Adding upstream version 124.0.1.upstream/124.0.1

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

17 files changed, 5509 insertions, 0 deletions

diff --git a/testing/specialpowers/Makefile.in b/testing/specialpowers/Makefile.in
new file mode 100644
index 0000000000..e42d0650ef
--- /dev/null
+++ b/testing/specialpowers/Makefile.in
@@ -0,0 +1,6 @@
+#
+# 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/.
+
+XPI_PKGNAME = specialpowers@mozilla.org
diff --git a/testing/specialpowers/api.js b/testing/specialpowers/api.js
new file mode 100644
index 0000000000..a0ffe42b32
--- /dev/null
+++ b/testing/specialpowers/api.js
@@ -0,0 +1,68 @@
+/* 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/. */
+
+/* globals ExtensionAPI, Services, XPCOMUtils */
+
+ChromeUtils.defineESModuleGetters(this, {
+  SpecialPowersParent: "resource://testing-common/SpecialPowersParent.sys.mjs",
+});
+
+XPCOMUtils.defineLazyServiceGetter(
+  this,
+  "resProto",
+  "@mozilla.org/network/protocol;1?name=resource",
+  "nsISubstitutingProtocolHandler"
+);
+
+this.specialpowers = class extends ExtensionAPI {
+  onStartup() {
+    // Register special testing modules.
+    let manifest = Services.dirsvc.get("ProfD", Ci.nsIFile);
+    manifest.append("tests.manifest");
+    Components.manager
+      .QueryInterface(Ci.nsIComponentRegistrar)
+      .autoRegister(manifest);
+
+    {
+      let uri = Services.io.newURI("content/", null, this.extension.rootURI);
+      resProto.setSubstitutionWithFlags(
+        "specialpowers",
+        uri,
+        resProto.ALLOW_CONTENT_ACCESS
+      );
+    }
+
+    if (!resProto.hasSubstitution("testing-common")) {
+      let uri = Services.io.newURI("modules/", null, this.extension.rootURI);
+      resProto.setSubstitution(
+        "testing-common",
+        uri,
+        resProto.ALLOW_CONTENT_ACCESS
+      );
+    }
+
+    SpecialPowersParent.registerActor();
+
+    ChromeUtils.registerWindowActor("AppTestDelegate", {
+      parent: {
+        esModuleURI: "resource://specialpowers/AppTestDelegateParent.sys.mjs",
+      },
+      child: {
+        esModuleURI: "resource://specialpowers/AppTestDelegateChild.sys.mjs",
+        events: {
+          DOMContentLoaded: { capture: true },
+          load: { capture: true },
+        },
+      },
+      allFrames: true,
+      includeChrome: true,
+    });
+  }
+
+  onShutdown() {
+    SpecialPowersParent.unregisterActor();
+    ChromeUtils.unregisterWindowActor("AppTestDelegate");
+    resProto.setSubstitution("specialpowers", null);
+  }
+};
diff --git a/testing/specialpowers/content/AppTestDelegate.sys.mjs b/testing/specialpowers/content/AppTestDelegate.sys.mjs
new file mode 100644
index 0000000000..e2c2b60daf
--- /dev/null
+++ b/testing/specialpowers/content/AppTestDelegate.sys.mjs
@@ -0,0 +1,89 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * This file offers the test helpers that are directly exposed to mochitests.
+ * Their implementations are in app-specific "AppUiTestDelegate.sys.mjs" files.
+ *
+ * For documentation, see AppTestDelegateParent.sys.mjs.
+ * For documentation on the methods of AppUiTestDelegate, see below.
+ */
+
+class AppTestDelegateImplementation {
+  actor(window) {
+    return window.windowGlobalChild.getActor("AppTestDelegate");
+  }
+
+  /**
+   * Click on the pageAction button, to open its popup, or to trigger
+   * pageAction.onClicked if there is no popup.
+   */
+  clickPageAction(window, extension) {
+    return this.actor(window).sendQuery("clickPageAction", {
+      extensionId: extension.id,
+    });
+  }
+
+  /**
+   * Click on the browserAction button, to open its popup, or to trigger
+   * browserAction.onClicked if there is no popup.
+   */
+  clickBrowserAction(window, extension) {
+    return this.actor(window).sendQuery("clickBrowserAction", {
+      extensionId: extension.id,
+    });
+  }
+
+  /**
+   * Close the browserAction popup, if any.
+   * Do not use this for pageAction popups, use closePageAction instead.
+   */
+  closeBrowserAction(window, extension) {
+    return this.actor(window).sendQuery("closeBrowserAction", {
+      extensionId: extension.id,
+    });
+  }
+
+  /**
+   * Close the pageAction popup, if any.
+   * Do not use this for browserAction popups, use closeBrowserAction instead.
+   */
+  closePageAction(window, extension) {
+    return this.actor(window).sendQuery("closePageAction", {
+      extensionId: extension.id,
+    });
+  }
+
+  /**
+   * Wait for the pageAction or browserAction/action popup panel to open.
+   * This must be called BEFORE any attempt to open the popup.
+   */
+  awaitExtensionPanel(window, extension) {
+    return this.actor(window).sendQuery("awaitExtensionPanel", {
+      extensionId: extension.id,
+    });
+  }
+
+  /**
+   * Open a tab with the given url in the given window.
+   * Returns an opaque object that can be passed to AppTestDelegate.removeTab.
+   */
+  async openNewForegroundTab(window, url, waitForLoad = true) {
+    const tabId = await this.actor(window).sendQuery("openNewForegroundTab", {
+      url,
+      waitForLoad,
+    });
+    // Note: this id is only meaningful to AppTestDelegate and independent of
+    // any other concept of "tab id".
+    return { id: tabId };
+  }
+
+  /**
+   * Close a tab opened by AppTestDelegate.openNewForegroundTab.
+   */
+  removeTab(window, tab) {
+    return this.actor(window).sendQuery("removeTab", { tabId: tab.id });
+  }
+}
+
+export var AppTestDelegate = new AppTestDelegateImplementation();
diff --git a/testing/specialpowers/content/AppTestDelegateChild.sys.mjs b/testing/specialpowers/content/AppTestDelegateChild.sys.mjs
new file mode 100644
index 0000000000..1d78d41f5d
--- /dev/null
+++ b/testing/specialpowers/content/AppTestDelegateChild.sys.mjs
@@ -0,0 +1,18 @@
+/* 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/. */
+
+export class AppTestDelegateChild extends JSWindowActorChild {
+  handleEvent(event) {
+    switch (event.type) {
+      case "DOMContentLoaded":
+      case "load": {
+        this.sendAsyncMessage(event.type, {
+          internalURL: event.target.documentURI,
+          visibleURL: event.target.location?.href,
+        });
+        break;
+      }
+    }
+  }
+}
diff --git a/testing/specialpowers/content/AppTestDelegateParent.sys.mjs b/testing/specialpowers/content/AppTestDelegateParent.sys.mjs
new file mode 100644
index 0000000000..b271dea3df
--- /dev/null
+++ b/testing/specialpowers/content/AppTestDelegateParent.sys.mjs
@@ -0,0 +1,135 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * This module provides the bridge between the "AppTestDelegate" helper in
+ * mochitests and the supporting implementations in AppUiTestDelegate.sys.mjs.
+ *
+ * "AppTestDelegate" is documented in AppTestDelegate.sys.mjs and enables
+ * mochitests to invoke common functionality whose implementation is different
+ * (e.g. in browser/ and mobile/ instead of toolkit/).
+ * Tests can use this common interface after importing AppTestDelegate.sys.mjs:
+ *
+ *     // head.js, in the scope of a plain mochitest:
+ *     var { AppTestDelegate } = SpecialPowers.ChromeUtils.importESModule(
+ *       "resource://specialpowers/AppTestDelegate.sys.mjs"
+ *     );
+ *
+ *     // test usage example: open and close a tab.
+ *     let tab = await AppTestDelegate.openNewForegroundTab(window, url);
+ *     await AppTestDelegate.removeTab(window, tab);
+ *
+ * ## Overview of files supporting "AppTestDelegate":
+ *
+ * MOZ_BUILD_APP-specific AppUiTestDelegate.sys.mjs implementations:
+ * - browser/components/extensions/test/AppUiTestDelegate.jsm
+ * - mobile/android/modules/test/AppUiTestDelegate.jsm
+ * - mail/components/extensions/test/AppUiTestDelegate.sys.mjs (in comm-central)
+ *
+ * Glue between AppUiTestDelegate.sys.mjs in parent and test code in child:
+ * - testing/specialpowers/content/AppTestDelegateParent.sys.mjs (this file)
+ * - testing/specialpowers/content/AppTestDelegateChild.sys.mjs
+ * - testing/specialpowers/content/AppTestDelegate.sys.mjs
+ *
+ * Setup for usage by test code in child (i.e. plain mochitests):
+ * - Import AppTestDelegate.sys.mjs (e.g. in head.js or the test)
+ *
+ * Note: some browser-chrome tests import AppUiTestDelegate.sys.mjs directly,
+ * but that is not part of this API contract. They merely reuse code.
+ *
+ * ## How to add new AppTestDelegate methods
+ *
+ * - Add the method to AppTestDelegate.sys.mjs
+ * - Add a message forwarder in AppTestDelegateChild.sys.mjs
+ * - Add a message handler in AppTestDelegateParent.sys.mjs
+ * - Add an implementation in AppUiTestDelegate.sys.mjs for each MOZ_BUILD_APP,
+ *   by defining the method on the exported AppUiTestDelegate object.
+ *   All AppUiTestDelegate implementations must be kept in sync to have the
+ *   same interface!
+ *
+ * You should use the same method name across all of these files for ease of
+ * lookup and maintainability.
+ */
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  // Each app needs to implement this - see above comment.
+  AppUiTestDelegate: "resource://testing-common/AppUiTestDelegate.sys.mjs",
+});
+
+export class AppTestDelegateParent extends JSWindowActorParent {
+  constructor() {
+    super();
+    this._tabs = new Map();
+  }
+
+  get browser() {
+    return this.browsingContext.top.embedderElement;
+  }
+
+  get window() {
+    return this.browser.ownerGlobal;
+  }
+
+  async receiveMessage(message) {
+    const { extensionId, url, waitForLoad, tabId } = message.data;
+    switch (message.name) {
+      case "DOMContentLoaded":
+      case "load": {
+        return this.browser?.dispatchEvent(
+          new CustomEvent(`AppTestDelegate:${message.name}`, {
+            detail: {
+              browsingContext: this.browsingContext,
+              ...message.data,
+            },
+          })
+        );
+      }
+      case "clickPageAction":
+        return lazy.AppUiTestDelegate.clickPageAction(this.window, extensionId);
+      case "clickBrowserAction":
+        return lazy.AppUiTestDelegate.clickBrowserAction(
+          this.window,
+          extensionId
+        );
+      case "closePageAction":
+        return lazy.AppUiTestDelegate.closePageAction(this.window, extensionId);
+      case "closeBrowserAction":
+        return lazy.AppUiTestDelegate.closeBrowserAction(
+          this.window,
+          extensionId
+        );
+      case "awaitExtensionPanel":
+        // The desktop delegate returns a <browser>, but that cannot be sent
+        // over IPC, so just ignore it. The promise resolves when the panel and
+        // its content is fully loaded.
+        await lazy.AppUiTestDelegate.awaitExtensionPanel(
+          this.window,
+          extensionId
+        );
+        return null;
+      case "openNewForegroundTab": {
+        // We cannot send the tab object across process so let's store it with
+        // a unique ID here.
+        const uuid = Services.uuid.generateUUID().toString();
+        const tab = await lazy.AppUiTestDelegate.openNewForegroundTab(
+          this.window,
+          url,
+          waitForLoad
+        );
+        this._tabs.set(uuid, tab);
+        return uuid;
+      }
+      case "removeTab": {
+        const tab = this._tabs.get(tabId);
+        this._tabs.delete(tabId);
+        return lazy.AppUiTestDelegate.removeTab(tab);
+      }
+
+      default:
+        throw new Error(`Unknown Test API: ${message.name}.`);
+    }
+  }
+}
diff --git a/testing/specialpowers/content/ContentTaskUtils.sys.mjs b/testing/specialpowers/content/ContentTaskUtils.sys.mjs
new file mode 100644
index 0000000000..0d026d1e3b
--- /dev/null
+++ b/testing/specialpowers/content/ContentTaskUtils.sys.mjs
@@ -0,0 +1,249 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * This module implements a number of utility functions that can be loaded
+ * into content scope.
+ *
+ * All asynchronous helper methods should return promises, rather than being
+ * callback based.
+ */
+
+// Disable ownerGlobal use since that's not available on content-privileged elements.
+
+/* eslint-disable mozilla/use-ownerGlobal */
+
+import { setTimeout } from "resource://gre/modules/Timer.sys.mjs";
+
+export var ContentTaskUtils = {
+  /**
+   * Checks if a DOM element is hidden.
+   *
+   * @param {Element} element
+   *        The element which is to be checked.
+   *
+   * @return {boolean}
+   */
+  isHidden(element) {
+    let style = element.ownerDocument.defaultView.getComputedStyle(element);
+    if (style.display == "none") {
+      return true;
+    }
+    if (style.visibility != "visible") {
+      return true;
+    }
+
+    // Hiding a parent element will hide all its children
+    if (
+      element.parentNode != element.ownerDocument &&
+      element.parentNode.nodeType != Node.DOCUMENT_FRAGMENT_NODE
+    ) {
+      return ContentTaskUtils.isHidden(element.parentNode);
+    }
+
+    // Walk up the shadow DOM if we've reached the top of the shadow root
+    if (element.parentNode.host) {
+      return ContentTaskUtils.isHidden(element.parentNode.host);
+    }
+
+    return false;
+  },
+
+  /**
+   * Checks if a DOM element is visible.
+   *
+   * @param {Element} element
+   *        The element which is to be checked.
+   *
+   * @return {boolean}
+   */
+  isVisible(element) {
+    return !this.isHidden(element);
+  },
+
+  /**
+   * Will poll a condition function until it returns true.
+   *
+   * @param condition
+   *        A condition function that must return true or false. If the
+   *        condition ever throws, this is also treated as a false.
+   * @param msg
+   *        The message to use when the returned promise is rejected.
+   *        This message will be extended with additional information
+   *        about the number of tries or the thrown exception.
+   * @param interval
+   *        The time interval to poll the condition function. Defaults
+   *        to 100ms.
+   * @param maxTries
+   *        The number of times to poll before giving up and rejecting
+   *        if the condition has not yet returned true. Defaults to 50
+   *        (~5 seconds for 100ms intervals)
+   * @return Promise
+   *        Resolves when condition is true.
+   *        Rejects if timeout is exceeded or condition ever throws.
+   */
+  async waitForCondition(condition, msg, interval = 100, maxTries = 50) {
+    let startTime = Cu.now();
+    for (let tries = 0; tries < maxTries; ++tries) {
+      await new Promise(resolve => setTimeout(resolve, interval));
+
+      let conditionPassed = false;
+      try {
+        conditionPassed = await condition();
+      } catch (e) {
+        msg += ` - threw exception: ${e}`;
+        ChromeUtils.addProfilerMarker(
+          "ContentTaskUtils",
+          { startTime, category: "Test" },
+          `waitForCondition - ${msg}`
+        );
+        throw msg;
+      }
+      if (conditionPassed) {
+        ChromeUtils.addProfilerMarker(
+          "ContentTaskUtils",
+          { startTime, category: "Test" },
+          `waitForCondition succeeded after ${tries} retries - ${msg}`
+        );
+        return conditionPassed;
+      }
+    }
+
+    msg += ` - timed out after ${maxTries} tries.`;
+    ChromeUtils.addProfilerMarker(
+      "ContentTaskUtils",
+      { startTime, category: "Test" },
+      `waitForCondition - ${msg}`
+    );
+    throw msg;
+  },
+
+  /**
+   * Waits for an event to be fired on a specified element.
+   *
+   * Usage:
+   *    let promiseEvent = ContentTasKUtils.waitForEvent(element, "eventName");
+   *    // Do some processing here that will cause the event to be fired
+   *    // ...
+   *    // Now yield until the Promise is fulfilled
+   *    let receivedEvent = yield promiseEvent;
+   *
+   * @param {Element} subject
+   *        The element that should receive the event.
+   * @param {string} eventName
+   *        Name of the event to listen to.
+   * @param {bool} capture [optional]
+   *        True to use a capturing listener.
+   * @param {function} checkFn [optional]
+   *        Called with the Event object as argument, should return true if the
+   *        event is the expected one, or false if it should be ignored and
+   *        listening should continue. If not specified, the first event with
+   *        the specified name resolves the returned promise.
