimpleTest) {
+        throw new Error("SimpleTest not available.");
+      }
+      // Don't stop tests until asynchronous tasks are finished.
+      SimpleTest.waitForExplicitFinish();
+      // Because the client is using add_task for this set of tests,
+      // we need to spawn a "master task" that calls each task in succesion.
+      // Use setTimeout to ensure the master task runs after the client
+      // script finishes.
+      setTimeout(function nextTick() {
+        // If we are in a HTML document, we should wait for the document
+        // to be fully loaded.
+        // These checks ensure that we are in an HTML document without
+        // throwing TypeError; also I am told that readyState in XUL documents
+        // are totally bogus so we don't try to do this there.
+        if (
+          typeof window !== "undefined" &&
+          typeof HTMLDocument !== "undefined" &&
+          window.document instanceof HTMLDocument &&
+          window.document.readyState !== "complete"
+        ) {
+          setTimeout(nextTick);
+          return;
+        }
+
+        (async () => {
+          // Allow for a task to be skipped; we need only use the structured logger
+          // for this, whilst deactivating log buffering to ensure that messages
+          // are always printed to stdout.
+          function skipTask(name) {
+            let logger = parentRunner && parentRunner.structuredLogger;
+            if (!logger) {
+              info("add_task | Skipping test " + name);
+              return;
+            }
+            logger.deactivateBuffering();
+            logger.testStatus(SimpleTest._getCurrentTestURL(), name, "SKIP");
+            logger.warning("add_task | Skipping test " + name);
+            logger.activateBuffering();
+          }
+
+          // We stop the entire test file at the first exception because this
+          // may mean that the state of subsequent tests may be corrupt.
+          try {
+            for (var task of task_list) {
+              var name = task.name || "";
+              if (
+                task.__skipMe ||
+                (run_only_this_task && task != run_only_this_task)
+              ) {
+                skipTask(name);
+                continue;
+              }
+              const taskInfo = action =>
+                info(
+                  `${
+                    task.isSetup ? "add_setup" : "add_task"
+                  } | ${action} ${name}`
+                );
+              taskInfo("Entering");
+              let result = await task();
+              if (isGenerator(result)) {
+                ok(false, "Task returned a generator");
+              }
+              taskInfo("Leaving");
+            }
+          } catch (ex) {
+            try {
+              let serializedEx;
+              if (
+                typeof ex == "string" ||
+                (typeof ex == "object" && isErrorOrException(ex))
+              ) {
+                serializedEx = `${ex}`;
+              } else {
+                serializedEx = JSON.stringify(ex);
+              }
+
+              SimpleTest.record(
+                false,
+                serializedEx,
+                "Should not throw any errors",
+                ex.stack
+              );
+            } catch (ex2) {
+              SimpleTest.record(
+                false,
+                "(The exception cannot be converted to string.)",
+                "Should not throw any errors",
+                ex.stack
+              );
+            }
+          }
+          // All tasks are finished.
+          SimpleTest.finish();
+        })();
+      });
+    }
+    generatorFunction.skip = () => (generatorFunction.__skipMe = true);
+    generatorFunction.only = () => (run_only_this_task = generatorFunction);
+    // Add the task to the list of tasks to run after
+    // the main thread is finished.
+    if (options.isSetup) {
+      generatorFunction.isSetup = true;
+      let lastSetupIndex = task_list.findLastIndex(t => t.isSetup) + 1;
+      task_list.splice(lastSetupIndex, 0, generatorFunction);
+    } else {
+      task_list.push(generatorFunction);
+    }
+    return generatorFunction;
+  };
+})();
+
+// Like add_task, but setup tasks are executed first.
+function add_setup(generatorFunction) {
+  return add_task(generatorFunction, { isSetup: true });
+}
+
+// Request complete log when using failure patterns so that failure info
+// from infra can be useful.
+if (usesFailurePatterns()) {
+  SimpleTest.requestCompleteLog();
+}
+
+addEventListener("message", async event => {
+  if (event.data == "SimpleTest:timeout") {
+    await SimpleTest.timeout();
+    SimpleTest.finish();
+  }
+});
diff --git a/testing/mochitest/tests/SimpleTest/TestRunner.js b/testing/mochitest/tests/SimpleTest/TestRunner.js
new file mode 100644
index 0000000000..6efcec9f85
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/TestRunner.js
@@ -0,0 +1,1103 @@
+/* -*- js-indent-level: 4; indent-tabs-mode: nil -*- */
+/*
+ * e10s event dispatcher from content->chrome
+ *
+ * type = eventName (QuitApplication)
+ * data = json object {"filename":filename} <- for LoggerInit
+ */
+
+// This file expects the following files to be loaded.
+/* import-globals-from LogController.js */
+/* import-globals-from MemoryStats.js */
+/* import-globals-from MozillaLogger.js */
+
+/* eslint-disable no-unsanitized/property */
+
+"use strict";
+
+const { StructuredLogger, StructuredFormatter } =
+  SpecialPowers.ChromeUtils.importESModule(
+    "resource://testing-common/StructuredLog.sys.mjs"
+  );
+
+function getElement(id) {
+  return typeof id == "string" ? document.getElementById(id) : id;
+}
+
+this.$ = this.getElement;
+
+function contentDispatchEvent(type, data, sync) {
+  if (typeof data == "undefined") {
+    data = {};
+  }
+
+  var event = new CustomEvent("contentEvent", {
+    bubbles: true,
+    detail: {
+      sync,
+      type,
+      data: JSON.stringify(data),
+    },
+  });
+  document.dispatchEvent(event);
+}
+
+function contentAsyncEvent(type, data) {
+  contentDispatchEvent(type, data, 0);
+}
+
+/* Helper Function */
+function extend(obj, /* optional */ skip) {
+  // Extend an array with an array-like object starting
+  // from the skip index
+  if (!skip) {
+    skip = 0;
+  }
+  if (obj) {
+    var l = obj.length;
+    var ret = [];
+    for (var i = skip; i < l; i++) {
+      ret.push(obj[i]);
+    }
+  }
+  return ret;
+}
+
+function flattenArguments(lst /* ...*/) {
+  var res = [];
+  var args = extend(arguments);
+  while (args.length) {
+    var o = args.shift();
+    if (o && typeof o == "object" && typeof o.length == "number") {
+      for (var i = o.length - 1; i >= 0; i--) {
+        args.unshift(o[i]);
+      }
+    } else {
+      res.push(o);
+    }
+  }
+  return res;
+}
+
+function testInXOriginFrame() {
+  // Check if the test running in an iframe is a cross origin test.
+  try {
+    $("testframe").contentWindow.origin;
+    return false;
+  } catch (e) {
+    return true;
+  }
+}
+
+function testInDifferentProcess() {
+  // Check if the test running in an iframe that is loaded in a different process.
+  return SpecialPowers.Cu.isRemoteProxy($("testframe").contentWindow);
+}
+
+/**
+ * TestRunner: A test runner for SimpleTest
+ * TODO:
+ *
+ *  * Avoid moving iframes: That causes reloads on mozilla and opera.
+ *
+ *
+ **/
+var TestRunner = {};
+TestRunner.logEnabled = false;
+TestRunner._currentTest = 0;
+TestRunner._lastTestFinished = -1;
+TestRunner._loopIsRestarting = false;
+TestRunner.currentTestURL = "";
+TestRunner.originalTestURL = "";
+TestRunner._urls = [];
+TestRunner._lastAssertionCount = 0;
+TestRunner._expectedMinAsserts = 0;
+TestRunner._expectedMaxAsserts = 0;
+
+TestRunner.timeout = 300 * 1000; // 5 minutes.
+TestRunner.maxTimeouts = 4; // halt testing after too many timeouts
+TestRunner.runSlower = false;
+TestRunner.dumpOutputDirectory = "";
+TestRunner.dumpAboutMemoryAfterTest = false;
+TestRunner.dumpDMDAfterTest = false;
+TestRunner.slowestTestTime = 0;
+TestRunner.slowestTestURL = "";
+TestRunner.interactiveDebugger = false;
+TestRunner.cleanupCrashes = false;
+TestRunner.timeoutAsPass = false;
+TestRunner.conditionedProfile = false;
+TestRunner.comparePrefs = false;
+
+TestRunner._expectingProcessCrash = false;
+TestRunner._structuredFormatter = new StructuredFormatter();
+
+/**
+ * Make sure the tests don't hang indefinitely.