+   *
+   * @note Because this function is intended for testing, any error in checkFn
+   *       will cause the returned promise to be rejected instead of waiting for
+   *       the next event, since this is probably a bug in the test.
+   *
+   * @returns {Promise}
+   * @resolves The Event object.
+   */
+  waitForEvent(subject, eventName, capture, checkFn, wantsUntrusted = false) {
+    return new Promise((resolve, reject) => {
+      let startTime = Cu.now();
+      subject.addEventListener(
+        eventName,
+        function listener(event) {
+          try {
+            if (checkFn && !checkFn(event)) {
+              return;
+            }
+            subject.removeEventListener(eventName, listener, capture);
+            setTimeout(() => {
+              ChromeUtils.addProfilerMarker(
+                "ContentTaskUtils",
+                { category: "Test", startTime },
+                "waitForEvent - " + eventName
+              );
+              resolve(event);
+            }, 0);
+          } catch (ex) {
+            try {
+              subject.removeEventListener(eventName, listener, capture);
+            } catch (ex2) {
+              // Maybe the provided object does not support removeEventListener.
+            }
+            setTimeout(() => reject(ex), 0);
+          }
+        },
+        capture,
+        wantsUntrusted
+      );
+    });
+  },
+
+  /**
+   * Wait until DOM mutations cause the condition expressed in checkFn to pass.
+   * Intended as an easy-to-use alternative to waitForCondition.
+   *
+   * @param {Element} subject
+   *        The element on which to observe mutations.
+   * @param {Object} options
+   *        The options to pass to MutationObserver.observe();
+   * @param {function} checkFn [optional]
+   *        Function that returns true when it wants the promise to be resolved.
+   *        If not specified, the first mutation will resolve the promise.
+   *
+   * @returns {Promise<void>}
+   */
+  waitForMutationCondition(subject, options, checkFn) {
+    if (checkFn?.()) {
+      return Promise.resolve();
+    }
+    return new Promise(resolve => {
+      let obs = new subject.ownerGlobal.MutationObserver(function () {
+        if (checkFn && !checkFn()) {
+          return;
+        }
+        obs.disconnect();
+        resolve();
+      });
+      obs.observe(subject, options);
+    });
+  },
+
+  /**
+   * Gets an instance of the `EventUtils` helper module for usage in
+   * content tasks. See https://searchfox.org/mozilla-central/source/testing/mochitest/tests/SimpleTest/EventUtils.js
+   *
+   * @param content
+   *        The `content` global object from your content task.
+   *
+   * @returns an EventUtils instance.
+   */
+  getEventUtils(content) {
+    if (content._EventUtils) {
+      return content._EventUtils;
+    }
+
+    let EventUtils = (content._EventUtils = {});
+
+    EventUtils.window = {};
+    EventUtils.setTimeout = setTimeout;
+    EventUtils.parent = EventUtils.window;
+    /* eslint-disable camelcase */
+    EventUtils._EU_Ci = Ci;
+    EventUtils._EU_Cc = Cc;
+    /* eslint-enable camelcase */
+    // EventUtils' `sendChar` function relies on the navigator to synthetize events.
+    EventUtils.navigator = content.navigator;
+    EventUtils.KeyboardEvent = content.KeyboardEvent;
+
+    Services.scriptloader.loadSubScript(
+      "chrome://mochikit/content/tests/SimpleTest/EventUtils.js",
+      EventUtils
+    );
+
+    return EventUtils;
+  },
+};
diff --git a/testing/specialpowers/content/MockColorPicker.sys.mjs b/testing/specialpowers/content/MockColorPicker.sys.mjs
new file mode 100644
index 0000000000..1b4c4d3b3e
--- /dev/null
+++ b/testing/specialpowers/content/MockColorPicker.sys.mjs
@@ -0,0 +1,123 @@
+/* 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/. */
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  WrapPrivileged: "resource://testing-common/WrapPrivileged.sys.mjs",
+});
+
+const Cm = Components.manager;
+
+const CONTRACT_ID = "@mozilla.org/colorpicker;1";
+
+Cu.crashIfNotInAutomation();
+
+var registrar = Cm.QueryInterface(Ci.nsIComponentRegistrar);
+var oldClassID = "";
+var newClassID = Services.uuid.generateUUID();
+var newFactory = function (window) {
+  return {
+    createInstance(aIID) {
+      return new MockColorPickerInstance(window).QueryInterface(aIID);
+    },
+    QueryInterface: ChromeUtils.generateQI(["nsIFactory"]),
+  };
+};
+
+export var MockColorPicker = {
+  init(window) {
+    this.reset();
+    this.factory = newFactory(window);
+    if (!registrar.isCIDRegistered(newClassID)) {
+      try {
+        oldClassID = registrar.contractIDToCID(CONTRACT_ID);
+      } catch (ex) {
+        oldClassID = "";
+        dump(
+          "TEST-INFO | can't get colorpicker registered component, " +
+            "assuming there is none"
+        );
+      }
+      registrar.registerFactory(newClassID, "", CONTRACT_ID, this.factory);
+    }
+  },
+
+  reset() {
+    this.returnColor = "";
+    this.showCallback = null;
+    this.shown = false;
+    this.showing = false;
+  },
+
+  cleanup() {
+    var previousFactory = this.factory;
+    this.reset();
+    this.factory = null;
+
+    registrar.unregisterFactory(newClassID, previousFactory);
+    if (oldClassID != "") {
+      registrar.registerFactory(oldClassID, "", CONTRACT_ID, null);
+    }
+  },
+};
+
+function MockColorPickerInstance(window) {
+  this.window = window;
+  this.showCallback = null;
+  this.showCallbackWrapped = null;
+}
+MockColorPickerInstance.prototype = {
+  QueryInterface: ChromeUtils.generateQI(["nsIColorPicker"]),
+  init(aParent, aTitle, aInitialColor, aDefaultColors) {
+    this.parent = aParent;
+    this.initialColor = aInitialColor;
+    this.defaultColors = aDefaultColors;
+  },
+  initialColor: "",
+  parent: null,
+  open(aColorPickerShownCallback) {
+    MockColorPicker.showing = true;
+    MockColorPicker.shown = true;
+
+    this.window.setTimeout(() => {
+      let result = "";
+      try {
+        if (typeof MockColorPicker.showCallback == "function") {
+          if (MockColorPicker.showCallback != this.showCallback) {
+            this.showCallback = MockColorPicker.showCallback;
+            if (Cu.isXrayWrapper(this.window)) {
+              this.showCallbackWrapped = lazy.WrapPrivileged.wrapCallback(
+                MockColorPicker.showCallback,
+                this.window
+              );
+            } else {
+              this.showCallbackWrapped = this.showCallback;
+            }
+          }
+          var updateCb = function (color) {
+            result = color;
+            aColorPickerShownCallback.update(color);
+          };
+          let returnColor = this.showCallbackWrapped(this, updateCb);
+          if (typeof returnColor === "string") {
+            result = returnColor;
+          }
+        } else if (typeof MockColorPicker.returnColor === "string") {
+          result = MockColorPicker.returnColor;
+        }
+      } catch (ex) {
+        dump(
+          "TEST-UNEXPECTED-FAIL | Exception in MockColorPicker.sys.mjs open() " +
+            "method: " +
+            ex +
+            "\n"
+        );
+      }
+      if (aColorPickerShownCallback) {
+        aColorPickerShownCallback.done(result);
+      }
+    }, 0);
+  },
+};
diff --git a/testing/specialpowers/content/MockFilePicker.sys.mjs b/testing/specialpowers/content/MockFilePicker.sys.mjs
new file mode 100644
index 0000000000..ee2f11af75
--- /dev/null
+++ b/testing/specialpowers/content/MockFilePicker.sys.mjs
@@ -0,0 +1,318 @@
+/* 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/. */
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  FileUtils: "resource://gre/modules/FileUtils.sys.mjs",
+  WrapPrivileged: "resource://testing-common/WrapPrivileged.sys.mjs",
+});
+
+const Cm = Components.manager;
+
+const CONTRACT_ID = "@mozilla.org/filepicker;1";
+
+if (import.meta.url.includes("specialpowers")) {
+  Cu.crashIfNotInAutomation();
+}
+
+var registrar = Cm.QueryInterface(Ci.nsIComponentRegistrar);
+var oldClassID;
+var newClassID = Services.uuid.generateUUID();
+var newFactory = function (window) {
+  return {
+    createInstance(aIID) {
+      return new MockFilePickerInstance(window).QueryInterface(aIID);
+    },
+    QueryInterface: ChromeUtils.generateQI(["nsIFactory"]),
+  };
+};
+
+export var MockFilePicker = {
+  returnOK: Ci.nsIFilePicker.returnOK,
+  returnCancel: Ci.nsIFilePicker.returnCancel,
+  returnReplace: Ci.nsIFilePicker.returnReplace,
+
+  filterAll: Ci.nsIFilePicker.filterAll,
+  filterHTML: Ci.nsIFilePicker.filterHTML,
+  filterText: Ci.nsIFilePicker.filterText,
+  filterImages: Ci.nsIFilePicker.filterImages,
+  filterXML: Ci.nsIFilePicker.filterXML,
+  filterXUL: Ci.nsIFilePicker.filterXUL,
+  filterApps: Ci.nsIFilePicker.filterApps,
+  filterAllowURLs: Ci.nsIFilePicker.filterAllowURLs,
+  filterAudio: Ci.nsIFilePicker.filterAudio,
+  filterVideo: Ci.nsIFilePicker.filterVideo,
+
+  window: null,
+  pendingPromises: [],
+
+  init(window) {
+    this.window = window;
+
+    this.reset();
+    this.factory = newFactory(window);
+    if (!registrar.isCIDRegistered(newClassID)) {
+      oldClassID = registrar.contractIDToCID(CONTRACT_ID);
+      registrar.registerFactory(newClassID, "", CONTRACT_ID, this.factory);
+    }
+  },
+
+  reset() {
+    this.appendFilterCallback = null;
+    this.appendFiltersCallback = null;
+    this.displayDirectory = null;
+    this.displaySpecialDirectory = "";
+    this.filterIndex = 0;
+    this.mode = null;
+    this.returnData = [];
+    this.returnValue = null;
+    this.showCallback = null;
+    this.afterOpenCallback = null;
+    this.shown = false;
+    this.showing = false;
+  },
+
+  cleanup() {
+    var previousFactory = this.factory;
+    this.reset();
+    this.factory = null;
+    if (oldClassID) {
+      registrar.unregisterFactory(newClassID, previousFactory);
+      registrar.registerFactory(oldClassID, "", CONTRACT_ID, null);
+    }
+  },
+
+  internalFileData(obj) {
+    return {
+      nsIFile: "nsIFile" in obj ? obj.nsIFile : null,
+      domFile: "domFile" in obj ? obj.domFile : null,
+      domDirectory: "domDirectory" in obj ? obj.domDirectory : null,
+    };
+  },
+
+  useAnyFile() {
+    var file = lazy.FileUtils.getDir("TmpD", []);
+    file.append("testfile");
+    file.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, 0o644);
+    let promise = this.window.File.createFromNsIFile(file)
+      .then(
+        domFile => domFile,
+        () => null
+      )
+      // domFile can be null.
+      .then(domFile => {
+        this.returnData = [this.internalFileData({ nsIFile: file, domFile })];
+      })
+      .then(() => file);
+
+    this.pendingPromises = [promise];
+
+    // We return a promise in order to support some existing mochitests.
+    return promise;
+  },
+
+  useBlobFile() {
+    var blob = new this.window.Blob([]);
+    var file = new this.window.File([blob], "helloworld.txt", {
+      type: "plain/text",
+    });
+    this.returnData = [this.internalFileData({ domFile: file })];
+    this.pendingPromises = [];
+  },
+
+  useDirectory(aPath) {
+    var directory = new this.window.Directory(aPath);
+    var file = new lazy.FileUtils.File(aPath);
+    this.returnData = [
+      this.internalFileData({ domDirectory: directory, nsIFile: file }),
+    ];
+    this.pendingPromises = [];
+  },
+
+  setFiles(files) {
+    this.returnData = [];
+    this.pendingPromises = [];
+
+    for (let file of files) {
+      if (this.window.File.isInstance(file)) {
+        this.returnData.push(this.internalFileData({ domFile: file }));
+      } else {
+        let promise = this.window.File.createFromNsIFile(file, {
+          existenceCheck: false,
+        });
+
+        promise.then(domFile => {
+          this.returnData.push(
+            this.internalFileData({ nsIFile: file, domFile })
+          );
+        });
+        this.pendingPromises.push(promise);
+      }
+    }
+  },
+
+  getNsIFile() {
+    if (this.returnData.length >= 1) {
+      return this.returnData[0].nsIFile;
+    }
+    return null;
+  },
+};
+
+function MockFilePickerInstance(window) {
+  this.window = window;
+  this.showCallback = null;
+  this.showCallbackWrapped = null;
+}
+MockFilePickerInstance.prototype = {
+  QueryInterface: ChromeUtils.generateQI(["nsIFilePicker"]),
+  init(aParent, aTitle, aMode) {
+    this.mode = aMode;
+    this.filterIndex = MockFilePicker.filterIndex;
+    this.parent = aParent;
+  },
+  appendFilter(aTitle, aFilter) {
+    if (typeof MockFilePicker.appendFilterCallback == "function") {
+      MockFilePicker.appendFilterCallback(this, aTitle, aFilter);
+    }
+  },
+  appendFilters(aFilterMask) {
+    if (typeof MockFilePicker.appendFiltersCallback == "function") {
+      MockFilePicker.appendFiltersCallback(this, aFilterMask);
+    }
+  },
+  defaultString: "",
+  defaultExtension: "",
+  parent: null,
+  filterIndex: 0,
+  displayDirectory: null,
+  displaySpecialDirectory: "",
+  get file() {
+    if (MockFilePicker.returnData.length >= 1) {
+      return MockFilePicker.returnData[0].nsIFile;
+    }
+
+    return null;
+  },
+
+  // We don't support directories here.
+  get domFileOrDirectory() {
+    if (MockFilePicker.returnData.length < 1) {
+      return null;
+    }
+
+    if (MockFilePicker.returnData[0].domFile) {
+      return MockFilePicker.returnData[0].domFile;
+    }
+
+    if (MockFilePicker.returnData[0].domDirectory) {
+      return MockFilePicker.returnData[0].domDirectory;
+    }
+
+    return null;
+  },
+  get fileURL() {
+    if (
+      MockFilePicker.returnData.length >= 1 &&
+      MockFilePicker.returnData[0].nsIFile
+    ) {
+      return Services.io.newFileURI(MockFilePicker.returnData[0].nsIFile);
+    }
+
+    return null;
+  },
+  *getFiles(asDOM) {
+    for (let d of MockFilePicker.returnData) {
+      if (asDOM) {
+        yield d.domFile || d.domDirectory;
+      } else if (d.nsIFile) {
+        yield d.nsIFile;
+      } else {
+        throw Components.Exception("", Cr.NS_ERROR_FAILURE);
+      }
+    }
+  },
+  get files() {
+    return this.getFiles(false);
+  },
+  get domFileOrDirectoryEnumerator() {
+    return this.getFiles(true);
+  },
+  open(aFilePickerShownCallback) {
+    MockFilePicker.showing = true;
+    Services.tm.dispatchToMainThread(() => {
+      // Maybe all the pending promises are already resolved, but we want to be sure.
+      Promise.all(MockFilePicker.pendingPromises)
+        .then(
+          () => {
+            return Ci.nsIFilePicker.returnOK;
+          },
+          () => {
+            return Ci.nsIFilePicker.returnCancel;
+          }
+        )
+        .then(result => {
+          // Nothing else has to be done.
+          MockFilePicker.pendingPromises = [];
+
+          if (result == Ci.nsIFilePicker.returnCancel) {
+            return result;
+          }
+
+          MockFilePicker.displayDirectory = this.displayDirectory;
+          MockFilePicker.displaySpecialDirectory = this.displaySpecialDirectory;
+          MockFilePicker.shown = true;
+          if (typeof MockFilePicker.showCallback == "function") {
+            if (MockFilePicker.showCallback != this.showCallback) {
+              this.showCallback = MockFilePicker.showCallback;
+              if (Cu.isXrayWrapper(this.window)) {
+                this.showCallbackWrapped = lazy.WrapPrivileged.wrapCallback(
+                  MockFilePicker.showCallback,
+                  this.window
+                );
+              } else {
+                this.showCallbackWrapped = this.showCallback;
+              }
+            }
+            try {
+              var returnValue = this.showCallbackWrapped(this);
+              if (typeof returnValue != "undefined") {
+                return returnValue;
+              }
+            } catch (ex) {
+              return Ci.nsIFilePicker.returnCancel;
+            }
+          }
+
+          return MockFilePicker.returnValue;
+        })
+        .then(result => {
+          // Some additional result file can be set by the callback. Let's
+          // resolve the pending promises again.