+ **/
+TestRunner._numTimeouts = 0;
+TestRunner._currentTestStartTime = new Date().valueOf();
+TestRunner._timeoutFactor = 1;
+
+/**
+ * Used to collect code coverage with the js debugger.
+ */
+TestRunner.jscovDirPrefix = "";
+var coverageCollector = {};
+
+function record(succeeded, expectedFail, msg) {
+  let successInfo;
+  let failureInfo;
+  if (expectedFail) {
+    successInfo = {
+      status: "PASS",
+      expected: "FAIL",
+      message: "TEST-UNEXPECTED-PASS",
+    };
+    failureInfo = {
+      status: "FAIL",
+      expected: "FAIL",
+      message: "TEST-KNOWN-FAIL",
+    };
+  } else {
+    successInfo = {
+      status: "PASS",
+      expected: "PASS",
+      message: "TEST-PASS",
+    };
+    failureInfo = {
+      status: "FAIL",
+      expected: "PASS",
+      message: "TEST-UNEXPECTED-FAIL",
+    };
+  }
+
+  let result = succeeded ? successInfo : failureInfo;
+
+  TestRunner.structuredLogger.testStatus(
+    TestRunner.currentTestURL,
+    msg,
+    result.status,
+    result.expected,
+    "",
+    ""
+  );
+}
+
+TestRunner._checkForHangs = function () {
+  function reportError(win, msg) {
+    if (testInXOriginFrame() || "SimpleTest" in win) {
+      record(false, TestRunner.timeoutAsPass, msg);
+    } else if ("W3CTest" in win) {
+      win.W3CTest.logFailure(msg);
+    }
+  }
+
+  async function killTest(win) {
+    if (testInXOriginFrame()) {
+      win.postMessage("SimpleTest:timeout", "*");
+    } else if ("SimpleTest" in win) {
+      await win.SimpleTest.timeout();
+      win.SimpleTest.finish();
+    } else if ("W3CTest" in win) {
+      await win.W3CTest.timeout();
+    }
+  }
+
+  if (TestRunner._currentTest < TestRunner._urls.length) {
+    var runtime = new Date().valueOf() - TestRunner._currentTestStartTime;
+    if (runtime >= TestRunner.timeout * TestRunner._timeoutFactor) {
+      let testIframe = $("testframe");
+      var frameWindow =
+        (!testInXOriginFrame() && testIframe.contentWindow.wrappedJSObject) ||
+        testIframe.contentWindow;
+      reportError(frameWindow, "Test timed out.");
+      TestRunner.updateUI([{ result: false }]);
+
+      // If we have too many timeouts, give up. We don't want to wait hours
+      // for results if some bug causes lots of tests to time out.
+      if (++TestRunner._numTimeouts >= TestRunner.maxTimeouts) {
+        TestRunner._haltTests = true;
+
+        TestRunner.currentTestURL = "(SimpleTest/TestRunner.js)";
+        reportError(
+          frameWindow,
+          TestRunner.maxTimeouts + " test timeouts, giving up."
+        );
+        var skippedTests = TestRunner._urls.length - TestRunner._currentTest;
+        reportError(
+          frameWindow,
+          "Skipping " + skippedTests + " remaining tests."
+        );
+      }
+
+      // Add a little (1 second) delay to ensure automation.py has time to notice
+      // "Test timed out" log and process it (= take a screenshot).
+      setTimeout(async function delayedKillTest() {
+        try {
+          await killTest(frameWindow);
+        } catch (e) {
+          reportError(frameWindow, "Test error: " + e);
+          TestRunner.updateUI([{ result: false }]);
+        }
+      }, 1000);
+
+      if (TestRunner._haltTests) {
+        return;
+      }
+    }
+
+    setTimeout(TestRunner._checkForHangs, 30000);
+  }
+};
+
+TestRunner.requestLongerTimeout = function (factor) {
+  TestRunner._timeoutFactor = factor;
+};
+
+/**
+ * This is used to loop tests
+ **/
+TestRunner.repeat = 0;
+TestRunner._currentLoop = 1;
+
+TestRunner.expectAssertions = function (min, max) {
+  if (typeof max == "undefined") {
+    max = min;
+  }
+  if (
+    typeof min != "number" ||
+    typeof max != "number" ||
+    min < 0 ||
+    max < min
+  ) {
+    throw new Error("bad parameter to expectAssertions");
+  }
+  TestRunner._expectedMinAsserts = min;
+  TestRunner._expectedMaxAsserts = max;
+};
+
+/**
+ * This function is called after generating the summary.
+ **/
+TestRunner.onComplete = null;
+
+/**
+ * Adds a failed test case to a list so we can rerun only the failed tests
+ **/
+TestRunner._failedTests = {};
+TestRunner._failureFile = "";
+
+TestRunner.addFailedTest = function (testName) {
+  if (TestRunner._failedTests[testName] == undefined) {
+    TestRunner._failedTests[testName] = "";
+  }
+};
+
+TestRunner.setFailureFile = function (fileName) {
+  TestRunner._failureFile = fileName;
+};
+
+TestRunner.generateFailureList = function () {
+  if (TestRunner._failureFile) {
+    var failures = new MozillaFileLogger(TestRunner._failureFile);
+    failures.log(JSON.stringify(TestRunner._failedTests));
+    failures.close();
+  }
+};
+
+/**
+ * If logEnabled is true, this is the logger that will be used.
+ **/
+
+// This delimiter is used to avoid interleaving Mochitest/Gecko logs.
+var LOG_DELIMITER = "\ue175\uee31\u2c32\uacbf";
+
+// A log callback for StructuredLog.sys.mjs
+TestRunner._dumpMessage = function (message) {
+  var str;
+
+  // This is a directive to python to format these messages
+  // for compatibility with mozharness. This can be removed
+  // with the MochitestFormatter (see bug 1045525).
+  message.js_source = "TestRunner.js";
+  if (
+    TestRunner.interactiveDebugger &&
+    message.action in TestRunner._structuredFormatter
+  ) {
+    str = TestRunner._structuredFormatter[message.action](message);
+  } else {
+    str = LOG_DELIMITER + JSON.stringify(message) + LOG_DELIMITER;
+  }
+  // BUGFIX: browser-chrome tests don't use LogController
+  if (Object.keys(LogController.listeners).length !== 0) {
+    LogController.log(str);
+  } else {
+    dump("\n" + str + "\n");
+  }
+  // Checking for error messages
+  if (message.expected || message.level === "ERROR") {
+    TestRunner.failureHandler();
+  }
+};
+
+// From https://searchfox.org/mozilla-central/source/testing/modules/StructuredLog.sys.mjs
+TestRunner.structuredLogger = new StructuredLogger(
+  "mochitest",
+  TestRunner._dumpMessage,
+  [],
+  TestRunner
+);
+TestRunner.structuredLogger.deactivateBuffering = function () {
+  TestRunner.structuredLogger.logData("buffering_off");
+};
+TestRunner.structuredLogger.activateBuffering = function () {
+  TestRunner.structuredLogger.logData("buffering_on");
+};
+
+TestRunner.log = function (msg) {
+  if (TestRunner.logEnabled) {
+    TestRunner.structuredLogger.info(msg);
+  } else {
+    dump(msg + "\n");
+  }
+};
+
+TestRunner.error = function (msg) {
+  if (TestRunner.logEnabled) {
+    TestRunner.structuredLogger.error(msg);
+  } else {
+    dump(msg + "\n");
+    TestRunner.failureHandler();
+  }
+};
+
+TestRunner.failureHandler = function () {
+  if (TestRunner.runUntilFailure) {
+    TestRunner._haltTests = true;
+  }
+
+  if (TestRunner.debugOnFailure) {
+    // You've hit this line because you requested to break into the
+    // debugger upon a testcase failure on your test run.
+    // eslint-disable-next-line no-debugger
+    debugger;
+  }
+};
+
+/**
+ * Toggle element visibility
+ **/
+TestRunner._toggle = function (el) {
+  if (el.className == "noshow") {
+    el.className = "";
+    el.style.cssText = "";
+  } else {
+    el.className = "noshow";
+    el.style.cssText = "width:0px; height:0px; border:0px;";
+  }
+};
+
+/**
+ * Creates the iframe that contains a test
+ **/
+TestRunner._makeIframe = function (url, retry) {
+  var iframe = $("testframe");
+  if (
+    url != "about:blank" &&
+    (("hasFocus" in document && !document.hasFocus()) ||
+      ("activeElement" in document && document.activeElement != iframe))
+  ) {
+    contentAsyncEvent("Focus");
+    window.focus();
+    SpecialPowers.focus();
+    iframe.focus();
+    if (retry < 3) {
+      window.setTimeout(function () {
+        TestRunner._makeIframe(url, retry + 1);
+      }, 1000);
+      return;
+    }
+
+    TestRunner.structuredLogger.info(
+      "Error: Unable to restore focus, expect failures and timeouts."