+          return Promise.all(MockFilePicker.pendingPromises).then(
+            () => {
+              return result;
+            },
+            () => {
+              return Ci.nsIFilePicker.returnCancel;
+            }
+          );
+        })
+        .then(result => {
+          MockFilePicker.pendingPromises = [];
+
+          if (aFilePickerShownCallback) {
+            aFilePickerShownCallback.done(result);
+          }
+
+          if (typeof MockFilePicker.afterOpenCallback == "function") {
+            Services.tm.dispatchToMainThread(() => {
+              MockFilePicker.afterOpenCallback(this);
+            });
+          }
+        });
+    });
+  },
+};
diff --git a/testing/specialpowers/content/MockPermissionPrompt.sys.mjs b/testing/specialpowers/content/MockPermissionPrompt.sys.mjs
new file mode 100644
index 0000000000..615c786f2c
--- /dev/null
+++ b/testing/specialpowers/content/MockPermissionPrompt.sys.mjs
@@ -0,0 +1,75 @@
+/* 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/. */
+
+const Cm = Components.manager;
+
+const CONTRACT_ID = "@mozilla.org/content-permission/prompt;1";
+
+var registrar = Cm.QueryInterface(Ci.nsIComponentRegistrar);
+var oldClassID, oldFactory;
+var newClassID = Services.uuid.generateUUID();
+var newFactory = {
+  createInstance(aIID) {
+    return new MockPermissionPromptInstance().QueryInterface(aIID);
+  },
+  QueryInterface: ChromeUtils.generateQI(["nsIFactory"]),
+};
+
+export var MockPermissionPrompt = {
+  init() {
+    this.reset();
+    if (!registrar.isCIDRegistered(newClassID)) {
+      try {
+        oldClassID = registrar.contractIDToCID(CONTRACT_ID);
+        oldFactory = Cm.getClassObject(Cc[CONTRACT_ID], Ci.nsIFactory);
+      } catch (ex) {
+        oldClassID = "";
+        oldFactory = null;
+        dump(
+          "TEST-INFO | can't get permission prompt registered component, " +
+            "assuming there is none"
+        );
+      }
+      if (oldFactory) {
+        registrar.unregisterFactory(oldClassID, oldFactory);
+      }
+      registrar.registerFactory(newClassID, "", CONTRACT_ID, newFactory);
+    }
+  },
+
+  reset() {},
+
+  cleanup() {
+    this.reset();
+    if (oldFactory) {
+      registrar.unregisterFactory(newClassID, newFactory);
+      registrar.registerFactory(oldClassID, "", CONTRACT_ID, oldFactory);
+    }
+  },
+};
+
+function MockPermissionPromptInstance() {}
+MockPermissionPromptInstance.prototype = {
+  QueryInterface: ChromeUtils.generateQI(["nsIContentPermissionPrompt"]),
+
+  promptResult: Ci.nsIPermissionManager.UNKNOWN_ACTION,
+
+  prompt(request) {
+    let perms = request.types.QueryInterface(Ci.nsIArray);
+    for (let idx = 0; idx < perms.length; idx++) {
+      let perm = perms.queryElementAt(idx, Ci.nsIContentPermissionType);
+      if (
+        Services.perms.testExactPermissionFromPrincipal(
+          request.principal,
+          perm.type
+        ) != Ci.nsIPermissionManager.ALLOW_ACTION
+      ) {
+        request.cancel();
+        return;
+      }
+    }
+
+    request.allow();
+  },
+};
diff --git a/testing/specialpowers/content/SpecialPowersChild.sys.mjs b/testing/specialpowers/content/SpecialPowersChild.sys.mjs
new file mode 100644
index 0000000000..20afe12d39
--- /dev/null
+++ b/testing/specialpowers/content/SpecialPowersChild.sys.mjs
@@ -0,0 +1,2333 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+/* This code is loaded in every child process that is started by mochitest.
+ */
+
+import { ExtensionUtils } from "resource://gre/modules/ExtensionUtils.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  ContentTaskUtils: "resource://testing-common/ContentTaskUtils.sys.mjs",
+  MockColorPicker: "resource://testing-common/MockColorPicker.sys.mjs",
+  MockFilePicker: "resource://testing-common/MockFilePicker.sys.mjs",
+  MockPermissionPrompt:
+    "resource://testing-common/MockPermissionPrompt.sys.mjs",
+  NetUtil: "resource://gre/modules/NetUtil.sys.mjs",
+  PerTestCoverageUtils:
+    "resource://testing-common/PerTestCoverageUtils.sys.mjs",
+  PrivateBrowsingUtils: "resource://gre/modules/PrivateBrowsingUtils.sys.mjs",
+  SpecialPowersSandbox:
+    "resource://testing-common/SpecialPowersSandbox.sys.mjs",
+  WrapPrivileged: "resource://testing-common/WrapPrivileged.sys.mjs",
+});
+import { AppConstants } from "resource://gre/modules/AppConstants.sys.mjs";
+
+Cu.crashIfNotInAutomation();
+
+function bindDOMWindowUtils(aWindow) {
+  return aWindow && lazy.WrapPrivileged.wrap(aWindow.windowUtils, aWindow);
+}
+
+function defineSpecialPowers(sp) {
+  let window = sp.contentWindow;
+  window.SpecialPowers = sp;
+  if (window === window.wrappedJSObject) {
+    return;
+  }
+  // We can't use a generic |defineLazyGetter| because it does not
+  // allow customizing the re-definition behavior.
+  Object.defineProperty(window.wrappedJSObject, "SpecialPowers", {
+    get() {
+      let value = lazy.WrapPrivileged.wrap(sp, window);
+      // If we bind |window.wrappedJSObject| when defining the getter
+      // and use it here, it might become a dead wrapper.
+      // We have to retrieve |wrappedJSObject| again.
+      Object.defineProperty(window.wrappedJSObject, "SpecialPowers", {
+        configurable: true,
+        enumerable: true,
+        value,
+        writable: true,
+      });
+      return value;
+    },
+    configurable: true,
+    enumerable: true,
+  });
+}
+
+// SPConsoleListener reflects nsIConsoleMessage objects into JS in a
+// tidy, XPCOM-hiding way.  Messages that are nsIScriptError objects
+// have their properties exposed in detail.  It also auto-unregisters
+// itself when it receives a "sentinel" message.
+function SPConsoleListener(callback, contentWindow) {
+  this.callback = callback;
+  this.contentWindow = contentWindow;
+}
+
+SPConsoleListener.prototype = {
+  // Overload the observe method for both nsIConsoleListener and nsIObserver.
+  // The topic will be null for nsIConsoleListener.
+  observe(msg, topic) {
+    let m = {
+      message: msg.message,
+      errorMessage: null,
+      cssSelectors: null,
+      sourceName: null,
+      sourceLine: null,
+      lineNumber: null,
+      columnNumber: null,
+      category: null,
+      windowID: null,
+      isScriptError: false,
+      isConsoleEvent: false,
+      isWarning: false,
+    };
+    if (msg instanceof Ci.nsIScriptError) {
+      m.errorMessage = msg.errorMessage;
+      m.cssSelectors = msg.cssSelectors;
+      m.sourceName = msg.sourceName;
+      m.sourceLine = msg.sourceLine;
+      m.lineNumber = msg.lineNumber;
+      m.columnNumber = msg.columnNumber;
+      m.category = msg.category;
+      m.windowID = msg.outerWindowID;
+      m.innerWindowID = msg.innerWindowID;
+      m.isScriptError = true;
+      m.isWarning = (msg.flags & Ci.nsIScriptError.warningFlag) === 1;
+    }
+
+    Object.freeze(m);
+
+    // Run in a separate runnable since console listeners aren't
+    // supposed to touch content and this one might.
+    Services.tm.dispatchToMainThread(() => {
+      this.callback.call(undefined, Cu.cloneInto(m, this.contentWindow));
+    });
+
+    if (!m.isScriptError && !m.isConsoleEvent && m.message === "SENTINEL") {
+      Services.console.unregisterListener(this);
+    }
+  },
+
+  QueryInterface: ChromeUtils.generateQI(["nsIConsoleListener", "nsIObserver"]),
+};
+
+export class SpecialPowersChild extends JSWindowActorChild {
+  constructor() {
+    super();
+
+    this._windowID = null;
+
+    this._encounteredCrashDumpFiles = [];
+    this._unexpectedCrashDumpFiles = {};
+    this._crashDumpDir = null;
+    this._serviceWorkerRegistered = false;
+    this._serviceWorkerCleanUpRequests = new Map();
+    Object.defineProperty(this, "Components", {
+      configurable: true,
+      enumerable: true,
+      value: Components,
+    });
+    this._createFilesOnError = null;
+    this._createFilesOnSuccess = null;
+
+    this._messageListeners = new ExtensionUtils.DefaultMap(() => new Set());
+
+    this._consoleListeners = [];
+    this._spawnTaskImports = {};
+    this._encounteredCrashDumpFiles = [];
+    this._unexpectedCrashDumpFiles = {};
+    this._crashDumpDir = null;
+    this._mfl = null;
+    this._asyncObservers = new WeakMap();
+    this._xpcomabi = null;
+    this._os = null;
+    this._pu = null;
+
+    this._nextExtensionID = 0;
+    this._extensionListeners = null;
+
+    lazy.WrapPrivileged.disableAutoWrap(
+      this.unwrap,
+      this.isWrapper,
+      this.wrapCallback,
+      this.wrapCallbackObject,
+      this.setWrapped,
+      this.nondeterministicGetWeakMapKeys,
+      this.snapshotWindowWithOptions,
+      this.snapshotWindow,
+      this.snapshotRect,
+      this.getDOMRequestService
+    );
+  }
+
+  observe(aSubject, aTopic, aData) {
+    // Ignore the "{chrome/content}-document-global-created" event. It
+    // is only observed to force creation of the actor.
+  }
+
+  actorCreated() {
+    this.attachToWindow();
+  }
+
+  attachToWindow() {
+    let window = this.contentWindow;
+    // We should not invoke the getter.
+    if (!("SpecialPowers" in window.wrappedJSObject)) {
+      this._windowID = window.windowGlobalChild.innerWindowId;
+
+      defineSpecialPowers(this);
+    }
+  }
+
+  get window() {
+    return this.contentWindow;
+  }
+
+  // Hack around devtools sometimes trying to JSON stringify us.
+  toJSON() {
+    return {};
+  }
+
+  toString() {
+    return "[SpecialPowers]";
+  }
+  sanityCheck() {
+    return "foo";
+  }
+
+  _addMessageListener(msgname, listener) {
+    this._messageListeners.get(msgname).add(listener);
+  }
+
+  _removeMessageListener(msgname, listener) {
+    this._messageListeners.get(msgname).delete(listener);
+  }
+
+  receiveMessage(message) {
+    if (this._messageListeners.has(message.name)) {
+      for (let listener of this._messageListeners.get(message.name)) {
+        try {
+          if (typeof listener === "function") {
+            listener(message);
+          } else {
+            listener.receiveMessage(message);
+          }
+        } catch (e) {
+          console.error(e);
+        }
+      }
+    }
+
+    switch (message.name) {
+      case "SPProcessCrashService":
+        if (message.json.type == "crash-observed") {
+          for (let e of message.json.dumpIDs) {
+            this._encounteredCrashDumpFiles.push(e.id + "." + e.extension);
+          }
+        }
+        break;
+
+      case "SPServiceWorkerRegistered":
+        this._serviceWorkerRegistered = message.data.registered;
+        break;
+
+      case "SpecialPowers.FilesCreated":
+        var createdHandler = this._createFilesOnSuccess;
+        this._createFilesOnSuccess = null;
+        this._createFilesOnError = null;
+        if (createdHandler) {
+          createdHandler(Cu.cloneInto(message.data, this.contentWindow));
+        }
+        break;
+
+      case "SpecialPowers.FilesError":
+        var errorHandler = this._createFilesOnError;
+        this._createFilesOnSuccess = null;
+        this._createFilesOnError = null;
+        if (errorHandler) {
+          errorHandler(message.data);
+        }
+        break;
+
+      case "Spawn":
+        let { task, args, caller, taskId, imports } = message.data;
+        return this._spawnTask(task, args, caller, taskId, imports);
+
+      case "EnsureFocus":
+        // Ensure that the focus is in this child document. Returns a browsing
+        // context of a child frame if a subframe should be focused or undefined
+        // otherwise.
+
+        // If a subframe node is focused, then the focus will actually
+        // be within that subframe's document. If blurSubframe is true,
+        // then blur the subframe so that this parent document is focused
+        // instead. If blurSubframe is false, then return the browsing
+        // context for that subframe. The parent process will then call back
+        // into this same code but in the process for that subframe.
+        let focusedNode = this.document.activeElement;
+        let subframeFocused =
+          ChromeUtils.getClassName(focusedNode) == "HTMLIFrameElement" ||
+          ChromeUtils.getClassName(focusedNode) == "HTMLFrameElement" ||
+          ChromeUtils.getClassName(focusedNode) == "XULFrameElement";
+        if (subframeFocused) {
+          if (message.data.blurSubframe) {
+            Services.focus.clearFocus(this.contentWindow);
+          } else {
+            if (!this.document.hasFocus()) {
+              this.contentWindow.focus();
+            }
+            return Promise.resolve(focusedNode.browsingContext);
+          }
+        }
+
+        // A subframe is not focused, so if this document is
+        // not focused, focus it and wait for the focus event.
+        if (!this.document.hasFocus()) {
+          return new Promise(resolve => {
+            this.document.addEventListener(
+              "focus",
+              () => {
+                resolve();
+              },
+              {
+                capture: true,
+                once: true,
+              }
+            );
+            this.contentWindow.focus();
+          });
+        }
+        break;
+
+      case "Assert":
+        {
+          if ("info" in message.data) {
+            (this.xpcshellScope || this.SimpleTest).info(message.data.info);
+            break;
+          }
+
+          // An assertion has been done in a mochitest chrome script
+          let { name, passed, stack, diag, expectFail } = message.data;
+
+          let { SimpleTest } = this;
+          if (SimpleTest) {
+            let expected = expectFail ? "fail" : "pass";
+            SimpleTest.record(passed, name, diag, stack, expected);
+          } else if (this.xpcshellScope) {
+            this.xpcshellScope.do_report_result(passed, name, stack);
+          } else {
+            // Well, this is unexpected.
+            dump(name + "\n");
+          }
+        }
+        break;
+    }
+    return undefined;
+  }
+
+  registerProcessCrashObservers() {
+    this.sendAsyncMessage("SPProcessCrashService", { op: "register-observer" });
+  }
+
+  unregisterProcessCrashObservers() {
+    this.sendAsyncMessage("SPProcessCrashService", {
+      op: "unregister-observer",
+    });
+  }
+
+  /*
+   * Privileged object wrapping API
+   *
+   * Usage:
+   *   var wrapper = SpecialPowers.wrap(obj);
+   *   wrapper.privilegedMethod(); wrapper.privilegedProperty;
+   *   obj === SpecialPowers.unwrap(wrapper);
+   *
+   * These functions provide transparent access to privileged objects using
+   * various pieces of deep SpiderMagic. Conceptually, a wrapper is just an
+   * object containing a reference to the underlying object, where all method
+   * calls and property accesses are transparently performed with the System
+   * Principal. Moreover, objects obtained from the wrapper (including properties
+   * and method return values) are wrapped automatically. Thus, after a single
+   * call to SpecialPowers.wrap(), the wrapper layer is transitively maintained.
+   *
+   * Known Issues:
+   *
+   *  - The wrapping function does not preserve identity, so
+   *    SpecialPowers.wrap(foo) !== SpecialPowers.wrap(foo). See bug 718543.
+   *
+   *  - The wrapper cannot see expando properties on unprivileged DOM objects.
+   *    That is to say, the wrapper uses Xray delegation.
+   *
+   *  - The wrapper sometimes guesses certain ES5 attributes for returned
+   *    properties. This is explained in a comment in the wrapper code above,
+   *    and shouldn't be a problem.
+   */
+  wrap(obj) {
+    return obj;
+  }
+  unwrap(obj) {
+    return lazy.WrapPrivileged.unwrap(obj);
+  }
+  isWrapper(val) {
+    return lazy.WrapPrivileged.isWrapper(val);
+  }
+
+  unwrapIfWrapped(obj) {
+    return lazy.WrapPrivileged.isWrapper(obj)
+      ? lazy.WrapPrivileged.unwrap(obj)
+      : obj;
+  }
+
+  /*
+   * Wrap objects on a specified global.