+    );
+  }
+  window.scrollTo(0, $("indicator").offsetTop);
+  try {
+    let urlObj = new URL(url);
+    if (TestRunner.xOriginTests) {
+      // The test will run in a xorigin iframe, so we pass in additional test params in the
+      // URL since the content process won't be able to access them from the parentRunner
+      // directly.
+      let params = TestRunner.getParameterInfo();
+      urlObj.searchParams.append(
+        "currentTestURL",
+        urlObj.pathname.replace("/tests/", "")
+      );
+      urlObj.searchParams.append("closeWhenDone", params.closeWhenDone);
+      urlObj.searchParams.append("showTestReport", TestRunner.showTestReport);
+      urlObj.searchParams.append("expected", TestRunner.expected);
+      iframe.src = urlObj.href;
+    } else {
+      iframe.src = url;
+    }
+  } catch {
+    // If the provided `url` is not a valid URL (i.e. doesn't include a protocol)
+    // then the new URL() constructor will raise a TypeError. This is expected in the
+    // usual case (i.e. non-xorigin iFrame tests) so set the URL in the usual way.
+    iframe.src = url;
+  }
+  iframe.name = url;
+  iframe.width = "500";
+};
+
+/**
+ * Returns the current test URL.
+ * We use this to tell whether the test has navigated to another test without
+ * being finished first.
+ */
+TestRunner.getLoadedTestURL = function () {
+  if (!testInXOriginFrame()) {
+    var prefix = "";
+    // handle mochitest-chrome URIs
+    if ($("testframe").contentWindow.location.protocol == "chrome:") {
+      prefix = "chrome://mochitests";
+    }
+    return prefix + $("testframe").contentWindow.location.pathname;
+  }
+  return TestRunner.currentTestURL;
+};
+
+TestRunner.setParameterInfo = function (params) {
+  this._params = params;
+};
+
+TestRunner.getParameterInfo = function () {
+  return this._params;
+};
+
+/**
+ * Print information about which prefs are set.
+ * This is used to help validate that the tests are actually
+ * running in the expected context.
+ */
+TestRunner.dumpPrefContext = function () {
+  let prefs = ["fission.autostart"];
+
+  let message = ["Dumping test context:"];
+  prefs.forEach(function formatPref(pref) {
+    let val = SpecialPowers.getBoolPref(pref);
+    message.push(pref + "=" + val);
+  });
+  TestRunner.structuredLogger.info(message.join("\n  "));
+};
+
+/**
+ * TestRunner entry point.
+ *
+ * The arguments are the URLs of the test to be ran.
+ *
+ **/
+TestRunner.runTests = function (/*url...*/) {
+  TestRunner.structuredLogger.info("SimpleTest START");
+  TestRunner.dumpPrefContext();
+  TestRunner.originalTestURL = $("current-test").innerHTML;
+
+  SpecialPowers.registerProcessCrashObservers();
+
+  // Initialize code coverage
+  if (TestRunner.jscovDirPrefix != "") {
+    var { CoverageCollector } = SpecialPowers.ChromeUtils.importESModule(
+      "resource://testing-common/CoverageUtils.sys.mjs"
+    );
+    coverageCollector = new CoverageCollector(TestRunner.jscovDirPrefix);
+  }
+
+  SpecialPowers.requestResetCoverageCounters().then(() => {
+    TestRunner._urls = flattenArguments(arguments);
+
+    var singleTestRun = this._urls.length <= 1 && TestRunner.repeat <= 1;
+    TestRunner.showTestReport = singleTestRun;
+    var frame = $("testframe");
+    frame.src = "";
+    if (singleTestRun) {
+      // Can't use document.body because this runs in a XUL doc as well...
+      var body = document.getElementsByTagName("body")[0];
+      body.setAttribute("singletest", "true");
+      frame.removeAttribute("scrolling");
+    }
+    TestRunner._checkForHangs();
+    TestRunner.runNextTest();
+  });
+};
+
+/**
+ * Used for running a set of tests in a loop for debugging purposes
+ * Takes an array of URLs
+ **/
+TestRunner.resetTests = function (listURLs) {
+  TestRunner._currentTest = 0;
+  // Reset our "Current-test" line - functionality depends on it
+  $("current-test").innerHTML = TestRunner.originalTestURL;
+  if (TestRunner.logEnabled) {
+    TestRunner.structuredLogger.info(
+      "SimpleTest START Loop " + TestRunner._currentLoop
+    );
+  }
+
+  TestRunner._urls = listURLs;
+  $("testframe").src = "";
+  TestRunner._checkForHangs();
+  TestRunner.runNextTest();
+};
+
+TestRunner.getNextUrl = function () {
+  var url = "";
+  // sometimes we have a subtest/harness which doesn't use a manifest
+  if (
+    TestRunner._urls[TestRunner._currentTest] instanceof Object &&
+    "test" in TestRunner._urls[TestRunner._currentTest]
+  ) {
+    url = TestRunner._urls[TestRunner._currentTest].test.url;
+    TestRunner.expected =
+      TestRunner._urls[TestRunner._currentTest].test.expected;
+  } else {
+    url = TestRunner._urls[TestRunner._currentTest];
+    TestRunner.expected = "pass";
+  }
+  return url;
+};
+
+/**
+ * Run the next test. If no test remains, calls onComplete().
+ **/
+TestRunner._haltTests = false;
+async function _runNextTest() {
+  if (
+    TestRunner._currentTest < TestRunner._urls.length &&
+    !TestRunner._haltTests
+  ) {
+    var url = TestRunner.getNextUrl();
+    TestRunner.currentTestURL = url;
+
+    $("current-test-path").innerHTML = url;
+
+    TestRunner._currentTestStartTimestamp = SpecialPowers.Cu.now();
+    TestRunner._currentTestStartTime = new Date().valueOf();
+    TestRunner._timeoutFactor = 1;
+    TestRunner._expectedMinAsserts = 0;
+    TestRunner._expectedMaxAsserts = 0;
+
+    TestRunner.structuredLogger.testStart(url);
+
+    if (TestRunner._urls[TestRunner._currentTest].test.allow_xul_xbl) {
+      await SpecialPowers.pushPermissions([
+        { type: "allowXULXBL", allow: true, context: "http://mochi.test:8888" },
+        { type: "allowXULXBL", allow: true, context: "http://example.org" },
+      ]);
+    }
+    TestRunner._makeIframe(url, 0);
+  } else {
+    $("current-test").innerHTML = "<b>Finished</b>";
+    // Only unload the last test to run if we're running more than one test.
+    if (TestRunner._urls.length > 1) {
+      TestRunner._makeIframe("about:blank", 0);
+    }
+
+    var passCount = parseInt($("pass-count").innerHTML, 10);
+    var failCount = parseInt($("fail-count").innerHTML, 10);
+    var todoCount = parseInt($("todo-count").innerHTML, 10);
+
+    if (passCount === 0 && failCount === 0 && todoCount === 0) {
+      // No |$('testframe').contentWindow|, so manually update: ...
+      // ... the log,
+      TestRunner.structuredLogger.error(
+        "TEST-UNEXPECTED-FAIL | SimpleTest/TestRunner.js | No checks actually run"
+      );
+      // ... the count,
+      $("fail-count").innerHTML = 1;
+      // ... the indicator.
+      var indicator = $("indicator");
+      indicator.innerHTML = "Status: Fail (No checks actually run)";
+      indicator.style.backgroundColor = "red";
+    }
+
+    let e10sMode = SpecialPowers.isMainProcess() ? "non-e10s" : "e10s";
+
+    TestRunner.structuredLogger.info("TEST-START | Shutdown");
+    TestRunner.structuredLogger.info("Passed:  " + passCount);
+    TestRunner.structuredLogger.info("Failed:  " + failCount);
+    TestRunner.structuredLogger.info("Todo:    " + todoCount);
+    TestRunner.structuredLogger.info("Mode:    " + e10sMode);
+    TestRunner.structuredLogger.info(
+      "Slowest: " +
+        TestRunner.slowestTestTime +
+        "ms - " +
+        TestRunner.slowestTestURL
+    );
+
+    // If we are looping, don't send this cause it closes the log file,
+    // also don't unregister the crash observers until we're done.
+    if (TestRunner.repeat === 0) {
+      SpecialPowers.unregisterProcessCrashObservers();
+      TestRunner.structuredLogger.info("SimpleTest FINISHED");
+    }
+
+    if (TestRunner.repeat === 0 && TestRunner.onComplete) {
+      TestRunner.onComplete();
+    }
+
+    if (
+      TestRunner._currentLoop <= TestRunner.repeat &&
+      !TestRunner._haltTests
+    ) {
+      TestRunner._currentLoop++;
+      TestRunner.resetTests(TestRunner._urls);
+      TestRunner._loopIsRestarting = true;
+    } else {
+      // Loops are finished
+      if (TestRunner.logEnabled) {
+        TestRunner.structuredLogger.info(
+          "TEST-INFO | Ran " + TestRunner._currentLoop + " Loops"
+        );
+        TestRunner.structuredLogger.info("SimpleTest FINISHED");
+      }
+
+      if (TestRunner.onComplete) {
+        TestRunner.onComplete();
+      }
+    }
+    TestRunner.generateFailureList();
+
+    if (TestRunner.jscovDirPrefix != "") {
+      coverageCollector.finalize();
+    }
+  }
+}
+TestRunner.runNextTest = _runNextTest;
+
+TestRunner.expectChildProcessCrash = function () {
+  TestRunner._expectingProcessCrash = true;
+};
+
+/**
+ * This stub is called by SimpleTest when a test is finished.
+ **/
+TestRunner.testFinished = function (tests) {
+  // Need to track subtests recorded here separately or else they'll
+  // trigger the `result after SimpleTest.finish()` error.
+  var extraTests = [];
+  var result = "OK";
+
+  // Prevent a test from calling finish() multiple times before we
+  // have a chance to unload it.
+  if (
+    TestRunner._currentTest == TestRunner._lastTestFinished &&
+    !TestRunner._loopIsRestarting
+  ) {
+    TestRunner.structuredLogger.testEnd(
+      TestRunner.currentTestURL,
+      "ERROR",
+      "OK",
+      "called finish() multiple times"
+    );
+    TestRunner.updateUI([{ result: false }]);
+    return;
+  }
+
+  if (TestRunner.jscovDirPrefix != "") {
+    coverageCollector.recordTestCoverage(TestRunner.currentTestURL);
+  }
+
+  SpecialPowers.requestDumpCoverageCounters().then(() => {
+    TestRunner._lastTestFinished = TestRunner._currentTest;
+    TestRunner._loopIsRestarting = false;
+
+    // TODO : replace this by a function that returns the mem data as an object
+    // that's dumped later with the test_end message
+    MemoryStats.dump(
+      TestRunner._currentTest,
+      TestRunner.currentTestURL,
+      TestRunner.dumpOutputDirectory,
+      TestRunner.dumpAboutMemoryAfterTest,
+      TestRunner.dumpDMDAfterTest
+    );
+
+    async function cleanUpCrashDumpFiles() {
+      if (
+        !(await SpecialPowers.removeExpectedCrashDumpFiles(
+          TestRunner._expectingProcessCrash
+        ))
+      ) {
+        let subtest = "expected-crash-dump-missing";
+        TestRunner.structuredLogger.testStatus(
+          TestRunner.currentTestURL,
+          subtest,
+          "ERROR",
+          "PASS",
+          "This test did not leave any crash dumps behind, but we were expecting some!"
+        );
+        extraTests.push({ name: subtest, result: false });
+        result = "ERROR";
+      }
+
+      var unexpectedCrashDumpFiles =
+        await SpecialPowers.findUnexpectedCrashDumpFiles();
+      TestRunner._expectingProcessCrash = false;
+      if (unexpectedCrashDumpFiles.length) {
+        let subtest = "unexpected-crash-dump-found";
+        TestRunner.structuredLogger.testStatus(
+          TestRunner.currentTestURL,
+          subtest,
+          "ERROR",
+          "PASS",
+          "This test left crash dumps behind, but we " +
+            "weren't expecting it to!",
+          null,
+          { unexpected_crashdump_files: unexpectedCrashDumpFiles }
+        );
+        extraTests.push({ name: subtest, result: false });
+        result = "CRASH";
+        unexpectedCrashDumpFiles.sort().forEach(function (aFilename) {
+          TestRunner.structuredLogger.info(
+            "Found unexpected crash dump file " + aFilename + "."
+          );
+        });
+      }
+
+      if (TestRunner.cleanupCrashes) {
+        if (await SpecialPowers.removePendingCrashDumpFiles()) {
+          TestRunner.structuredLogger.info(
+            "This test left pending crash dumps"
+          );
+        }
+      }
+    }
+
+    function runNextTest() {
+      if (TestRunner.currentTestURL != TestRunner.getLoadedTestURL()) {
+        TestRunner.structuredLogger.testStatus(
+          TestRunner.currentTestURL,
+          TestRunner.getLoadedTestURL(),
+          "FAIL",
+          "PASS",
+          "finished in a non-clean fashion, probably" +
+            " because it didn't call SimpleTest.finish()",
+          { loaded_test_url: TestRunner.getLoadedTestURL() }
+        );
+        extraTests.push({ name: "clean-finish", result: false });
+        result = result != "CRASH" ? "ERROR" : result;
+      }
+
+      SpecialPowers.addProfilerMarker(
+        "TestRunner",
+        { category: "Test", startTime: TestRunner._currentTestStartTimestamp },
+        TestRunner.currentTestURL
+      );
+      var runtime = new Date().valueOf() - TestRunner._currentTestStartTime;
+
+      TestRunner.structuredLogger.testEnd(
+        TestRunner.currentTestURL,
+        result,
+        "OK",
+        "Finished in " + runtime + "ms",
+        { runtime }
+      );
+
+      if (
+        TestRunner.slowestTestTime < runtime &&
+        TestRunner._timeoutFactor >= 1
+      ) {
+        TestRunner.slowestTestTime = runtime;
+        TestRunner.slowestTestURL = TestRunner.currentTestURL;
+      }
+
+      TestRunner.updateUI(tests.concat(extraTests));
+
+      // Don't show the interstitial if we just run one test with no repeats:
+      if (TestRunner._urls.length == 1 && TestRunner.repeat <= 1) {
+        TestRunner.testUnloaded();
+        return;
+      }
+
+      var interstitialURL;
+      if (
+        !testInXOriginFrame() &&
+        $("testframe").contentWindow.location.protocol == "chrome:"
+      ) {
+        interstitialURL = "tests/SimpleTest/iframe-between-tests.html";
+      } else {
+        interstitialURL = "/tests/SimpleTest/iframe-between-tests.html";
+      }
+      // check if there were test run after SimpleTest.finish, which should never happen
+      if (!testInXOriginFrame()) {
+        $("testframe").contentWindow.addEventListener("unload", function () {
+          var testwin = $("testframe").contentWindow;
+          if (
+            testwin.SimpleTest &&
+            testwin.SimpleTest._tests.length != testwin.SimpleTest.testsLength
+          ) {
+            var wrongtestlength =
+              testwin.SimpleTest._tests.length - testwin.SimpleTest.testsLength;
+            var wrongtestname = "";
+            for (var i = 0; i < wrongtestlength; i++) {
+              wrongtestname =
+                testwin.SimpleTest._tests[testwin.SimpleTest.testsLength + i]
+                  .name;
+              TestRunner.structuredLogger.error(
+                "TEST-UNEXPECTED-FAIL | " +
+                  TestRunner.currentTestURL +
+                  " logged result after SimpleTest.finish(): " +
+                  wrongtestname
+              );
+            }
+            TestRunner.updateUI([{ result: false }]);
+          }
+        });
+      }
+      TestRunner._makeIframe(interstitialURL, 0);
+    }
+
+    SpecialPowers.executeAfterFlushingMessageQueue(async function () {
+      await SpecialPowers.waitForCrashes(TestRunner._expectingProcessCrash);
+      await cleanUpCrashDumpFiles();
+      await SpecialPowers.flushPermissions();
+      await SpecialPowers.flushPrefEnv();
+      runNextTest();
+    });
+  });
+};
+
+/**
+ * This stub is called by XOrigin Tests to report assertion count.