+   */
+  wrapFor(obj, win) {
+    return lazy.WrapPrivileged.wrap(obj, win);
+  }
+
+  /*
+   * When content needs to pass a callback or a callback object to an API
+   * accessed over SpecialPowers, that API may sometimes receive arguments for
+   * whom it is forbidden to create a wrapper in content scopes. As such, we
+   * need a layer to wrap the values in SpecialPowers wrappers before they ever
+   * reach content.
+   */
+  wrapCallback(func) {
+    return lazy.WrapPrivileged.wrapCallback(func, this.contentWindow);
+  }
+  wrapCallbackObject(obj) {
+    return lazy.WrapPrivileged.wrapCallbackObject(obj, this.contentWindow);
+  }
+
+  /*
+   * Used for assigning a property to a SpecialPowers wrapper, without unwrapping
+   * the value that is assigned.
+   */
+  setWrapped(obj, prop, val) {
+    if (!lazy.WrapPrivileged.isWrapper(obj)) {
+      throw new Error(
+        "You only need to use this for SpecialPowers wrapped objects"
+      );
+    }
+
+    obj = lazy.WrapPrivileged.unwrap(obj);
+    return Reflect.set(obj, prop, val);
+  }
+
+  /*
+   * Create blank privileged objects to use as out-params for privileged functions.
+   */
+  createBlankObject() {
+    return {};
+  }
+
+  /*
+   * Because SpecialPowers wrappers don't preserve identity, comparing with ==
+   * can be hazardous. Sometimes we can just unwrap to compare, but sometimes
+   * wrapping the underlying object into a content scope is forbidden. This
+   * function strips any wrappers if they exist and compare the underlying
+   * values.
+   */
+  compare(a, b) {
+    return lazy.WrapPrivileged.unwrap(a) === lazy.WrapPrivileged.unwrap(b);
+  }
+
+  get MockFilePicker() {
+    return lazy.MockFilePicker;
+  }
+
+  get MockColorPicker() {
+    return lazy.MockColorPicker;
+  }
+
+  get MockPermissionPrompt() {
+    return lazy.MockPermissionPrompt;
+  }
+
+  quit() {
+    this.sendAsyncMessage("SpecialPowers.Quit", {});
+  }
+
+  // fileRequests is an array of file requests. Each file request is an object.
+  // A request must have a field |name|, which gives the base of the name of the
+  // file to be created in the profile directory. If the request has a |data| field
+  // then that data will be written to the file.
+  createFiles(fileRequests, onCreation, onError) {
+    return this.sendQuery("SpecialPowers.CreateFiles", fileRequests).then(
+      files => onCreation(Cu.cloneInto(files, this.contentWindow)),
+      onError
+    );
+  }
+
+  // Remove the files that were created using |SpecialPowers.createFiles()|.
+  // This will be automatically called by |SimpleTest.finish()|.
+  removeFiles() {
+    this.sendAsyncMessage("SpecialPowers.RemoveFiles", {});
+  }
+
+  executeAfterFlushingMessageQueue(aCallback) {
+    return this.sendQuery("Ping").then(aCallback);
+  }
+
+  async registeredServiceWorkers() {
+    // Please see the comment in SpecialPowersObserver.jsm above
+    // this._serviceWorkerListener's assignment for what this returns.
+    if (this._serviceWorkerRegistered) {
+      // This test registered at least one service worker. Send a synchronous
+      // call to the parent to make sure that it called unregister on all of its
+      // service workers.
+      let { workers } = await this.sendQuery("SPCheckServiceWorkers");
+      return workers;
+    }
+
+    return [];
+  }
+
+  /*
+   * Load a privileged script that runs same-process. This is different from
+   * |loadChromeScript|, which will run in the parent process in e10s mode.
+   */
+  loadPrivilegedScript(aFunction) {
+    var str = "(" + aFunction.toString() + ")();";
+    let gGlobalObject = Cu.getGlobalForObject(this);
+    let sb = Cu.Sandbox(gGlobalObject);
+    var window = this.contentWindow;
+    var mc = new window.MessageChannel();
+    sb.port = mc.port1;
+    let blob = new Blob([str], { type: "application/javascript" });
+    let blobUrl = URL.createObjectURL(blob);
+    Services.scriptloader.loadSubScript(blobUrl, sb);
+
+    return mc.port2;
+  }
+
+  _readUrlAsString(aUrl) {
+    // Fetch script content as we can't use scriptloader's loadSubScript
+    // to evaluate http:// urls...
+    var scriptableStream = Cc[
+      "@mozilla.org/scriptableinputstream;1"
+    ].getService(Ci.nsIScriptableInputStream);
+
+    var channel = lazy.NetUtil.newChannel({
+      uri: aUrl,
+      loadUsingSystemPrincipal: true,
+    });
+    var input = channel.open();
+    scriptableStream.init(input);
+
+    var str;
+    var buffer = [];
+
+    while ((str = scriptableStream.read(4096))) {
+      buffer.push(str);
+    }
+
+    var output = buffer.join("");
+
+    scriptableStream.close();
+    input.close();
+
+    var status;
+    if (channel instanceof Ci.nsIHttpChannel) {
+      status = channel.responseStatus;
+    }
+
+    if (status == 404) {
+      throw new Error(
+        `Error while executing chrome script '${aUrl}':\n` +
+          "The script doesn't exist. Ensure you have registered it in " +
+          "'support-files' in your mochitest.ini."
+      );
+    }
+
+    return output;
+  }
+
+  loadChromeScript(urlOrFunction, sandboxOptions) {
+    // Create a unique id for this chrome script
+    let id = Services.uuid.generateUUID().toString();
+
+    // Tells chrome code to evaluate this chrome script
+    let scriptArgs = { id, sandboxOptions };
+    if (typeof urlOrFunction == "function") {
+      scriptArgs.function = {
+        body: "(" + urlOrFunction.toString() + ")();",
+        name: urlOrFunction.name,
+      };
+    } else {
+      // Note: We need to do this in the child since, even though
+      // `_readUrlAsString` pretends to be synchronous, its channel
+      // winds up spinning the event loop when loading HTTP URLs. That
+      // leads to unexpected out-of-order operations if the child sends
+      // a message immediately after loading the script.
+      scriptArgs.function = {
+        body: this._readUrlAsString(urlOrFunction),
+      };
+      scriptArgs.url = urlOrFunction;
+    }
+    this.sendAsyncMessage("SPLoadChromeScript", scriptArgs);
+
+    // Returns a MessageManager like API in order to be
+    // able to communicate with this chrome script
+    let listeners = [];
+    let chromeScript = {
+      addMessageListener: (name, listener) => {
+        listeners.push({ name, listener });
+      },
+
+      promiseOneMessage: name =>
+        new Promise(resolve => {
+          chromeScript.addMessageListener(name, function listener(message) {
+            chromeScript.removeMessageListener(name, listener);
+            resolve(message);
+          });
+        }),
+
+      removeMessageListener: (name, listener) => {
+        listeners = listeners.filter(
+          o => o.name != name || o.listener != listener
+        );
+      },
+
+      sendAsyncMessage: (name, message) => {
+        this.sendAsyncMessage("SPChromeScriptMessage", { id, name, message });
+      },
+
+      sendQuery: (name, message) => {
+        return this.sendQuery("SPChromeScriptMessage", { id, name, message });
+      },
+
+      destroy: () => {
+        listeners = [];
+        this._removeMessageListener("SPChromeScriptMessage", chromeScript);
+      },
+
+      receiveMessage: aMessage => {
+        let messageId = aMessage.json.id;
+        let name = aMessage.json.name;
+        let message = aMessage.json.message;
+        if (this.contentWindow) {
+          message = new StructuredCloneHolder(
+            `SpecialPowers/receiveMessage/${name}`,
+            null,
+            message
+          ).deserialize(this.contentWindow);
+        }
+        // Ignore message from other chrome script
+        if (messageId != id) {
+          return null;
+        }
+
+        let result;
+        if (aMessage.name == "SPChromeScriptMessage") {
+          for (let listener of listeners.filter(o => o.name == name)) {
+            result = listener.listener(message);
+          }
+        }
+        return result;
+      },
+    };
+    this._addMessageListener("SPChromeScriptMessage", chromeScript);
+
+    return chromeScript;
+  }
+
+  get Services() {
+    return Services;
+  }
+
+  /*
+   * Convenient shortcuts to the standard Components abbreviations.
+   */
+  get Cc() {
+    return Cc;
+  }
+  get Ci() {
+    return Ci;
+  }
+  get Cu() {
+    return Cu;
+  }
+  get Cr() {
+    return Cr;
+  }
+
+  get ChromeUtils() {
+    return ChromeUtils;
+  }
+
+  get isHeadless() {
+    return Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo).isHeadless;
+  }
+
+  get addProfilerMarker() {
+    return ChromeUtils.addProfilerMarker;
+  }
+
+  get DOMWindowUtils() {
+    return this.contentWindow.windowUtils;
+  }
+
+  getDOMWindowUtils(aWindow) {
+    if (aWindow == this.contentWindow) {
+      return aWindow.windowUtils;
+    }
+
+    return bindDOMWindowUtils(Cu.unwaiveXrays(aWindow));
+  }
+
+  async toggleMuteState(aMuted, aWindow) {
+    let actor = aWindow
+      ? aWindow.windowGlobalChild.getActor("SpecialPowers")
+      : this;
+    return actor.sendQuery("SPToggleMuteAudio", { mute: aMuted });
+  }
+
+  /*
+   * A method to get a DOMParser that can't parse XUL.
+   */
+  getNoXULDOMParser() {
+    // If we create it with a system subject principal (so it gets a
+    // nullprincipal), it won't be able to parse XUL by default.
+    return new DOMParser();
+  }
+
+  get InspectorUtils() {
+    return InspectorUtils;
+  }
+
+  get PromiseDebugging() {
+    return PromiseDebugging;
+  }
+
+  async waitForCrashes(aExpectingProcessCrash) {
+    if (!aExpectingProcessCrash) {
+      return;
+    }
+
+    var crashIds = this._encounteredCrashDumpFiles
+      .filter(filename => {
+        return filename.length === 40 && filename.endsWith(".dmp");
+      })
+      .map(id => {
+        return id.slice(0, -4); // Strip the .dmp extension to get the ID
+      });
+
+    await this.sendQuery("SPProcessCrashManagerWait", {
+      crashIds,
+    });
+  }
+
+  async removeExpectedCrashDumpFiles(aExpectingProcessCrash) {
+    var success = true;
+    if (aExpectingProcessCrash) {
+      var message = {
+        op: "delete-crash-dump-files",
+        filenames: this._encounteredCrashDumpFiles,
+      };
+      if (!(await this.sendQuery("SPProcessCrashService", message))) {
+        success = false;
+      }
+    }
+    this._encounteredCrashDumpFiles.length = 0;
+    return success;
+  }
+
+  async findUnexpectedCrashDumpFiles() {
+    var self = this;
+    var message = {
+      op: "find-crash-dump-files",
+      crashDumpFilesToIgnore: this._unexpectedCrashDumpFiles,
+    };
+    var crashDumpFiles = await this.sendQuery("SPProcessCrashService", message);
+    crashDumpFiles.forEach(function (aFilename) {
+      self._unexpectedCrashDumpFiles[aFilename] = true;
+    });
+    return crashDumpFiles;
+  }
+
+  removePendingCrashDumpFiles() {
+    var message = {
+      op: "delete-pending-crash-dump-files",
+    };
+    return this.sendQuery("SPProcessCrashService", message);
+  }
+
+  _setTimeout(callback, delay = 0) {
+    // for mochitest-browser
+    if (typeof this.chromeWindow != "undefined") {
+      this.chromeWindow.setTimeout(callback, delay);
+    }
+    // for mochitest-plain
+    else {
+      this.contentWindow.setTimeout(callback, delay);
+    }
+  }
+
+  promiseTimeout(delay) {
+    return new Promise(resolve => {
+      this._setTimeout(resolve, delay);
+    });
+  }
+
+  _delayCallbackTwice(callback) {
+    let delayedCallback = () => {
+      let delayAgain = aCallback => {
+        // Using this._setTimeout doesn't work here
+        // It causes failures in mochtests that use
+        // multiple pushPrefEnv calls
+        // For chrome/browser-chrome mochitests
+        this._setTimeout(aCallback);
+      };
+      delayAgain(delayAgain.bind(this, callback));
+    };
+    return delayedCallback;
+  }
+
+  /* apply permissions to the system and when the test case is finished (SimpleTest.finish())
+     we will revert the permission back to the original.
+
+     inPermissions is an array of objects where each object has a type, action, context, ex:
+     [{'type': 'SystemXHR', 'allow': 1, 'context': document},
+      {'type': 'SystemXHR', 'allow': Ci.nsIPermissionManager.PROMPT_ACTION, 'context': document}]
+
+     Allow can be a boolean value of true/false or ALLOW_ACTION/DENY_ACTION/PROMPT_ACTION/UNKNOWN_ACTION
+  */
+  async pushPermissions(inPermissions, callback) {
+    let permissions = [];
+    for (let perm of inPermissions) {
+      let principal = this._getPrincipalFromArg(perm.context);
+      permissions.push({
+        ...perm,
+        context: null,
+        principal,
+      });
+    }
+
+    await this.sendQuery("PushPermissions", permissions).then(callback);
+    await this.promiseTimeout(0);
+  }
+
+  async popPermissions(callback = null) {
+    await this.sendQuery("PopPermissions").then(callback);
+    await this.promiseTimeout(0);
+  }
+
+  async flushPermissions(callback = null) {
+    await this.sendQuery("FlushPermissions").then(callback);
+    await this.promiseTimeout(0);
+  }
+
+  /*
+   * This function should be used when specialpowers is in content process but
+   * it want to get the notification from chrome space.
+   *
+   * This function will call Services.obs.addObserver in SpecialPowersObserver
+   * (that is in chrome process) and forward the data received to SpecialPowers
+   * via messageManager.
+   * You can use this._addMessageListener("specialpowers-YOUR_TOPIC") to fire
+   * the callback.
+   *
+   * To get the expected data, you should modify
+   * SpecialPowersObserver.prototype._registerObservers.observe. Or the message
+   * you received from messageManager will only contain 'aData' from Service.obs.
+   */
+  registerObservers(topic) {
+    var msg = {
+      op: "add",
+      observerTopic: topic,
+    };
+    return this.sendQuery("SPObserverService", msg);
+  }
+
+  async pushPrefEnv(inPrefs, callback = null) {
+    let { requiresRefresh } = await this.sendQuery("PushPrefEnv", inPrefs);
+    if (callback) {
+      await callback();
+    }
+    if (requiresRefresh) {
+      await this._promiseEarlyRefresh();
+    }
+  }
+
+  async popPrefEnv(callback = null) {
+    let { popped, requiresRefresh } = await this.sendQuery("PopPrefEnv");
+    if (callback) {
+      await callback(popped);
+    }
+    if (requiresRefresh) {
+      await this._promiseEarlyRefresh();
+    }
+  }
+
+  async flushPrefEnv(callback = null) {
+    let { requiresRefresh } = await this.sendQuery("FlushPrefEnv");
+    if (callback) {
+      await callback();
+    }
+    if (requiresRefresh) {
+      await this._promiseEarlyRefresh();
+    }
+  }
+
+  /*
+    Collect a snapshot of all preferences in Firefox (i.e. about:prefs).
+    From this, store the results within specialpowers for later reference.
+  */
+  async getBaselinePrefs(callback = null) {
+    await this.sendQuery("getBaselinePrefs");
+    if (callback) {
+      await callback();
+    }
+  }
+
+  /*
+    This uses the stored prefs from getBaselinePrefs, collects a new snapshot
+    of preferences, then compares the new vs the baseline.  If there are differences
+    they are recorded and returned as an array of preferences, in addition
+    all the changed preferences are reset to the value found in the baseline.
+
+    ignorePrefs: array of strings which are preferences.  If they end in *,
+                 we do a partial match
+  */
+  async comparePrefsToBaseline(ignorePrefs, callback = null) {
+    let retVal = await this.sendQuery("comparePrefsToBaseline", ignorePrefs);
+    if (callback) {
+      callback(retVal);
+    }
+    return retVal;
+  }
+
+  _promiseEarlyRefresh() {
+    return new Promise(r => {
+      // for mochitest-browser
+      if (typeof this.chromeWindow != "undefined") {
+        this.chromeWindow.requestAnimationFrame(r);
+      }
+      // for mochitest-plain
+      else {
+        this.contentWindow.requestAnimationFrame(r);
+      }
+    });
+  }
+
+  _addObserverProxy(notification) {
+    if (notification in this._proxiedObservers) {
+      this._addMessageListener(
+        notification,
+        this._proxiedObservers[notification]
+      );
+    }
+  }
+  _removeObserverProxy(notification) {
+    if (notification in this._proxiedObservers) {
+      this._removeMessageListener(
+        notification,
+        this._proxiedObservers[notification]
+      );
+    }
+  }
+
+  addObserver(obs, notification, weak) {
+    // Make sure the parent side exists, or we won't get any notifications.
+    this.sendAsyncMessage("Wakeup");
+
+    this._addObserverProxy(notification);
+    obs = Cu.waiveXrays(obs);
+    if (
+      typeof obs == "object" &&
+      obs.observe.name != "SpecialPowersCallbackWrapper"
+    ) {
+      obs.observe = lazy.WrapPrivileged.wrapCallback(
+        Cu.unwaiveXrays(obs.observe),
+        this.contentWindow
+      );
+    }
+    Services.obs.addObserver(obs, notification, weak);
+  }
+  removeObserver(obs, notification) {
+    this._removeObserverProxy(notification);
+    Services.obs.removeObserver(Cu.waiveXrays(obs), notification);
+  }
+  notifyObservers(subject, topic, data) {
+    Services.obs.notifyObservers(subject, topic, data);
+  }
+
+  /**
+   * An async observer is useful if you're listening for a
+   * notification that normally is only used by C++ code or chrome
+   * code (so it runs in the SystemGroup), but we need to know about
+   * it for a test (which runs as web content). If we used
+   * addObserver, we would assert when trying to enter web content
+   * from a runnabled labeled by the SystemGroup. An async observer
+   * avoids this problem.
+   */
+  addAsyncObserver(obs, notification, weak) {
+    obs = Cu.waiveXrays(obs);
+    if (
+      typeof obs == "object" &&
+      obs.observe.name != "SpecialPowersCallbackWrapper"
+    ) {
+      obs.observe = lazy.WrapPrivileged.wrapCallback(
+        Cu.unwaiveXrays(obs.observe),
+        this.contentWindow
+      );
+    }
+    let asyncObs = (...args) => {
+      Services.tm.dispatchToMainThread(() => {
+        if (typeof obs == "function") {
+          obs(...args);
+        } else {
+          obs.observe.call(undefined, ...args);
+        }
+      });
+    };
+    this._asyncObservers.set(obs, asyncObs);
+    Services.obs.addObserver(asyncObs, notification, weak);
+  }
+  removeAsyncObserver(obs, notification) {
+    let asyncObs = this._asyncObservers.get(Cu.waiveXrays(obs));
+    Services.obs.removeObserver(asyncObs, notification);
+  }
+
+  can_QI(obj) {
+    return obj.QueryInterface !== undefined;
+  }
+  do_QueryInterface(obj, iface) {
+    return obj.QueryInterface(Ci[iface]);
+  }
+
+  call_Instanceof(obj1, obj2) {
+    obj1 = lazy.WrapPrivileged.unwrap(obj1);
+    obj2 = lazy.WrapPrivileged.unwrap(obj2);
+    return obj1 instanceof obj2;
+  }
+
+  // Returns a privileged getter from an object. GetOwnPropertyDescriptor does
+  // not work here because xray wrappers don't properly implement it.
+  //
+  // This terribleness is used by dom/base/test/test_object.html because
+  // <object> and <embed> tags will spawn plugins if their prototype is touched,
+  // so we need to get and cache the getter of |hasRunningPlugin| if we want to
+  // call it without paradoxically spawning the plugin.
+  do_lookupGetter(obj, name) {
+    return Object.prototype.__lookupGetter__.call(obj, name);
+  }
+
+  // Mimic the get*Pref API
+  getBoolPref(...args) {
+    return Services.prefs.getBoolPref(...args);
+  }
+  getIntPref(...args) {
+    return Services.prefs.getIntPref(...args);
+  }
+  getCharPref(...args) {
+    return Services.prefs.getCharPref(...args);
+  }
+  getComplexValue(prefName, iid) {
+    return Services.prefs.getComplexValue(prefName, iid);
+  }
+  getStringPref(...args) {
+    return Services.prefs.getStringPref(...args);
+  }
+
+  getParentBoolPref(prefName, defaultValue) {
+    return this._getParentPref(prefName, "BOOL", { defaultValue });
+  }
+  getParentIntPref(prefName, defaultValue) {
+    return this._getParentPref(prefName, "INT", { defaultValue });
+  }
+  getParentCharPref(prefName, defaultValue) {
+    return this._getParentPref(prefName, "CHAR", { defaultValue });
+  }
+  getParentStringPref(prefName, defaultValue) {
+    return this._getParentPref(prefName, "STRING", { defaultValue });
+  }
+
+  // Mimic the set*Pref API
+  setBoolPref(prefName, value) {
+    return this._setPref(prefName, "BOOL", value);
+  }
+  setIntPref(prefName, value) {
+    return this._setPref(prefName, "INT", value);
+  }
+  setCharPref(prefName, value) {
+    return this._setPref(prefName, "CHAR", value);
+  }
+  setComplexValue(prefName, iid, value) {
+    return this._setPref(prefName, "COMPLEX", value, iid);
+  }
+  setStringPref(prefName, value) {
+    return this._setPref(prefName, "STRING", value);
+  }
+
+  // Mimic the clearUserPref API
+  clearUserPref(prefName) {
+    let msg = {
+      op: "clear",
+      prefName,
+      prefType: "",
+    };
+    return this.sendQuery("SPPrefService", msg);
+  }
+
+  // Private pref functions to communicate to chrome
+  async _getParentPref(prefName, prefType, { defaultValue, iid }) {
+    let msg = {
+      op: "get",
+      prefName,
+      prefType,
+      iid, // Only used with complex prefs
+      defaultValue, // Optional default value
+    };
+    let val = await this.sendQuery("SPPrefService", msg);
+    if (val == null) {
+      throw new Error(`Error getting pref '${prefName}'`);
+    }
+    return val;
+  }
+  _getPref(prefName, prefType, { defaultValue }) {
+    switch (prefType) {
+      case "BOOL":
+        return Services.prefs.getBoolPref(prefName);
+      case "INT":
+        return Services.prefs.getIntPref(prefName);
+      case "CHAR":
+        return Services.prefs.getCharPref(prefName);
+      case "STRING":
+        return Services.prefs.getStringPref(prefName);
+    }
+    return undefined;
+  }
+  _setPref(prefName, prefType, prefValue, iid) {
+    let msg = {
+      op: "set",
+      prefName,
+      prefType,
+      iid, // Only used with complex prefs
+      prefValue,
+    };
+    return this.sendQuery("SPPrefService", msg);
+  }
+
+  _getMUDV(window) {
+    return window.docShell.docViewer;
+  }
+  // XXX: these APIs really ought to be removed, they're not e10s-safe.
+  // (also they're pretty Firefox-specific)
+  _getTopChromeWindow(window) {
+    return window.browsingContext.topChromeWindow;
+  }
+  _getAutoCompletePopup(window) {
+    return this._getTopChromeWindow(window).document.getElementById(
+      "PopupAutoComplete"
+    );
+  }
+  addAutoCompletePopupEventListener(window, eventname, listener) {
+    this._getAutoCompletePopup(window).addEventListener(eventname, listener);
+  }
+  removeAutoCompletePopupEventListener(window, eventname, listener) {
+    this._getAutoCompletePopup(window).removeEventListener(eventname, listener);
+  }
+  getFormFillController(window) {
+    return Cc["@mozilla.org/satchel/form-fill-controller;1"].getService(
+      Ci.nsIFormFillController
+    );
+  }
+  attachFormFillControllerTo(window) {
+    this.getFormFillController().attachPopupElementToDocument(
+      window.document,
+      this._getAutoCompletePopup(window)
+    );
+  }
+  detachFormFillControllerFrom(window) {
+    this.getFormFillController().detachFromDocument(window.document);
+  }
+  isBackButtonEnabled(window) {
+    return !this._getTopChromeWindow(window)
+      .document.getElementById("Browser:Back")
+      .hasAttribute("disabled");
+  }
+  // XXX end of problematic APIs
+
+  addChromeEventListener(type, listener, capture, allowUntrusted) {
+    this.docShell.chromeEventHandler.addEventListener(
+      type,
+      listener,
+      capture,
+      allowUntrusted
+    );
+  }
+  removeChromeEventListener(type, listener, capture) {
+    this.docShell.chromeEventHandler.removeEventListener(
+      type,
+      listener,
+      capture
+    );
+  }
+
+  async generateMediaControlKeyTestEvent(event) {
+    await this.sendQuery("SPGenerateMediaControlKeyTestEvent", { event });
+  }
+
+  // Note: each call to registerConsoleListener MUST be paired with a
+  // call to postConsoleSentinel; when the callback receives the
+  // sentinel it will unregister itself (_after_ calling the
+  // callback).  SimpleTest.expectConsoleMessages does this for you.
+  // If you register more than one console listener, a call to
+  // postConsoleSentinel will zap all of them.
+  registerConsoleListener(callback) {
+    let listener = new SPConsoleListener(callback, this.contentWindow);
+    Services.console.registerListener(listener);
+  }
+  postConsoleSentinel() {
+    Services.console.logStringMessage("SENTINEL");
+  }
+  resetConsole() {
+    Services.console.reset();
+  }
+
+  getFullZoom(window) {
+    return BrowsingContext.getFromWindow(window).fullZoom;
+  }
+
+  getDeviceFullZoom(window) {
+    return this._getMUDV(window).deviceFullZoomForTest;
+  }
+  setFullZoom(window, zoom) {
+    BrowsingContext.getFromWindow(window).fullZoom = zoom;
+  }
+  getTextZoom(window) {
+    return BrowsingContext.getFromWindow(window).textZoom;
+  }
+  setTextZoom(window, zoom) {
+    BrowsingContext.getFromWindow(window).textZoom = zoom;
+  }
+
+  emulateMedium(window, mediaType) {
+    BrowsingContext.getFromWindow(window).top.mediumOverride = mediaType;
+  }
+
+  stopEmulatingMedium(window) {
+    BrowsingContext.getFromWindow(window).top.mediumOverride = "";
+  }
+
+  // Takes a snapshot of the given window and returns a <canvas>
+  // containing the image. When the window is same-process, the canvas
+  // is returned synchronously. When it is out-of-process (or when a
+  // BrowsingContext or FrameLoaderOwner is passed instead of a Window),
+  // a promise which resolves to such a canvas is returned instead.
+  snapshotWindowWithOptions(content, rect, bgcolor, options) {
+    function getImageData(rect, bgcolor, options) {
+      let el = content.document.createElementNS(
+        "http://www.w3.org/1999/xhtml",
+        "canvas"
+      );
+      if (rect === undefined) {
+        rect = {
+          top: content.scrollY,
+          left: content.scrollX,
+          width: content.innerWidth,
+          height: content.innerHeight,
+        };
+      }
+      if (bgcolor === undefined) {
+        bgcolor = "rgb(255,255,255)";
+      }
+      if (options === undefined) {
+        options = {};
+      }
+
+      el.width = rect.width;
+      el.height = rect.height;
+      let ctx = el.getContext("2d");
+
+      let flags = 0;
+      for (let option in options) {
+        flags |= options[option] && ctx[option];
+      }
+
+      ctx.drawWindow(
+        content,
+        rect.left,
+        rect.top,
+        rect.width,
+        rect.height,
+        bgcolor,
+        flags
+      );
+
+      return ctx.getImageData(0, 0, el.width, el.height);
+    }
+
+    let toCanvas = imageData => {
+      let el = this.document.createElementNS(
+        "http://www.w3.org/1999/xhtml",
+        "canvas"
+      );
+      el.width = imageData.width;
+      el.height = imageData.height;
+
+      if (ImageData.isInstance(imageData)) {
+        let ctx = el.getContext("2d");
+        ctx.putImageData(imageData, 0, 0);
+      }
+
+      return el;
+    };
+
+    if (!Cu.isRemoteProxy(content) && Window.isInstance(content)) {
+      // Hack around tests that try to snapshot 0 width or height
+      // elements.
+      if (rect && !(rect.width && rect.height)) {
+        return toCanvas(rect);
+      }
+
+      // This is an in-process window. Snapshot it synchronously.
+      return toCanvas(getImageData(rect, bgcolor, options));
+    }
+
+    // This is a remote window or frame. Snapshot it asynchronously and
+    // return a promise for the result. Alas, consumers expect us to
+    // return a <canvas> element rather than an ImageData object, so we
+    // need to convert the result from the remote snapshot to a local
+    // canvas.
+    let promise = this.spawn(
+      content,
+      [rect, bgcolor, options],
+      getImageData
+    ).then(toCanvas);
+    if (Cu.isXrayWrapper(this.contentWindow)) {
+      return new this.contentWindow.Promise((resolve, reject) => {
+        promise.then(resolve, reject);
+      });
+    }
+    return promise;
+  }
+
+  snapshotWindow(win, withCaret, rect, bgcolor) {
+    return this.snapshotWindowWithOptions(win, rect, bgcolor, {
+      DRAWWINDOW_DRAW_CARET: withCaret,
+    });
+  }
+
+  snapshotRect(win, rect, bgcolor) {
+    return this.snapshotWindowWithOptions(win, rect, bgcolor);
+  }
+
+  gc() {
+    this.contentWindow.windowUtils.garbageCollect();
+  }
+
+  forceGC() {
+    Cu.forceGC();
+  }
+
+  forceShrinkingGC() {
+    Cu.forceShrinkingGC();
+  }
+
+  forceCC() {
+    Cu.forceCC();
+  }
+
+  finishCC() {
+    Cu.finishCC();
+  }
+
+  ccSlice(budget) {
+    Cu.ccSlice(budget);
+  }
+
+  // Due to various dependencies between JS objects and C++ objects, an ordinary
+  // forceGC doesn't necessarily clear all unused objects, thus the GC and CC
+  // needs to run several times and when no other JS is running.
+  // The current number of iterations has been determined according to massive
+  // cross platform testing.
+  exactGC(callback) {
+    let count = 0;
+
+    function genGCCallback(cb) {
+      return function () {
+        Cu.forceCC();
+        if (++count < 3) {
+          Cu.schedulePreciseGC(genGCCallback(cb));
+        } else if (cb) {
+          cb();
+        }
+      };
+    }
+
+    Cu.schedulePreciseGC(genGCCallback(callback));
+  }
+
+  nondeterministicGetWeakMapKeys(m) {
+    let keys = ChromeUtils.nondeterministicGetWeakMapKeys(m);
+    if (!keys) {
+      return undefined;
+    }
+    return this.contentWindow.Array.from(keys);
+  }
+
+  getMemoryReports() {
+    try {
+      Cc["@mozilla.org/memory-reporter-manager;1"]
+        .getService(Ci.nsIMemoryReporterManager)
+        .getReports(
+          () => {},
+          null,
+          () => {},
+          null,
+          false
+        );
+    } catch (e) {}
+  }
+
+  setGCZeal(zeal) {
+    Cu.setGCZeal(zeal);
+  }
+
+  isMainProcess() {
+    try {
+      return (
+        Services.appinfo.processType == Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT
+      );
+    } catch (e) {}
+    return true;
+  }
+
+  get XPCOMABI() {
+    if (this._xpcomabi != null) {
+      return this._xpcomabi;
+    }
+
+    var xulRuntime = Services.appinfo.QueryInterface(Ci.nsIXULRuntime);
+
+    this._xpcomabi = xulRuntime.XPCOMABI;
+    return this._xpcomabi;
+  }
+
+  // The optional aWin parameter allows the caller to specify a given window in
+  // whose scope the runnable should be dispatched. If aFun throws, the
+  // exception will be reported to aWin.
+  executeSoon(aFun, aWin) {
+    // Create the runnable in the scope of aWin to avoid running into COWs.
+    var runnable = {};
+    if (aWin) {
+      runnable = Cu.createObjectIn(aWin);
+    }
+    runnable.run = aFun;
+    Cu.dispatch(runnable, aWin);
+  }
+
+  get OS() {
+    if (this._os != null) {
+      return this._os;
+    }
+
+    this._os = Services.appinfo.OS;
+    return this._os;
+  }
+
+  get useRemoteSubframes() {
+    return this.docShell.nsILoadContext.useRemoteSubframes;
+  }
+
+  ISOLATION_STRATEGY = {
+    IsolateNothing: 0,
+    IsolateEverything: 1,
+    IsolateHighValue: 2,
+  };
+
+  effectiveIsolationStrategy() {
+    // If remote subframes are disabled, we always use the IsolateNothing strategy.