+ **/
+TestRunner._xoriginAssertionCount = 0;
+TestRunner.addAssertionCount = function (count) {
+  if (!testInXOriginFrame()) {
+    TestRunner.error(
+      `addAssertionCount should only be called by a cross origin test`
+    );
+    return;
+  }
+
+  if (testInDifferentProcess()) {
+    TestRunner._xoriginAssertionCount += count;
+  }
+};
+
+TestRunner.testUnloaded = function () {
+  // If we're in a debug build, check assertion counts.  This code is
+  // similar to the code in Tester_nextTest in browser-test.js used
+  // for browser-chrome mochitests.
+  if (SpecialPowers.isDebugBuild) {
+    var newAssertionCount =
+      SpecialPowers.assertionCount() + TestRunner._xoriginAssertionCount;
+    var numAsserts = newAssertionCount - TestRunner._lastAssertionCount;
+    TestRunner._lastAssertionCount = newAssertionCount;
+
+    var max = TestRunner._expectedMaxAsserts;
+    var min = TestRunner._expectedMinAsserts;
+    if (Array.isArray(TestRunner.expected)) {
+      // Accumulate all assertion counts recorded in the failure pattern file.
+      let additionalAsserts = TestRunner.expected.reduce(
+        (acc, [pat, count]) => {
+          return pat == "ASSERTION" ? acc + count : acc;
+        },
+        0
+      );
+      min += additionalAsserts;
+      max += additionalAsserts;
+    }
+    TestRunner.structuredLogger.assertionCount(
+      TestRunner.currentTestURL,
+      numAsserts,
+      min,
+      max
+    );
+  }
+
+  // Always do this, so we can "reset" preferences between tests
+  SpecialPowers.comparePrefsToBaseline(
+    TestRunner.ignorePrefs,
+    TestRunner.verifyPrefsNextTest
+  );
+};
+
+TestRunner.verifyPrefsNextTest = function (p) {
+  if (TestRunner.comparePrefs) {
+    let prefs = Array.from(SpecialPowers.Cu.waiveXrays(p), x =>
+      SpecialPowers.unwrapIfWrapped(SpecialPowers.Cu.unwaiveXrays(x))
+    );
+    prefs.forEach(pr =>
+      TestRunner.structuredLogger.error(
+        "TEST-UNEXPECTED-FAIL | " +
+          TestRunner.currentTestURL +
+          " | changed preference: " +
+          pr
+      )
+    );
+  }
+  TestRunner.doNextTest();
+};
+
+TestRunner.doNextTest = function () {
+  TestRunner._currentTest++;
+  if (TestRunner.runSlower) {
+    setTimeout(TestRunner.runNextTest, 1000);
+  } else {
+    TestRunner.runNextTest();
+  }
+};
+
+/**
+ * Get the results.
+ */
+TestRunner.countResults = function (tests) {
+  var nOK = 0;
+  var nNotOK = 0;
+  var nTodo = 0;
+  for (var i = 0; i < tests.length; ++i) {
+    var test = tests[i];
+    if (test.todo && !test.result) {
+      nTodo++;
+    } else if (test.result && !test.todo) {
+      nOK++;
+    } else {
+      nNotOK++;
+    }
+  }
+  return { OK: nOK, notOK: nNotOK, todo: nTodo };
+};
+
+/**
+ * Print out table of any error messages found during looped run
+ */
+TestRunner.displayLoopErrors = function (tableName, tests) {
+  if (TestRunner.countResults(tests).notOK > 0) {
+    var table = $(tableName);
+    var curtest;
+    if (!table.rows.length) {
+      //if table headers are not yet generated, make them
+      var row = table.insertRow(table.rows.length);
+      var cell = row.insertCell(0);
+      var textNode = document.createTextNode("Test File Name:");
+      cell.appendChild(textNode);
+      cell = row.insertCell(1);
+      textNode = document.createTextNode("Test:");
+      cell.appendChild(textNode);
+      cell = row.insertCell(2);
+      textNode = document.createTextNode("Error message:");
+      cell.appendChild(textNode);
+    }
+
+    //find the broken test
+    for (var testnum in tests) {
+      curtest = tests[testnum];
+      if (
+        !(
+          (curtest.todo && !curtest.result) ||
+          (curtest.result && !curtest.todo)
+        )
+      ) {
+        //this is a failed test or the result of todo test. Display the related message
+        row = table.insertRow(table.rows.length);
+        cell = row.insertCell(0);
+        textNode = document.createTextNode(TestRunner.currentTestURL);
+        cell.appendChild(textNode);
+        cell = row.insertCell(1);
+        textNode = document.createTextNode(curtest.name);
+        cell.appendChild(textNode);
+        cell = row.insertCell(2);
+        textNode = document.createTextNode(curtest.diag ? curtest.diag : "");
+        cell.appendChild(textNode);
+      }
+    }
+  }
+};
+
+TestRunner.updateUI = function (tests) {
+  var results = TestRunner.countResults(tests);
+  var passCount = parseInt($("pass-count").innerHTML) + results.OK;
+  var failCount = parseInt($("fail-count").innerHTML) + results.notOK;
+  var todoCount = parseInt($("todo-count").innerHTML) + results.todo;
+  $("pass-count").innerHTML = passCount;
+  $("fail-count").innerHTML = failCount;
+  $("todo-count").innerHTML = todoCount;
+
+  // Set the top Green/Red bar
+  var indicator = $("indicator");
+  if (failCount > 0) {
+    indicator.innerHTML = "Status: Fail";
+    indicator.style.backgroundColor = "red";
+  } else if (passCount > 0) {
+    indicator.innerHTML = "Status: Pass";
+    indicator.style.backgroundColor = "#0d0";
+  } else {
+    indicator.innerHTML = "Status: ToDo";
+    indicator.style.backgroundColor = "orange";
+  }
+
+  // Set the table values
+  var trID = "tr-" + $("current-test-path").innerHTML;
+  var row = $(trID);
+
+  // Only update the row if it actually exists (autoUI)
+  if (row != null) {
+    var tds = row.getElementsByTagName("td");
+    tds[0].style.backgroundColor = "#0d0";
+    tds[0].innerHTML = parseInt(tds[0].innerHTML) + parseInt(results.OK);
+    tds[1].style.backgroundColor = results.notOK > 0 ? "red" : "#0d0";
+    tds[1].innerHTML = parseInt(tds[1].innerHTML) + parseInt(results.notOK);
+    tds[2].style.backgroundColor = results.todo > 0 ? "orange" : "#0d0";
+    tds[2].innerHTML = parseInt(tds[2].innerHTML) + parseInt(results.todo);
+  }
+
+  //if we ran in a loop, display any found errors
+  if (TestRunner.repeat > 0) {
+    TestRunner.displayLoopErrors("fail-table", tests);
+  }
+};
+
+// XOrigin Tests
+// If "--enable-xorigin-tests" is set, mochitests are run in a cross origin iframe.
+// The parent process will run at http://mochi.xorigin-test:8888", and individual
+// mochitests will be launched in a cross-origin iframe at http://mochi.test:8888.
+
+var xOriginDispatchMap = {
+  runner: TestRunner,
+  logger: TestRunner.structuredLogger,
+  addFailedTest: TestRunner.addFailedTest,
+  expectAssertions: TestRunner.expectAssertions,
+  expectChildProcessCrash: TestRunner.expectChildProcessCrash,
+  requestLongerTimeout: TestRunner.requestLongerTimeout,
+  "structuredLogger.deactivateBuffering":
+    TestRunner.structuredLogger.deactivateBuffering,
+  "structuredLogger.activateBuffering":
+    TestRunner.structuredLogger.activateBuffering,
+  "structuredLogger.testStatus": TestRunner.structuredLogger.testStatus,
+  "structuredLogger.info": TestRunner.structuredLogger.info,
+  "structuredLogger.warning": TestRunner.structuredLogger.warning,
+  "structuredLogger.error": TestRunner.structuredLogger.error,
+  testFinished: TestRunner.testFinished,
+  addAssertionCount: TestRunner.addAssertionCount,
+};
+
+function xOriginTestRunnerHandler(event) {
+  if (event.data.harnessType != "SimpleTest") {
+    return;
+  }
+  // Handles messages from xOriginRunner in SimpleTest.js.