+    if (!this.useRemoteSubframes) {
+      return this.ISOLATION_STRATEGY.IsolateNothing;
+    }
+    return this.getIntPref("fission.webContentIsolationStrategy");
+  }
+
+  addSystemEventListener(target, type, listener, useCapture) {
+    Services.els.addSystemEventListener(target, type, listener, useCapture);
+  }
+  removeSystemEventListener(target, type, listener, useCapture) {
+    Services.els.removeSystemEventListener(target, type, listener, useCapture);
+  }
+
+  // helper method to check if the event is consumed by either default group's
+  // event listener or system group's event listener.
+  defaultPreventedInAnyGroup(event) {
+    // FYI: Event.defaultPrevented returns false in content context if the
+    //      event is consumed only by system group's event listeners.
+    return event.defaultPrevented;
+  }
+
+  getDOMRequestService() {
+    var serv = Services.DOMRequest;
+    var res = {};
+    var props = [
+      "createRequest",
+      "createCursor",
+      "fireError",
+      "fireSuccess",
+      "fireDone",
+      "fireDetailedError",
+    ];
+    for (var i in props) {
+      let prop = props[i];
+      res[prop] = function () {
+        return serv[prop].apply(serv, arguments);
+      };
+    }
+    return Cu.cloneInto(res, this.contentWindow, { cloneFunctions: true });
+  }
+
+  addCategoryEntry(category, entry, value, persists, replace) {
+    Services.catMan.addCategoryEntry(category, entry, value, persists, replace);
+  }
+
+  deleteCategoryEntry(category, entry, persists) {
+    Services.catMan.deleteCategoryEntry(category, entry, persists);
+  }
+  openDialog(win, args) {
+    return win.openDialog.apply(win, args);
+  }
+  // This is a blocking call which creates and spins a native event loop
+  spinEventLoop(win) {
+    // simply do a sync XHR back to our windows location.
+    var syncXHR = new win.XMLHttpRequest();
+    syncXHR.open("GET", win.location, false);
+    syncXHR.send();
+  }
+
+  // :jdm gets credit for this.  ex: getPrivilegedProps(window, 'location.href');
+  getPrivilegedProps(obj, props) {
+    var parts = props.split(".");
+    for (var i = 0; i < parts.length; i++) {
+      var p = parts[i];
+      if (obj[p] != undefined) {
+        obj = obj[p];
+      } else {
+        return null;
+      }
+    }
+    return obj;
+  }
+
+  _browsingContextForTarget(target) {
+    if (BrowsingContext.isInstance(target)) {
+      return target;
+    }
+    if (Element.isInstance(target)) {
+      return target.browsingContext;
+    }
+
+    return BrowsingContext.getFromWindow(target);
+  }
+
+  getBrowsingContextID(target) {
+    return this._browsingContextForTarget(target).id;
+  }
+
+  *getGroupTopLevelWindows(target) {
+    let { group } = this._browsingContextForTarget(target);
+    for (let bc of group.getToplevels()) {
+      yield bc.window;
+    }
+  }
+
+  /**
+   * Runs a task in the context of the given frame, and returns a
+   * promise which resolves to the return value of that task.
+   *
+   * The given frame may be in-process or out-of-process. Either way,
+   * the task will run asynchronously, in a sandbox with access to the
+   * frame's content window via its `content` global. Any arguments
+   * passed will be copied via structured clone, as will its return
+   * value.
+   *
+   * The sandbox also has access to an Assert object, as provided by
+   * Assert.sys.mjs. Any assertion methods called before the task resolves
+   * will be relayed back to the test environment of the caller.
+   *
+   * @param {BrowsingContext or FrameLoaderOwner or WindowProxy} target
+   *        The target in which to run the task. This may be any element
+   *        which implements the FrameLoaderOwner interface (including
+   *        HTML <iframe> elements and XUL <browser> elements) or a
+   *        WindowProxy (either in-process or remote).
+   * @param {Array<any>} args
+   *        An array of arguments to pass to the task. All arguments
+   *        must be structured clone compatible, and will be cloned
+   *        before being passed to the task.
+   * @param {function} task
+   *        The function to run in the context of the target. The
+   *        function will be stringified and re-evaluated in the context
+   *        of the target's content window. It may return any structured
+   *        clone compatible value, or a Promise which resolves to the
+   *        same, which will be returned to the caller.
+   *
+   * @returns {Promise<any>}
+   *        A promise which resolves to the return value of the task, or
+   *        which rejects if the task raises an exception. As this is
+   *        being written, the rejection value will always be undefined
+   *        in the cases where the task throws an error, though that may
+   *        change in the future.
+   */
+  spawn(target, args, task) {
+    let browsingContext = this._browsingContextForTarget(target);
+
+    return this.sendQuery("Spawn", {
+      browsingContext,
+      args,
+      task: String(task),
+      caller: Cu.getFunctionSourceLocation(task),
+      hasHarness:
+        typeof this.SimpleTest === "object" ||
+        typeof this.xpcshellScope === "object",
+      imports: this._spawnTaskImports,
+    });
+  }
+
+  /**
+   * Like `spawn`, but spawns a chrome task in the parent process,
+   * instead. The task additionally has access to `windowGlobalParent`
+   * and `browsingContext` globals corresponding to the window from
+   * which the task was spawned.
+   */
+  spawnChrome(args, task) {
+    return this.sendQuery("SpawnChrome", {
+      args,
+      task: String(task),
+      caller: Cu.getFunctionSourceLocation(task),
+      imports: this._spawnTaskImports,
+    });
+  }
+
+  snapshotContext(target, rect, background, resetScrollPosition = false) {
+    let browsingContext = this._browsingContextForTarget(target);
+
+    return this.sendQuery("Snapshot", {
+      browsingContext,
+      rect,
+      background,
+      resetScrollPosition,
+    }).then(imageData => {
+      return this.contentWindow.createImageBitmap(imageData);
+    });
+  }
+
+  getSecurityState(target) {
+    let browsingContext = this._browsingContextForTarget(target);
+
+    return this.sendQuery("SecurityState", {
+      browsingContext,
+    });
+  }
+
+  _spawnTask(task, args, caller, taskId, imports) {
+    let sb = new lazy.SpecialPowersSandbox(
+      null,
+      data => {
+        this.sendAsyncMessage("ProxiedAssert", { taskId, data });
+      },
+      { imports }
+    );
+
+    sb.sandbox.SpecialPowers = this;
+    sb.sandbox.ContentTaskUtils = lazy.ContentTaskUtils;
+    for (let [global, prop] of Object.entries({
+      content: "contentWindow",
+      docShell: "docShell",
+    })) {
+      Object.defineProperty(sb.sandbox, global, {
+        get: () => {
+          return this[prop];
+        },
+        enumerable: true,
+      });
+    }
+
+    return sb.execute(task, args, caller);
+  }
+
+  /**
+   * Automatically imports the given symbol from the given sys.mjs for any
+   * task spawned by this SpecialPowers instance.
+   */
+  addTaskImport(symbol, url) {
+    this._spawnTaskImports[symbol] = url;
+  }
+
+  get SimpleTest() {
+    return this._SimpleTest || this.contentWindow.wrappedJSObject.SimpleTest;
+  }
+  set SimpleTest(val) {
+    this._SimpleTest = val;
+  }
+
+  get xpcshellScope() {
+    return this._xpcshellScope;
+  }
+  set xpcshellScope(val) {
+    this._xpcshellScope = val;
+  }
+
+  async evictAllDocumentViewers() {
+    if (Services.appinfo.sessionHistoryInParent) {
+      await this.sendQuery("EvictAllDocumentViewers");
+    } else {
+      this.browsingContext.top.childSessionHistory.legacySHistory.evictAllDocumentViewers();
+    }
+  }
+
+  /**
+   * Sets this actor as the default assertion result handler for tasks
+   * which originate in a window without a test harness.
+   */
+  setAsDefaultAssertHandler() {
+    this.sendAsyncMessage("SetAsDefaultAssertHandler");
+  }
+
+  getFocusedElementForWindow(targetWindow, aDeep) {
+    var outParam = {};
+    Services.focus.getFocusedElementForWindow(targetWindow, aDeep, outParam);
+    return outParam.value;
+  }
+
+  get focusManager() {
+    return Services.focus;
+  }
+
+  activeWindow() {
+    return Services.focus.activeWindow;
+  }
+
+  focusedWindow() {
+    return Services.focus.focusedWindow;
+  }
+
+  clearFocus(aWindow) {
+    Services.focus.clearFocus(aWindow);
+  }
+
+  focus(aWindow) {
+    // This is called inside TestRunner._makeIframe without aWindow, because of assertions in oop mochitests
+    // With aWindow, it is called in SimpleTest.waitForFocus to allow popup window opener focus switching
+    if (aWindow) {
+      aWindow.focus();
+    }
+
+    try {
+      let actor = aWindow
+        ? aWindow.windowGlobalChild.getActor("SpecialPowers")
+        : this;
+      actor.sendAsyncMessage("SpecialPowers.Focus", {});
+    } catch (e) {
+      console.error(e);
+    }
+  }
+
+  ensureFocus(aBrowsingContext, aBlurSubframe) {
+    return this.sendQuery("EnsureFocus", {
+      browsingContext: aBrowsingContext,
+      blurSubframe: aBlurSubframe,
+    });
+  }
+
+  getClipboardData(flavor, whichClipboard) {
+    if (whichClipboard === undefined) {
+      whichClipboard = Services.clipboard.kGlobalClipboard;
+    }
+
+    var xferable = Cc["@mozilla.org/widget/transferable;1"].createInstance(
+      Ci.nsITransferable
+    );
+    xferable.init(this.docShell);
+    xferable.addDataFlavor(flavor);
+    Services.clipboard.getData(
+      xferable,
+      whichClipboard,
+      this.browsingContext.currentWindowContext
+    );
+    var data = {};
+    try {
+      xferable.getTransferData(flavor, data);
+    } catch (e) {}
+    data = data.value || null;
+    if (data == null) {
+      return "";
+    }
+
+    return data.QueryInterface(Ci.nsISupportsString).data;
+  }
+
+  clipboardCopyString(str) {
+    Cc["@mozilla.org/widget/clipboardhelper;1"]
+      .getService(Ci.nsIClipboardHelper)
+      .copyString(str);
+  }
+
+  supportsSelectionClipboard() {
+    return Services.clipboard.isClipboardTypeSupported(
+      Services.clipboard.kSelectionClipboard
+    );
+  }
+
+  swapFactoryRegistration(cid, contractID, newFactory) {
+    newFactory = Cu.waiveXrays(newFactory);
+
+    var componentRegistrar = Components.manager.QueryInterface(
+      Ci.nsIComponentRegistrar
+    );
+
+    var currentCID = componentRegistrar.contractIDToCID(contractID);
+    var currentFactory = Components.manager.getClassObject(
+      Cc[contractID],
+      Ci.nsIFactory
+    );
+    if (cid) {
+      componentRegistrar.unregisterFactory(currentCID, currentFactory);
+    } else {
+      cid = Services.uuid.generateUUID();
+    }
+
+    // Restore the original factory.
+    componentRegistrar.registerFactory(cid, "", contractID, newFactory);
+    return { originalCID: currentCID };
+  }
+
+  _getElement(aWindow, id) {
+    return typeof id == "string" ? aWindow.document.getElementById(id) : id;
+  }
+
+  dispatchEvent(aWindow, target, event) {
+    var el = this._getElement(aWindow, target);
+    return el.dispatchEvent(event);
+  }
+
+  get isDebugBuild() {
+    return Cc["@mozilla.org/xpcom/debug;1"].getService(Ci.nsIDebug2)
+      .isDebugBuild;
+  }
+  assertionCount() {
+    var debugsvc = Cc["@mozilla.org/xpcom/debug;1"].getService(Ci.nsIDebug2);
+    return debugsvc.assertionCount;
+  }
+
+  /**
+   * @param arg one of the following:
+   *            - A URI string.
+   *            - A document node.
+   *            - A dictionary including a URL (`url`) and origin attributes (`attr`).
+   */
+  _getPrincipalFromArg(arg) {
+    arg = lazy.WrapPrivileged.unwrap(Cu.unwaiveXrays(arg));
+
+    if (arg.nodePrincipal) {
+      // It's a document.
+      return arg.nodePrincipal;
+    }
+
+    let secMan = Services.scriptSecurityManager;
+    if (typeof arg == "string") {
+      // It's a URL.
+      let uri = Services.io.newURI(arg);
+      return secMan.createContentPrincipal(uri, {});
+    }
+
+    let uri = Services.io.newURI(arg.url);
+    let attrs = arg.originAttributes || {};
+    return secMan.createContentPrincipal(uri, attrs);
+  }
+
+  async addPermission(type, allow, arg, expireType, expireTime) {
+    let principal = this._getPrincipalFromArg(arg);
+    if (principal.isSystemPrincipal) {
+      return; // nothing to do
+    }
+
+    let permission = allow;
+    if (typeof permission === "boolean") {
+      permission =
+        Ci.nsIPermissionManager[allow ? "ALLOW_ACTION" : "DENY_ACTION"];
+    }
+
+    var msg = {
+      op: "add",
+      type,
+      permission,
+      principal,
+      expireType: typeof expireType === "number" ? expireType : 0,
+      expireTime: typeof expireTime === "number" ? expireTime : 0,
+    };
+
+    await this.sendQuery("SPPermissionManager", msg);
+  }
+
+  /**
+   * @param type see nsIPermissionsManager::testPermissionFromPrincipal.
+   * @param arg one of the following:
+   *            - A URI string.
+   *            - A document node.
+   *            - A dictionary including a URL (`url`) and origin attributes (`attr`).
+   */
+  async removePermission(type, arg) {
+    let principal = this._getPrincipalFromArg(arg);
+    if (principal.isSystemPrincipal) {
+      return; // nothing to do
+    }
+
+    var msg = {
+      op: "remove",
+      type,
+      principal,
+    };
+
+    await this.sendQuery("SPPermissionManager", msg);
+  }
+
+  async hasPermission(type, arg) {
+    let principal = this._getPrincipalFromArg(arg);
+    if (principal.isSystemPrincipal) {
+      return true; // system principals have all permissions
+    }
+
+    var msg = {
+      op: "has",
+      type,
+      principal,
+    };
+
+    return this.sendQuery("SPPermissionManager", msg);
+  }
+
+  async testPermission(type, value, arg) {
+    let principal = this._getPrincipalFromArg(arg);
+    if (principal.isSystemPrincipal) {
+      return true; // system principals have all permissions
+    }
+
+    var msg = {
+      op: "test",
+      type,
+      value,
+      principal,
+    };
+    return this.sendQuery("SPPermissionManager", msg);
+  }
+
+  isContentWindowPrivate(win) {
+    return lazy.PrivateBrowsingUtils.isContentWindowPrivate(win);
+  }
+
+  async notifyObserversInParentProcess(subject, topic, data) {
+    if (subject) {
+      throw new Error("Can't send subject to another process!");
+    }
+    if (this.isMainProcess()) {
+      this.notifyObservers(subject, topic, data);
+      return;
+    }
+    var msg = {
+      op: "notify",
+      observerTopic: topic,
+      observerData: data,
+    };
+    await this.sendQuery("SPObserverService", msg);
+  }
+
+  removeAllServiceWorkerData() {
+    return this.sendQuery("SPRemoveAllServiceWorkers", {});
+  }
+
+  removeServiceWorkerDataForExampleDomain() {
+    return this.sendQuery("SPRemoveServiceWorkerDataForExampleDomain", {});
+  }
+
+  cleanUpSTSData(origin, flags) {
+    return this.sendQuery("SPCleanUpSTSData", { origin });
+  }
+
+  async requestDumpCoverageCounters(cb) {
+    // We want to avoid a roundtrip between child and parent.
+    if (!lazy.PerTestCoverageUtils.enabled) {
+      return;
+    }
+
+    await this.sendQuery("SPRequestDumpCoverageCounters", {});
+  }
+
+  async requestResetCoverageCounters(cb) {
+    // We want to avoid a roundtrip between child and parent.
+    if (!lazy.PerTestCoverageUtils.enabled) {
+      return;
+    }
+    await this.sendQuery("SPRequestResetCoverageCounters", {});
+  }
+
+  loadExtension(ext, handler) {
+    if (this._extensionListeners == null) {
+      this._extensionListeners = new Set();
+
+      this._addMessageListener("SPExtensionMessage", msg => {
+        for (let listener of this._extensionListeners) {
+          try {
+            listener(msg);
+          } catch (e) {
+            console.error(e);
+          }
+        }
+      });
+    }
+
+    // Note, this is not the addon is as used by the AddonManager etc,
+    // this is just an identifier used for specialpowers messaging
+    // between this content process and the chrome process.
+    let id = this._nextExtensionID++;
+
+    handler = Cu.waiveXrays(handler);
+    ext = Cu.waiveXrays(ext);
+
+    let sp = this;
+    let state = "uninitialized";
+    let extension = {
+      get state() {
+        return state;
+      },
+
+      startup() {
+        state = "pending";
+        return sp.sendQuery("SPStartupExtension", { id }).then(
+          () => {
+            state = "running";
+          },
+          () => {
+            state = "failed";
+            sp._extensionListeners.delete(listener);
+            return Promise.reject("startup failed");
+          }
+        );
+      },
+
+      unload() {
+        state = "unloading";
+        return sp.sendQuery("SPUnloadExtension", { id }).finally(() => {
+          sp._extensionListeners.delete(listener);
+          state = "unloaded";
+        });
+      },
+
+      sendMessage(...args) {
+        sp.sendAsyncMessage("SPExtensionMessage", { id, args });
+      },
+
+      grantActiveTab(tabId) {
+        sp.sendAsyncMessage("SPExtensionGrantActiveTab", { id, tabId });
+      },
+
+      terminateBackground(...args) {
+        return sp.sendQuery("SPExtensionTerminateBackground", { id, args });
+      },
+
+      wakeupBackground() {
+        return sp.sendQuery("SPExtensionWakeupBackground", { id });
+      },
+    };
+
+    this.sendAsyncMessage("SPLoadExtension", { ext, id });
+
+    let listener = msg => {
+      if (msg.data.id == id) {
+        if (msg.data.type == "extensionSetId") {
+          extension.id = msg.data.args[0];
+          extension.uuid = msg.data.args[1];
+        } else if (msg.data.type in handler) {
+          handler[msg.data.type](
+            ...Cu.cloneInto(msg.data.args, this.contentWindow)
+          );
+        } else {
+          dump(`Unexpected: ${msg.data.type}\n`);
+        }
+      }
+    };
+
+    this._extensionListeners.add(listener);
+    return extension;
+  }
+
+  invalidateExtensionStorageCache() {
+    this.notifyObserversInParentProcess(
+      null,
+      "extension-invalidate-storage-cache",
+      ""
+    );
+  }
+
+  allowMedia(window, enable) {
+    window.docShell.allowMedia = enable;
+  }
+
+  createChromeCache(name, url) {
+    let principal = this._getPrincipalFromArg(url);
+    return new this.contentWindow.CacheStorage(name, principal);
+  }
+
+  loadChannelAndReturnStatus(url, loadUsingSystemPrincipal) {
+    const BinaryInputStream = Components.Constructor(
+      "@mozilla.org/binaryinputstream;1",
+      "nsIBinaryInputStream",
+      "setInputStream"
+    );
+
+    return new Promise(function (resolve) {
+      let listener = {
+        httpStatus: 0,
+
+        onStartRequest(request) {
+          request.QueryInterface(Ci.nsIHttpChannel);
+          this.httpStatus = request.responseStatus;
+        },
+
+        onDataAvailable(request, stream, offset, count) {
+          new BinaryInputStream(stream).readByteArray(count);
+        },
+
+        onStopRequest(request, status) {
+          /* testing here that the redirect was not followed. If it was followed
+            we would see a http status of 200 and status of NS_OK */
+
+          let httpStatus = this.httpStatus;
+          resolve({ status, httpStatus });
+        },
+      };
+      let uri = lazy.NetUtil.newURI(url);
+      let channel = lazy.NetUtil.newChannel({ uri, loadUsingSystemPrincipal });
+
+      channel.loadFlags |= Ci.nsIChannel.LOAD_DOCUMENT_URI;
+      channel.QueryInterface(Ci.nsIHttpChannelInternal);
+      channel.documentURI = uri;
+      channel.asyncOpen(listener);
+    });
+  }
+
+  get ParserUtils() {
+    if (this._pu != null) {
+      return this._pu;
+    }
+
+    let pu = Cc["@mozilla.org/parserutils;1"].getService(Ci.nsIParserUtils);
+    // We need to create and return our own wrapper.
+    this._pu = {
+      sanitize(src, flags) {
+        return pu.sanitize(src, flags);
+      },
+      convertToPlainText(src, flags, wrapCol) {
+        return pu.convertToPlainText(src, flags, wrapCol);
+      },
+      parseFragment(fragment, flags, isXML, baseURL, element) {
+        let baseURI = baseURL ? lazy.NetUtil.newURI(baseURL) : null;
+        return pu.parseFragment(
+          lazy.WrapPrivileged.unwrap(fragment),
+          flags,
+          isXML,
+          baseURI,
+          lazy.WrapPrivileged.unwrap(element)
+        );
+      },
+    };
+    return this._pu;
+  }
+
+  createDOMWalker(node, showAnonymousContent) {
+    node = lazy.WrapPrivileged.unwrap(node);
+    let walker = Cc["@mozilla.org/inspector/deep-tree-walker;1"].createInstance(
+      Ci.inIDeepTreeWalker
+    );
+    walker.showAnonymousContent = showAnonymousContent;
+    walker.init(node.ownerDocument, NodeFilter.SHOW_ALL);
+    walker.currentNode = node;
+    let contentWindow = this.contentWindow;
+    return {
+      get firstChild() {
+        return lazy.WrapPrivileged.wrap(walker.firstChild(), contentWindow);
+      },
+      get lastChild() {
+        return lazy.WrapPrivileged.wrap(walker.lastChild(), contentWindow);
+      },
+    };
+  }
+
+  /**
+   * Which commands are available can be determined by checking which commands
+   * are registered. See \ref
+   * nsIControllerCommandTable.registerCommand(in String, in nsIControllerCommand).
+   */
+  doCommand(window, cmd, param) {
+    switch (cmd) {
+      case "cmd_align":
+      case "cmd_backgroundColor":
+      case "cmd_fontColor":
+      case "cmd_fontFace":
+      case "cmd_fontSize":
+      case "cmd_highlight":
+      case "cmd_insertImageNoUI":
+      case "cmd_insertLinkNoUI":
+      case "cmd_paragraphState": {
+        const params = Cu.createCommandParams();
+        params.setStringValue("state_attribute", param);
+        return window.docShell.doCommandWithParams(cmd, params);
+      }
+      case "cmd_pasteTransferable": {
+        const params = Cu.createCommandParams();
+        params.setISupportsValue("transferable", param);
+        return window.docShell.doCommandWithParams(cmd, params);
+      }
+      default:
+        return window.docShell.doCommand(cmd);
+    }
+  }
+
+  isCommandEnabled(window, cmd) {
+    return window.docShell.isCommandEnabled(cmd);
+  }
+
+  /**
+   * See \ref nsIDocumentViewerEdit.setCommandNode(in Node).
+   */
+  setCommandNode(window, node) {
+    return window.docShell.docViewer
+      .QueryInterface(Ci.nsIDocumentViewerEdit)
+      .setCommandNode(node);
+  }
+
+  /* Bug 1339006 Runnables of nsIURIClassifier.classify may be labeled by
+   * SystemGroup, but some test cases may run as web content. That would assert
+   * when trying to enter web content from a runnable labeled by the
+   * SystemGroup. To avoid that, we run classify from SpecialPowers which is
+   * chrome-privileged and allowed to run inside SystemGroup
+   */
+
+  doUrlClassify(principal, callback) {
+    let classifierService = Cc[
+      "@mozilla.org/url-classifier/dbservice;1"
+    ].getService(Ci.nsIURIClassifier);
+
+    let wrapCallback = (...args) => {
+      Services.tm.dispatchToMainThread(() => {
+        if (typeof callback == "function") {
+          callback(...args);
+        } else {
+          callback.onClassifyComplete.call(undefined, ...args);
+        }
+      });
+    };
+
+    return classifierService.classify(
+      lazy.WrapPrivileged.unwrap(principal),
+      wrapCallback
+    );
+  }
+
+  // TODO: Bug 1353701 - Supports custom event target for labelling.
+  doUrlClassifyLocal(uri, tables, callback) {
+    let classifierService = Cc[
+      "@mozilla.org/url-classifier/dbservice;1"
+    ].getService(Ci.nsIURIClassifier);
+
+    let wrapCallback = results => {
+      Services.tm.dispatchToMainThread(() => {
+        if (typeof callback == "function") {
+          callback(lazy.WrapPrivileged.wrap(results, this.contentWindow));
+        } else {
+          callback.onClassifyComplete.call(
+            undefined,
+            lazy.WrapPrivileged.wrap(results, this.contentWindow)
+          );
+        }
+      });
+    };
+
+    let feature = classifierService.createFeatureWithTables(
+      "test",
+      tables.split(","),
+      []
+    );
+    return classifierService.asyncClassifyLocalWithFeatures(
+      lazy.WrapPrivileged.unwrap(uri),
+      [feature],
+      Ci.nsIUrlClassifierFeature.blocklist,
+      wrapCallback
+    );
+  }
+
+  /* Content processes asynchronously receive child-to-parent transformations
+   * when they are launched.  Until they are received, screen coordinates
+   * reported to JS are wrong.  This is generally ok.  It behaves as if the
+   * user repositioned the window.  But if we want to test screen coordinates,
+   * we need to wait for the updated data.
+   */
+  contentTransformsReceived(win) {
+    while (win) {
+      try {
+        return win.docShell.browserChild.contentTransformsReceived();
+      } catch (ex) {
+        // browserChild getter throws on non-e10s rather than returning null.
+      }
+      if (win == win.parent) {
+        break;
+      }
+      win = win.parent;
+    }
+    return Promise.resolve();
+  }
+}
+
+SpecialPowersChild.prototype._proxiedObservers = {
+  "specialpowers-http-notify-request": function (aMessage) {
+    let uri = aMessage.json.uri;
+    Services.obs.notifyObservers(
+      null,
+      "specialpowers-http-notify-request",
+      uri
+    );
+  },
+
+  "specialpowers-service-worker-shutdown": function (aMessage) {
+    Services.obs.notifyObservers(null, "specialpowers-service-worker-shutdown");
+  },
+
+  "specialpowers-csp-on-violate-policy": function (aMessage) {
+    let subject = null;
+
+    try {
+      subject = Services.io.newURI(aMessage.data.subject);
+    } catch (ex) {
+      // if it's not a valid URI it must be an nsISupportsCString
+      subject = Cc["@mozilla.org/supports-cstring;1"].createInstance(
+        Ci.nsISupportsCString
+      );
+      subject.data = aMessage.data.subject;
+    }
+    Services.obs.notifyObservers(
+      subject,
+      "specialpowers-csp-on-violate-policy",
+      aMessage.data.data
+    );
+  },
+
+  "specialpowers-xfo-on-violate-policy": function (aMessage) {
+    let subject = Services.io.newURI(aMessage.data.subject);
+    Services.obs.notifyObservers(
+      subject,
+      "specialpowers-xfo-on-violate-policy",
+      aMessage.data.data
+    );
+  },
+};
+
+SpecialPowersChild.prototype.EARLY_BETA_OR_EARLIER =
+  AppConstants.EARLY_BETA_OR_EARLIER;
diff --git a/testing/specialpowers/content/SpecialPowersEventUtils.sys.mjs b/testing/specialpowers/content/SpecialPowersEventUtils.sys.mjs
new file mode 100644
index 0000000000..68cec2b6e3
--- /dev/null
+++ b/testing/specialpowers/content/SpecialPowersEventUtils.sys.mjs
@@ -0,0 +1,35 @@
+/* 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/. */
+
+/**
+ * Loads a stub copy of EventUtils.js which can be used by things like
+ * content tasks without holding any direct references to windows.
+ */
+
+import { setTimeout } from "resource://gre/modules/Timer.sys.mjs";
+
+export let EventUtils = { setTimeout, window: {}, _EU_Ci: Ci, _EU_Cc: Cc };
+
+EventUtils.parent = EventUtils.window;
+
+EventUtils.synthesizeClick = element =>
+  new Promise(resolve => {
+    element.addEventListener("click", () => resolve(), { once: true });
+
+    EventUtils.synthesizeMouseAtCenter(
+      element,
+      { type: "mousedown", isSynthesized: false },
+      element.ownerGlobal
+    );
+    EventUtils.synthesizeMouseAtCenter(
+      element,
+      { type: "mouseup", isSynthesized: false },
+      element.ownerGlobal
+    );
+  });
+
+Services.scriptloader.loadSubScript(
+  "chrome://mochikit/content/tests/SimpleTest/EventUtils.js",
+  EventUtils
+);
diff --git a/testing/specialpowers/content/SpecialPowersParent.sys.mjs b/testing/specialpowers/content/SpecialPowersParent.sys.mjs
new file mode 100644
index 0000000000..3ed660d71c
--- /dev/null
+++ b/testing/specialpowers/content/SpecialPowersParent.sys.mjs
@@ -0,0 +1,1470 @@
+/* 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/. */
+
+import { AppConstants } from "resource://gre/modules/AppConstants.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  ExtensionData: "resource://gre/modules/Extension.sys.mjs",
+  ExtensionTestCommon: "resource://testing-common/ExtensionTestCommon.sys.mjs",
+  HiddenFrame: "resource://gre/modules/HiddenFrame.sys.mjs",
+  PerTestCoverageUtils:
+    "resource://testing-common/PerTestCoverageUtils.sys.mjs",
+  ServiceWorkerCleanUp: "resource://gre/modules/ServiceWorkerCleanUp.sys.mjs",
+  SpecialPowersSandbox:
+    "resource://testing-common/SpecialPowersSandbox.sys.mjs",
+});
+
+class SpecialPowersError extends Error {
+  get name() {
+    return "SpecialPowersError";
+  }
+}
+
+const PREF_TYPES = {
+  [Ci.nsIPrefBranch.PREF_INVALID]: "INVALID",
+  [Ci.nsIPrefBranch.PREF_INT]: "INT",
+  [Ci.nsIPrefBranch.PREF_BOOL]: "BOOL",
+  [Ci.nsIPrefBranch.PREF_STRING]: "STRING",
+  number: "INT",
+  boolean: "BOOL",
+  string: "STRING",
+};
+
+// We share a single preference environment stack between all
+// SpecialPowers instances, across all processes.
+let prefUndoStack = [];
+let inPrefEnvOp = false;
+
+let permissionUndoStack = [];
+
+function doPrefEnvOp(fn) {
+  if (inPrefEnvOp) {
+    throw new Error(
+      "Reentrant preference environment operations not supported"
+    );
+  }
+  inPrefEnvOp = true;
+  try {
+    return fn();
+  } finally {
+    inPrefEnvOp = false;
+  }
+}
+
+async function createWindowlessBrowser({ isPrivate = false } = {}) {
+  const { promiseDocumentLoaded, promiseEvent, promiseObserved } =
+    ChromeUtils.importESModule(
+      "resource://gre/modules/ExtensionUtils.sys.mjs"
+    ).ExtensionUtils;
+
+  let windowlessBrowser = Services.appShell.createWindowlessBrowser(true);
+
+  if (isPrivate) {
+    let loadContext = windowlessBrowser.docShell.QueryInterface(
+      Ci.nsILoadContext
+    );
+    loadContext.usePrivateBrowsing = true;
+  }
+
+  let chromeShell = windowlessBrowser.docShell.QueryInterface(
+    Ci.nsIWebNavigation
+  );
+
+  const system = Services.scriptSecurityManager.getSystemPrincipal();
+  chromeShell.createAboutBlankDocumentViewer(system, system);
+  windowlessBrowser.browsingContext.useGlobalHistory = false;
+  chromeShell.loadURI(
+    Services.io.newURI("chrome://extensions/content/dummy.xhtml"),
+    {
+      triggeringPrincipal: system,
+    }
+  );
+
+  await promiseObserved(
+    "chrome-document-global-created",
+    win => win.document == chromeShell.document
+  );
+
+  let chromeDoc = await promiseDocumentLoaded(chromeShell.document);
+
+  let browser = chromeDoc.createXULElement("browser");
+  browser.setAttribute("type", "content");
+  browser.setAttribute("disableglobalhistory", "true");
+  browser.setAttribute("remote", "true");
+
+  let promise = promiseEvent(browser, "XULFrameLoaderCreated");
+  chromeDoc.documentElement.appendChild(browser);
+
+  await promise;
+
+  return { windowlessBrowser, browser };
+}
+
+// Supplies the unique IDs for tasks created by SpecialPowers.spawn(),
+// used to bounce assertion messages back down to the correct child.
+let nextTaskID = 1;
+
+// The default actor to send assertions to if a task originated in a
+// window without a test harness.