+  if (event.data.command in xOriginDispatchMap) {
+    xOriginDispatchMap[event.data.command].apply(
+      xOriginDispatchMap[event.data.applyOn],
+      event.data.params
+    );
+  } else {
+    TestRunner.error(`Command ${event.data.command} not found
+      in xOriginDispatchMap`);
+  }
+}
+
+TestRunner.setXOriginEventHandler = function () {
+  window.addEventListener("message", xOriginTestRunnerHandler);
+};
diff --git a/testing/mochitest/tests/SimpleTest/WindowSnapshot.js b/testing/mochitest/tests/SimpleTest/WindowSnapshot.js
new file mode 100644
index 0000000000..d1925f36e6
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/WindowSnapshot.js
@@ -0,0 +1,122 @@
+var gWindowUtils;
+
+try {
+  gWindowUtils = SpecialPowers.getDOMWindowUtils(window);
+  if (gWindowUtils && !gWindowUtils.compareCanvases) {
+    gWindowUtils = null;
+  }
+} catch (e) {
+  gWindowUtils = null;
+}
+
+function snapshotWindow(win, withCaret) {
+  return SpecialPowers.snapshotWindow(win, withCaret);
+}
+
+function snapshotRect(win, rect) {
+  return SpecialPowers.snapshotRect(win, rect);
+}
+
+// If the two snapshots don't compare as expected (true for equal, false for
+// unequal), returns their serializations as data URIs.  In all cases, returns
+// whether the comparison was as expected.
+function compareSnapshots(s1, s2, expectEqual, fuzz) {
+  if (s1.width != s2.width || s1.height != s2.height) {
+    ok(
+      false,
+      "Snapshot canvases are not the same size: " +
+        s1.width +
+        "x" +
+        s1.height +
+        " vs. " +
+        s2.width +
+        "x" +
+        s2.height
+    );
+    return [false];
+  }
+  var passed = false;
+  var numDifferentPixels;
+  var maxDifference = { value: undefined };
+  if (gWindowUtils) {
+    var equal;
+    try {
+      numDifferentPixels = gWindowUtils.compareCanvases(s1, s2, maxDifference);
+      if (!fuzz) {
+        equal = numDifferentPixels == 0;
+      } else {
+        equal =
+          numDifferentPixels <= fuzz.numDifferentPixels &&
+          maxDifference.value <= fuzz.maxDifference;
+      }
+      passed = equal == expectEqual;
+    } catch (e) {
+      ok(false, "Exception thrown from compareCanvases: " + e);
+    }
+  }
+
+  var s1DataURI, s2DataURI;
+  if (!passed) {
+    s1DataURI = s1.toDataURL();
+    s2DataURI = s2.toDataURL();
+
+    if (!gWindowUtils) {
+      passed = (s1DataURI == s2DataURI) == expectEqual;
+    }
+  }
+
+  return [
+    passed,
+    s1DataURI,
+    s2DataURI,
+    numDifferentPixels,
+    maxDifference.value,
+  ];
+}
+
+function assertSnapshots(s1, s2, expectEqual, fuzz, s1name, s2name) {
+  var [passed, s1DataURI, s2DataURI, numDifferentPixels, maxDifference] =
+    compareSnapshots(s1, s2, expectEqual, fuzz);
+  var sym = expectEqual ? "==" : "!=";
+  ok(passed, "reftest comparison: " + sym + " " + s1name + " " + s2name);
+  if (!passed) {
+    let status = "TEST-UNEXPECTED-FAIL";
+    if (usesFailurePatterns() && recordIfMatchesFailurePattern(s1name)) {
+      status = "TEST-KNOWN-FAIL";
+    }
+    // The language / format in this message should match the failure messages
+    // displayed by reftest.js's "RecordResult()" method so that log output
+    // can be parsed by reftest-analyzer.xhtml
+    var report =
+      "REFTEST " +
+      status +
+      " | " +
+      s1name +
+      " | image comparison (" +
+      sym +
+      "), max difference: " +
+      maxDifference +
+      ", number of differing pixels: " +
+      numDifferentPixels +
+      "\n";
+    if (expectEqual) {
+      report += "REFTEST   IMAGE 1 (TEST): " + s1DataURI + "\n";
+      report += "REFTEST   IMAGE 2 (REFERENCE): " + s2DataURI + "\n";
+    } else {
+      report += "REFTEST   IMAGE: " + s1DataURI + "\n";
+    }
+    (info || dump)(report);
+  }
+  return passed;
+}
+
+function assertWindowPureColor(win, color) {
+  const snapshot = SpecialPowers.snapshotRect(win);
+  const canvas = document.createElement("canvas");
+  canvas.width = snapshot.width;
+  canvas.height = snapshot.height;
+  const context = canvas.getContext("2d");
+  context.fillStyle = color;
+  context.fillRect(0, 0, canvas.width, canvas.height);
+  assertSnapshots(snapshot, canvas, true, null, "snapshot", color);
+}
diff --git a/testing/mochitest/tests/SimpleTest/WorkerHandler.js b/testing/mochitest/tests/SimpleTest/WorkerHandler.js
new file mode 100644
index 0000000000..7794087805
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/WorkerHandler.js
@@ -0,0 +1,46 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Sets the worker message and error event handlers to respond to SimpleTest
+ * style messages.
+ */
+function listenForTests(worker, opts = { verbose: true }) {
+  worker.onerror = function (error) {
+    error.preventDefault();
+    ok(false, "Worker error " + error.message);
+  };
+  worker.onmessage = function (msg) {
+    if (opts && opts.verbose) {
+      ok(true, "MAIN: onmessage " + JSON.stringify(msg.data));
+    }
+    switch (msg.data.kind) {
+      case "is":
+        SimpleTest.ok(
+          msg.data.outcome,
+          msg.data.description + "( " + msg.data.a + " ==? " + msg.data.b + ")"
+        );
+        return;
+      case "isnot":
+        SimpleTest.ok(
+          msg.data.outcome,
+          msg.data.description + "( " + msg.data.a + " !=? " + msg.data.b + ")"
+        );
+        return;
+      case "ok":
+        SimpleTest.ok(msg.data.condition, msg.data.description);
+        return;
+      case "info":
+        SimpleTest.info(msg.data.description);
+        return;
+      case "finish":
+        SimpleTest.finish();
+        return;
+      default:
+        SimpleTest.ok(
+          false,
+          "test_osfile.xul: wrong message " + JSON.stringify(msg.data)
+        );
+    }
+  };
+}
diff --git a/testing/mochitest/tests/SimpleTest/WorkerSimpleTest.js b/testing/mochitest/tests/SimpleTest/WorkerSimpleTest.js
new file mode 100644
index 0000000000..ce4848d7af
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/WorkerSimpleTest.js
@@ -0,0 +1,44 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function log(text) {
+  dump("WORKER " + text + "\n");
+}
+
+function send(message) {
+  self.postMessage(message);
+}
+
+function finish() {
+  send({ kind: "finish" });
+}
+
+function ok(condition, description) {
+  send({ kind: "ok", condition: !!condition, description: "" + description });
+}
+
+function is(a, b, description) {
+  let outcome = a == b; // Need to decide outcome here, as not everything can be serialized
+  send({
+    kind: "is",
+    outcome,
+    description: "" + description,
+    a: "" + a,
+    b: "" + b,
+  });
+}
+
+function isnot(a, b, description) {
+  let outcome = a != b; // Need to decide outcome here, as not everything can be serialized
+  send({
+    kind: "isnot",
+    outcome,
+    description: "" + description,
+    a: "" + a,
+    b: "" + b,
+  });
+}
+
+function info(description) {
+  send({ kind: "info", description: "" + description });
+}
diff --git a/testing/mochitest/tests/SimpleTest/iframe-between-tests.html b/testing/mochitest/tests/SimpleTest/iframe-between-tests.html
new file mode 100644
index 0000000000..8de879f205
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/iframe-between-tests.html
@@ -0,0 +1,17 @@
+<title>iframe for between tests</title>
+<!--
+  This page exists so that our accounting for assertions correctly
+  counts assertions that happen while leaving a page.  We load this page
+  after a test finishes, check the assertion counts, and then go on to
+  load the next.
+-->
+<script>
+window.addEventListener("load", function() {
+  var runner = (parent.TestRunner || parent.wrappedJSObject.TestRunner);
+  runner.testUnloaded();
+
+  if (SpecialPowers) {
+    SpecialPowers.DOMWindowUtils.runNextCollectorTimer();
+  }
+});
+</script>
diff --git a/testing/mochitest/tests/SimpleTest/moz.build b/testing/mochitest/tests/SimpleTest/moz.build
new file mode 100644
index 0000000000..55c54e6255
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/moz.build
@@ -0,0 +1,27 @@
+# -*- 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/.
+
+TEST_HARNESS_FILES.testing.mochitest.tests.SimpleTest += [
+    "/docshell/test/chrome/docshell_helpers.js",
+    "AccessibilityUtils.js",
+    "ChromeTask.js",
+    "EventUtils.js",
+    "ExtensionTestUtils.js",
+    "iframe-between-tests.html",
+    "LogController.js",
+    "MemoryStats.js",
+    "MockObjects.js",
+    "MozillaLogger.js",
+    "NativeKeyCodes.js",
+    "paint_listener.js",
+    "setup.js",
+    "SimpleTest.js",
+    "test.css",
+    "TestRunner.js",
+    "WindowSnapshot.js",
+    "WorkerHandler.js",
+    "WorkerSimpleTest.js",
+]
diff --git a/testing/mochitest/tests/SimpleTest/paint_listener.js b/testing/mochitest/tests/SimpleTest/paint_listener.js
new file mode 100644
index 0000000000..2fc6ab425a
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/paint_listener.js
@@ -0,0 +1,109 @@
+(function () {
+  var accumulatedRect = null;
+  var onpaint = [];
+  var debug = SpecialPowers.getBoolPref("testing.paint_listener.debug", false);
+  const FlushModes = {
+    FLUSH: 0,
+    NOFLUSH: 1,
+  };
+
+  function paintListener(event) {
+    if (event.target != window) {
+      if (debug) {
+        dump("got MozAfterPaint for wrong window\n");
+      }
+      return;
+    }
+    var clientRect = event.boundingClientRect;
+    var eventRect;
+    if (clientRect) {
+      eventRect = [
+        clientRect.left,
+        clientRect.top,
+        clientRect.right,
+        clientRect.bottom,
+      ];
+    } else {
+      eventRect = [0, 0, 0, 0];
+    }
+    if (debug) {
+      dump("got MozAfterPaint: " + eventRect.join(",") + "\n");
+    }
+    accumulatedRect = accumulatedRect
+      ? [
+          Math.min(accumulatedRect[0], eventRect[0]),
+          Math.min(accumulatedRect[1], eventRect[1]),
+          Math.max(accumulatedRect[2], eventRect[2]),
+          Math.max(accumulatedRect[3], eventRect[3]),
+        ]
+      : eventRect;
+    if (debug) {
+      dump("Dispatching " + onpaint.length + " onpaint listeners\n");
+    }
+    while (onpaint.length) {
+      window.setTimeout(onpaint.pop(), 0);
+    }
+  }
+  window.addEventListener("MozAfterPaint", paintListener);
+
+  function waitForPaints(callback, subdoc, flushMode) {
+    // Wait until paint suppression has ended
+    var utils = SpecialPowers.getDOMWindowUtils(window);
+    if (utils.paintingSuppressed) {
+      if (debug) {
+        dump("waiting for paint suppression to end...\n");
+      }
+      window.setTimeout(function () {
+        waitForPaints(callback, subdoc, flushMode);
+      }, 0);
+      return;
+    }
+
+    // The call to getBoundingClientRect will flush pending layout
+    // notifications. Sometimes, however, this is undesirable since it can mask
+    // bugs where the code under test should be performing the flush.
+    if (flushMode === FlushModes.FLUSH) {
+      document.documentElement.getBoundingClientRect();
+      if (subdoc) {
+        subdoc.documentElement.getBoundingClientRect();
+      }
+    }
+
+    if (utils.isMozAfterPaintPending) {
+      if (debug) {
+        dump("waiting for paint...\n");
+      }
+      onpaint.push(function () {
+        waitForPaints(callback, subdoc, FlushModes.NOFLUSH);
+      });
+      if (utils.isTestControllingRefreshes) {
+        utils.advanceTimeAndRefresh(0);
+      }
+      return;
+    }
+
+    if (debug) {
+      dump("done...\n");
+    }
+    var result = accumulatedRect || [0, 0, 0, 0];
+    accumulatedRect = null;
+    callback.apply(null, result);
+  }
+
+  window.waitForAllPaintsFlushed = function (callback, subdoc) {
+    waitForPaints(callback, subdoc, FlushModes.FLUSH);
+  };
+
+  window.waitForAllPaints = function (callback) {
+    waitForPaints(callback, null, FlushModes.NOFLUSH);
+  };
+
+  window.promiseAllPaintsDone = function (subdoc = null, flush = false) {
+    var flushmode = flush ? FlushModes.FLUSH : FlushModes.NOFLUSH;
+    return new Promise(function (resolve, reject) {
+      // The callback is given the components of the rect, but resolve() can
+      // only be given one arg, so we turn it back into an array.
+      waitForPaints((l, r, t, b) => resolve([l, r, t, b]), subdoc, flushmode);
+    });
+  };
+})();
diff --git a/testing/mochitest/tests/SimpleTest/setup.js b/testing/mochitest/tests/SimpleTest/setup.js
new file mode 100644
index 0000000000..0dd4770c0b
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/setup.js
@@ -0,0 +1,383 @@
+/* -*- js-indent-level: 2; indent-tabs-mode: nil -*- */
+/* vim:set ts=2 sw=2 sts=2 et: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+// This file expects the following files to be loaded.
+/* import-globals-from TestRunner.js */
+
+// From the harness:
+/* import-globals-from ../../chrome-harness.js */
+/* import-globals-from ../../chunkifyTests.js */
+
+// It appears we expect these from one of the MochiKit scripts.
+/* global toggleElementClass, removeElementClass, addElementClass,
+          hasElementClass */
+
+TestRunner.logEnabled = true;
+TestRunner.logger = LogController;
+
+if (!("SpecialPowers" in window)) {
+  dump("SimpleTest setup.js found SpecialPowers unavailable: reloading...\n");
+  setTimeout(() => {
+    window.location.reload();
+  }, 1000);
+}
+
+/* Helper function */
+function parseQueryString(encodedString, useArrays) {
+  // strip a leading '?' from the encoded string
+  var qstr =
+    encodedString.length && encodedString[0] == "?"
+      ? encodedString.substring(1)
+      : encodedString;
+  var pairs = qstr.replace(/\+/g, "%20").split(/(\&amp\;|\&\#38\;|\&#x26;|\&)/);
+  var o = {};
+  var decode;
+  if (typeof decodeURIComponent != "undefined") {
+    decode = decodeURIComponent;
+  } else {
+    decode = unescape;
+  }
+  if (useArrays) {
+    for (var i = 0; i < pairs.length; i++) {
+      var pair = pairs[i].split("=");
+      if (pair.length !== 2) {
+        continue;
+      }
+      var name = decode(pair[0]);
+      var arr = o[name];
+      if (!(arr instanceof Array)) {
+        arr = [];
+        o[name] = arr;
+      }
+      arr.push(decode(pair[1]));
+    }
+  } else {
+    for (i = 0; i < pairs.length; i++) {
+      pair = pairs[i].split("=");
+      if (pair.length !== 2) {
+        continue;
+      }
+      o[decode(pair[0])] = decode(pair[1]);
+    }
+  }
+  return o;
+}
+
+/* helper function, specifically for prefs to ignore */
+function loadFile(url, callback) {
+  let req = new XMLHttpRequest();
+  req.open("GET", url);
+  req.onload = function () {
+    if (req.readyState == 4) {
+      if (req.status == 200) {
+        try {
+          let prefs = JSON.parse(req.responseText);
+          callback(prefs);
+        } catch (e) {
+          dump(
+            "TEST-UNEXPECTED-FAIL: setup.js | error parsing " +
+              url +
+              " (" +
+              e +
+              ")\n"
+          );
+          throw e;
+        }
+      } else {
+        dump(
+          "TEST-UNEXPECTED-FAIL: setup.js | error loading " +
+            url +
+            " (HTTP " +
+            req.status +
+            ")\n"
+        );
+        callback({});
+      }
+    }
+  };
+  req.send();
+}
+
+// Check the query string for arguments
+var params = parseQueryString(location.search.substring(1), true);
+
+var config = {};
+if (window.readConfig) {
+  config = readConfig();
+}
+
+if (config.testRoot == "chrome" || config.testRoot == "a11y") {
+  for (var p in params) {
+    // Compare with arrays to find boolean equivalents, since that's what
+    // |parseQueryString| with useArrays returns.
+    if (params[p] == [1]) {
+      config[p] = true;
+    } else if (params[p] == [0]) {
+      config[p] = false;
+    } else {
+      config[p] = params[p];
+    }
+  }
+  params = config;
+  params.baseurl = "chrome://mochitests/content";
+} else if (params.xOriginTests) {
+  params.baseurl = "http://mochi.test:8888/tests/";
+} else {
+  params.baseurl = "";
+}
+
+if (params.testRoot == "browser") {
+  params.testPrefix = "chrome://mochitests/content/browser/";
+} else if (params.testRoot == "chrome") {
+  params.testPrefix = "chrome://mochitests/content/chrome/";
+} else if (params.testRoot == "a11y") {
+  params.testPrefix = "chrome://mochitests/content/a11y/";
+} else if (params.xOriginTests) {
+  params.testPrefix = "http://mochi.test:8888/tests/";
+  params.httpsBaseUrl = "https://example.org:443/tests/";
+} else {
+  params.testPrefix = "/tests/";
+}
+
+// set the per-test timeout if specified in the query string
+if (params.timeout) {
+  TestRunner.timeout = parseInt(params.timeout) * 1000;
+}
+
+// log levels for console and logfile
+var fileLevel = params.fileLevel || null;
+var consoleLevel = params.consoleLevel || null;
+
+// repeat tells us how many times to repeat the tests
+if (params.repeat) {
+  TestRunner.repeat = params.repeat;
+}
+
+if (params.runUntilFailure) {
+  TestRunner.runUntilFailure = true;
+}
+
+// closeWhenDone tells us to close the browser when complete
+if (params.closeWhenDone) {
+  TestRunner.onComplete = SpecialPowers.quit.bind(SpecialPowers);
+}
+
+if (params.failureFile) {
+  TestRunner.setFailureFile(params.failureFile);
+}
+
+// Breaks execution and enters the JS debugger on a test failure
+if (params.debugOnFailure) {
+  TestRunner.debugOnFailure = true;
+}
+
+// logFile to write our results
+if (params.logFile) {
+  var mfl = new MozillaFileLogger(params.logFile);
+  TestRunner.logger.addListener("mozLogger", fileLevel + "", mfl.logCallback);
+}
+
+// A temporary hack for android 4.0 where Fennec utilizes the pandaboard so much it reboots
+if (params.runSlower) {
+  TestRunner.runSlower = true;
+}
+
+if (params.dumpOutputDirectory) {
+  TestRunner.dumpOutputDirectory = params.dumpOutputDirectory;
+}
+
+if (params.dumpAboutMemoryAfterTest) {
+  TestRunner.dumpAboutMemoryAfterTest = true;
+}
+
+if (params.dumpDMDAfterTest) {
+  TestRunner.dumpDMDAfterTest = true;
+}
+
+if (params.interactiveDebugger) {
+  TestRunner.interactiveDebugger = true;
+}
+
+if (params.jscovDirPrefix) {
+  TestRunner.jscovDirPrefix = params.jscovDirPrefix;
+}
+
+if (params.maxTimeouts) {
+  TestRunner.maxTimeouts = params.maxTimeouts;
+}
+
+if (params.cleanupCrashes) {
+  TestRunner.cleanupCrashes = true;
+}
+
+if (params.xOriginTests) {
+  TestRunner.xOriginTests = true;
+  TestRunner.setXOriginEventHandler();
+}
+
+if (params.timeoutAsPass) {
+  TestRunner.timeoutAsPass = true;
+}
+
+if (params.conditionedProfile) {
+  TestRunner.conditionedProfile = true;
+}
+
+if (params.comparePrefs) {
+  TestRunner.comparePrefs = true;
+}
+
+// Log things to the console if appropriate.
+TestRunner.logger.addListener(
+  "dumpListener",
+  consoleLevel + "",
+  function (msg) {
+    dump(msg.info.join(" ") + "\n");
+  }
+);
+
+var gTestList = [];
+var RunSet = {};
+
+RunSet.runall = function (e) {
+  // Filter tests to include|exclude tests based on data in params.filter.
+  // This allows for including or excluding tests from the gTestList
+  // TODO Only used by ipc tests, remove once those are implemented sanely
+  if (params.testManifest) {
+    getTestManifest(
+      getTestManifestURL(params.testManifest),
+      params,
+      function (filter) {
+        gTestList = filterTests(filter, gTestList, params.runOnly);
+        RunSet.runtests();
+      }
+    );
+  } else {
+    RunSet.runtests();
+  }
+};
+
+RunSet.runtests = function (e) {
+  // Which tests we're going to run
+  var my_tests = gTestList;
+
+  if (params.startAt || params.endAt) {
+    my_tests = skipTests(my_tests, params.startAt, params.endAt);
+  }
+
+  if (params.shuffle) {
+    for (var i = my_tests.length - 1; i > 0; --i) {
+      var j = Math.floor(Math.random() * i);
+      var tmp = my_tests[j];
+      my_tests[j] = my_tests[i];
+      my_tests[i] = tmp;
+    }
+  }
+  TestRunner.setParameterInfo(params);
+  TestRunner.runTests(my_tests);
+};
+
+RunSet.reloadAndRunAll = function (e) {
+  e.preventDefault();
+  //window.location.hash = "";
+  if (params.autorun) {
+    window.location.search += "";
+    // eslint-disable-next-line no-self-assign
+    window.location.href = window.location.href;
+  } else if (window.location.search) {
+    window.location.href += "&autorun=1";
+  } else {
+    window.location.href += "?autorun=1";
+  }
+};
+
+// UI Stuff
+function toggleVisible(elem) {
+  toggleElementClass("invisible", elem);
+}
+
+function makeVisible(elem) {
+  removeElementClass(elem, "invisible");
+}
+
+function makeInvisible(elem) {
+  addElementClass(elem, "invisible");
+}
+
+function isVisible(elem) {
+  // you may also want to check for
+  // getElement(elem).style.display == "none"
+  return !hasElementClass(elem, "invisible");
+}
+
+function toggleNonTests(e) {
+  e.preventDefault();
+  var elems = document.getElementsByClassName("non-test");
+  for (var i = "0"; i < elems.length; i++) {
+    toggleVisible(elems[i]);
+  }
+  if (isVisible(elems[0])) {
+    $("toggleNonTests").innerHTML = "Hide Non-Tests";
+  } else {
+    $("toggleNonTests").innerHTML = "Show Non-Tests";
+  }
+}
+
+// hook up our buttons
+function hookup() {
+  if (params.manifestFile) {
+    getTestManifest(
+      getTestManifestURL(params.manifestFile),
+      params,
+      hookupTests
+    );
+  } else {
+    hookupTests(gTestList);
+  }
+}
+
+function getPrefList() {
+  if (params.ignorePrefsFile) {
+    loadFile(getTestManifestURL(params.ignorePrefsFile), function (prefs) {
+      TestRunner.ignorePrefs = prefs;
+      RunSet.runall();
+    });
+  } else {
+    RunSet.runall();
+  }
+}
+
+function hookupTests(testList) {
+  if (testList.length) {
+    gTestList = testList;
+  } else {
+    gTestList = [];
+    for (var obj in testList) {
+      gTestList.push(testList[obj]);
+    }
+  }
+
+  document.getElementById("runtests").onclick = RunSet.reloadAndRunAll;
+  document.getElementById("toggleNonTests").onclick = toggleNonTests;
+  // run automatically if autorun specified
+  if (params.autorun) {
+    getPrefList();
+  }
+}
+
+function getTestManifestURL(path) {
+  // The test manifest url scheme should be the same protocol as the containing
+  // window... unless it's not http(s)
+  if (
+    window.location.protocol == "http:" ||
+    window.location.protocol == "https:"
+  ) {
+    return window.location.protocol + "//" + window.location.host + "/" + path;
+  }
+  return "http://mochi.test:8888/" + path;
+}
diff --git a/testing/mochitest/tests/SimpleTest/test.css b/testing/mochitest/tests/SimpleTest/test.css
new file mode 100644
index 0000000000..357070e8ae
--- /dev/null
+++ b/testing/mochitest/tests/SimpleTest/test.css
@@ -0,0 +1,39 @@
+.test_ok {
+  color: #0d0;
+  display: none;
+}
+
+.test_not_ok {
+  color: red;
+  display: block;
+}
+
+.test_todo {
+  /* color: orange; */
+  display: block;
+}
+
+.test_ok, .test_not_ok, .test_todo {
+  border-bottom-width: 2px;
+  border-bottom-style: solid;
+  border-bottom-color: black;
+}
+
+.all_pass {
+  background-color: #0d0;
+}
+
+.some_fail {
+  background-color: red;
+}
+
+.todo_only {
+  background-color: orange;
+}
+
+.tests_report {
+  border-width: 2px;
+  border-style: solid;
+  width: 20em;
+  display: table;
+}