+let defaultAssertHandler;
+
+export class SpecialPowersParent extends JSWindowActorParent {
+  constructor() {
+    super();
+
+    this._messageManager = Services.mm;
+    this._serviceWorkerListener = null;
+
+    this._observer = this.observe.bind(this);
+
+    this.didDestroy = this.uninit.bind(this);
+
+    this._registerObservers = {
+      _self: this,
+      _topics: [],
+      _add(topic) {
+        if (!this._topics.includes(topic)) {
+          this._topics.push(topic);
+          Services.obs.addObserver(this, topic);
+        }
+      },
+      observe(aSubject, aTopic, aData) {
+        var msg = { aData };
+        switch (aTopic) {
+          case "csp-on-violate-policy":
+            // the subject is either an nsIURI or an nsISupportsCString
+            let subject = null;
+            if (aSubject instanceof Ci.nsIURI) {
+              subject = aSubject.asciiSpec;
+            } else if (aSubject instanceof Ci.nsISupportsCString) {
+              subject = aSubject.data;
+            } else {
+              throw new Error("Subject must be nsIURI or nsISupportsCString");
+            }
+            msg = {
+              subject,
+              data: aData,
+            };
+            this._self.sendAsyncMessage("specialpowers-" + aTopic, msg);
+            return;
+          case "xfo-on-violate-policy":
+            let uriSpec = null;
+            if (aSubject instanceof Ci.nsIURI) {
+              uriSpec = aSubject.asciiSpec;
+            } else {
+              throw new Error("Subject must be nsIURI");
+            }
+            msg = {
+              subject: uriSpec,
+              data: aData,
+            };
+            this._self.sendAsyncMessage("specialpowers-" + aTopic, msg);
+            return;
+          default:
+            this._self.sendAsyncMessage("specialpowers-" + aTopic, msg);
+        }
+      },
+    };
+
+    this._basePrefs = null;
+    this.init();
+
+    this._crashDumpDir = null;
+    this._processCrashObserversRegistered = false;
+    this._chromeScriptListeners = [];
+    this._extensions = new Map();
+    this._taskActors = new Map();
+  }
+
+  static registerActor() {
+    ChromeUtils.registerWindowActor("SpecialPowers", {
+      allFrames: true,
+      includeChrome: true,
+      child: {
+        esModuleURI: "resource://testing-common/SpecialPowersChild.sys.mjs",
+        observers: [
+          "chrome-document-global-created",
+          "content-document-global-created",
+        ],
+      },
+      parent: {
+        esModuleURI: "resource://testing-common/SpecialPowersParent.sys.mjs",
+      },
+    });
+  }
+
+  static unregisterActor() {
+    ChromeUtils.unregisterWindowActor("SpecialPowers");
+  }
+
+  init() {
+    Services.obs.addObserver(this._observer, "http-on-modify-request");
+
+    // We would like to check that tests don't leave service workers around
+    // after they finish, but that information lives in the parent process.
+    // Ideally, we'd be able to tell the child processes whenever service
+    // workers are registered or unregistered so they would know at all times,
+    // but service worker lifetimes are complicated enough to make that
+    // difficult. For the time being, let the child process know when a test
+    // registers a service worker so it can ask, synchronously, at the end if
+    // the service worker had unregister called on it.
+    let swm = Cc["@mozilla.org/serviceworkers/manager;1"].getService(
+      Ci.nsIServiceWorkerManager
+    );
+    let self = this;
+    this._serviceWorkerListener = {
+      onRegister() {
+        self.onRegister();
+      },
+
+      onUnregister() {
+        // no-op
+      },
+    };
+    swm.addListener(this._serviceWorkerListener);
+
+    this.getBaselinePrefs();
+  }
+
+  uninit() {
+    if (defaultAssertHandler === this) {
+      defaultAssertHandler = null;
+    }
+
+    var obs = Services.obs;
+    obs.removeObserver(this._observer, "http-on-modify-request");
+    this._registerObservers._topics.splice(0).forEach(element => {
+      obs.removeObserver(this._registerObservers, element);
+    });
+    this._removeProcessCrashObservers();
+
+    let swm = Cc["@mozilla.org/serviceworkers/manager;1"].getService(
+      Ci.nsIServiceWorkerManager
+    );
+    swm.removeListener(this._serviceWorkerListener);
+  }
+
+  observe(aSubject, aTopic, aData) {
+    function addDumpIDToMessage(propertyName) {
+      try {
+        var id = aSubject.getPropertyAsAString(propertyName);
+      } catch (ex) {
+        id = null;
+      }
+      if (id) {
+        message.dumpIDs.push({ id, extension: "dmp" });
+        message.dumpIDs.push({ id, extension: "extra" });
+      }
+    }
+
+    switch (aTopic) {
+      case "http-on-modify-request":
+        if (aSubject instanceof Ci.nsIChannel) {
+          let uri = aSubject.URI.spec;
+          this.sendAsyncMessage("specialpowers-http-notify-request", { uri });
+        }
+        break;
+
+      case "ipc:content-shutdown":
+        aSubject = aSubject.QueryInterface(Ci.nsIPropertyBag2);
+        if (!aSubject.hasKey("abnormal")) {
+          return; // This is a normal shutdown, ignore it
+        }
+
+        var message = { type: "crash-observed", dumpIDs: [] };
+        addDumpIDToMessage("dumpID");
+        this.sendAsyncMessage("SPProcessCrashService", message);
+        break;
+    }
+  }
+
+  _getCrashDumpDir() {
+    if (!this._crashDumpDir) {
+      this._crashDumpDir = Services.dirsvc.get("ProfD", Ci.nsIFile);
+      this._crashDumpDir.append("minidumps");
+    }
+    return this._crashDumpDir;
+  }
+
+  _getPendingCrashDumpDir() {
+    if (!this._pendingCrashDumpDir) {
+      this._pendingCrashDumpDir = Services.dirsvc.get("UAppData", Ci.nsIFile);
+      this._pendingCrashDumpDir.append("Crash Reports");
+      this._pendingCrashDumpDir.append("pending");
+    }
+    return this._pendingCrashDumpDir;
+  }
+
+  _deleteCrashDumpFiles(aFilenames) {
+    var crashDumpDir = this._getCrashDumpDir();
+    if (!crashDumpDir.exists()) {
+      return false;
+    }
+
+    var success = !!aFilenames.length;
+    aFilenames.forEach(function (crashFilename) {
+      var file = crashDumpDir.clone();
+      file.append(crashFilename);
+      if (file.exists()) {
+        file.remove(false);
+      } else {
+        success = false;
+      }
+    });
+    return success;
+  }
+
+  _findCrashDumpFiles(aToIgnore) {
+    var crashDumpDir = this._getCrashDumpDir();
+    var entries = crashDumpDir.exists() && crashDumpDir.directoryEntries;
+    if (!entries) {
+      return [];
+    }
+
+    var crashDumpFiles = [];
+    while (entries.hasMoreElements()) {
+      var file = entries.nextFile;
+      var path = String(file.path);
+      if (path.match(/\.(dmp|extra)$/) && !aToIgnore[path]) {
+        crashDumpFiles.push(path);
+      }
+    }
+    return crashDumpFiles.concat();
+  }
+
+  _deletePendingCrashDumpFiles() {
+    var crashDumpDir = this._getPendingCrashDumpDir();
+    var removed = false;
+    if (crashDumpDir.exists()) {
+      let entries = crashDumpDir.directoryEntries;
+      while (entries.hasMoreElements()) {
+        let file = entries.nextFile;
+        if (file.isFile()) {
+          file.remove(false);
+          removed = true;
+        }
+      }
+    }
+    return removed;
+  }
+
+  _addProcessCrashObservers() {
+    if (this._processCrashObserversRegistered) {
+      return;
+    }
+
+    Services.obs.addObserver(this._observer, "ipc:content-shutdown");
+    this._processCrashObserversRegistered = true;
+  }
+
+  _removeProcessCrashObservers() {
+    if (!this._processCrashObserversRegistered) {
+      return;
+    }
+
+    Services.obs.removeObserver(this._observer, "ipc:content-shutdown");
+    this._processCrashObserversRegistered = false;
+  }
+
+  onRegister() {
+    this.sendAsyncMessage("SPServiceWorkerRegistered", { registered: true });
+  }
+
+  _getURI(url) {
+    return Services.io.newURI(url);
+  }
+  _notifyCategoryAndObservers(subject, topic, data) {
+    const serviceMarker = "service,";
+
+    // First create observers from the category manager.
+
+    let observers = [];
+
+    for (let { value: contractID } of Services.catMan.enumerateCategory(
+      topic
+    )) {
+      let factoryFunction;
+      if (contractID.substring(0, serviceMarker.length) == serviceMarker) {
+        contractID = contractID.substring(serviceMarker.length);
+        factoryFunction = "getService";
+      } else {
+        factoryFunction = "createInstance";
+      }
+
+      try {
+        let handler = Cc[contractID][factoryFunction]();
+        if (handler) {
+          let observer = handler.QueryInterface(Ci.nsIObserver);
+          observers.push(observer);
+        }
+      } catch (e) {}
+    }
+
+    // Next enumerate the registered observers.
+    for (let observer of Services.obs.enumerateObservers(topic)) {
+      if (observer instanceof Ci.nsIObserver && !observers.includes(observer)) {
+        observers.push(observer);
+      }
+    }
+
+    observers.forEach(function (observer) {
+      try {
+        observer.observe(subject, topic, data);
+      } catch (e) {}
+    });
+  }
+
+  /*
+    Iterate through one atomic set of pref actions and perform sets/clears as appropriate.
+    All actions performed must modify the relevant pref.
+
+    Returns whether we need to wait for a refresh driver tick for the pref to
+    have effect. This is only needed for ui. and font. prefs, which affect the
+    look and feel code and have some change-coalescing going on.
+  */
+  _applyPrefs(actions) {
+    let requiresRefresh = false;
+    for (let pref of actions) {
+      // This logic should match PrefRequiresRefresh in reftest.sys.mjs
+      requiresRefresh =
+        requiresRefresh ||
+        pref.name == "layout.css.prefers-color-scheme.content-override" ||
+        pref.name.startsWith("ui.") ||
+        pref.name.startsWith("browser.display.") ||
+        pref.name.startsWith("font.");
+      if (pref.action == "set") {
+        this._setPref(pref.name, pref.type, pref.value, pref.iid);
+      } else if (pref.action == "clear") {
+        Services.prefs.clearUserPref(pref.name);
+      }
+    }
+    return requiresRefresh;
+  }
+
+  /**
+   * Take in a list of pref changes to make, pushes their current values
+   * onto the restore stack, and makes the changes.  When the test
+   * finishes, these changes are reverted.
+   *
+   * |inPrefs| must be an object with up to two properties: "set" and "clear".
+   * pushPrefEnv will set prefs as indicated in |inPrefs.set| and will unset
+   * the prefs indicated in |inPrefs.clear|.
+   *
+   * For example, you might pass |inPrefs| as:
+   *
+   *  inPrefs = {'set': [['foo.bar', 2], ['magic.pref', 'baz']],
+   *             'clear': [['clear.this'], ['also.this']] };
+   *
+   * Notice that |set| and |clear| are both an array of arrays.  In |set|, each
+   * of the inner arrays must have the form [pref_name, value] or [pref_name,
+   * value, iid].  (The latter form is used for prefs with "complex" values.)
+   *
+   * In |clear|, each inner array should have the form [pref_name].
+   *
+   * If you set the same pref more than once (or both set and clear a pref),
+   * the behavior of this method is undefined.
+   */
+  pushPrefEnv(inPrefs) {
+    return doPrefEnvOp(() => {
+      let pendingActions = [];
+      let cleanupActions = [];
+
+      for (let [action, prefs] of Object.entries(inPrefs)) {
+        for (let pref of prefs) {
+          let name = pref[0];
+          let value = null;
+          let iid = null;
+          let type = PREF_TYPES[Services.prefs.getPrefType(name)];
+          let originalValue = null;
+
+          if (pref.length == 3) {
+            value = pref[1];
+            iid = pref[2];
+          } else if (pref.length == 2) {
+            value = pref[1];
+          }
+
+          /* If pref is not found or invalid it doesn't exist. */
+          if (type !== "INVALID") {
+            if (
+              (Services.prefs.prefHasUserValue(name) && action == "clear") ||
+              action == "set"
+            ) {
+              originalValue = this._getPref(name, type);
+            }
+          } else if (action == "set") {
+            /* name doesn't exist, so 'clear' is pointless */
+            if (iid) {
+              type = "COMPLEX";
+            }
+          }
+
+          if (type === "INVALID") {
+            type = PREF_TYPES[typeof value];
+          }
+          if (type === "INVALID") {
+            throw new Error("Unexpected preference type for " + name);
+          }
+
+          pendingActions.push({ action, type, name, value, iid });
+
+          /* Push original preference value or clear into cleanup array */
+          var cleanupTodo = { type, name, value: originalValue, iid };
+          if (originalValue == null) {
+            cleanupTodo.action = "clear";
+          } else {
+            cleanupTodo.action = "set";
+          }
+          cleanupActions.push(cleanupTodo);
+        }
+      }
+
+      prefUndoStack.push(cleanupActions);
+      let requiresRefresh = this._applyPrefs(pendingActions);
+      return { requiresRefresh };
+    });
+  }
+
+  async popPrefEnv() {
+    return doPrefEnvOp(() => {
+      let env = prefUndoStack.pop();
+      if (env) {
+        let requiresRefresh = this._applyPrefs(env);
+        return { popped: true, requiresRefresh };
+      }
+      return { popped: false, requiresRefresh: false };
+    });
+  }
+
+  flushPrefEnv() {
+    let requiresRefresh = false;
+    while (prefUndoStack.length) {
+      requiresRefresh |= this.popPrefEnv().requiresRefresh;
+    }
+    return { requiresRefresh };
+  }
+
+  _setPref(name, type, value, iid) {
+    switch (type) {
+      case "BOOL":
+        return Services.prefs.setBoolPref(name, value);
+      case "INT":
+        return Services.prefs.setIntPref(name, value);
+      case "CHAR":
+        return Services.prefs.setCharPref(name, value);
+      case "COMPLEX":
+        return Services.prefs.setComplexValue(name, iid, value);
+      case "STRING":
+        return Services.prefs.setStringPref(name, value);
+    }
+    switch (typeof value) {
+      case "boolean":
+        return Services.prefs.setBoolPref(name, value);
+      case "number":
+        return Services.prefs.setIntPref(name, value);
+      case "string":
+        return Services.prefs.setStringPref(name, value);
+    }
+    throw new Error(
+      `Unexpected preference type: ${type} for ${name} with value ${value} and type ${typeof value}`
+    );
+  }
+
+  _getPref(name, type, defaultValue, iid) {
+    switch (type) {
+      case "BOOL":
+        if (defaultValue !== undefined) {
+          return Services.prefs.getBoolPref(name, defaultValue);
+        }
+        return Services.prefs.getBoolPref(name);
+      case "INT":
+        if (defaultValue !== undefined) {
+          return Services.prefs.getIntPref(name, defaultValue);
+        }
+        return Services.prefs.getIntPref(name);
+      case "CHAR":
+        if (defaultValue !== undefined) {
+          return Services.prefs.getCharPref(name, defaultValue);
+        }
+        return Services.prefs.getCharPref(name);
+      case "COMPLEX":
+        return Services.prefs.getComplexValue(name, iid);
+      case "STRING":
+        if (defaultValue !== undefined) {
+          return Services.prefs.getStringPref(name, defaultValue);
+        }
+        return Services.prefs.getStringPref(name);
+    }
+    throw new Error(
+      `Unexpected preference type: ${type} for preference ${name}`
+    );
+  }
+
+  getBaselinePrefs() {
+    this._basePrefs = this._getAllPreferences();
+  }
+
+  _comparePrefs(base, target, ignorePrefs, partialMatches) {
+    let failures = [];
+    for (const [key, value] of base) {
+      if (ignorePrefs.includes(key)) {
+        continue;
+      }
+      let partialFind = false;
+      partialMatches.forEach(pm => {
+        if (key.startsWith(pm)) {
+          partialFind = true;
+        }
+      });
+      if (partialFind) {
+        continue;
+      }
+
+      if (value === target.get(key)) {
+        continue;
+      }
+      if (!failures.includes(key)) {
+        failures.push(key);
+      }
+    }
+    return failures;
+  }
+
+  comparePrefsToBaseline(ignorePrefs) {
+    let newPrefs = this._getAllPreferences();
+
+    // find all items in ignorePrefs that end in *, add to partialMatch
+    let partialMatch = [];
+    if (ignorePrefs === undefined) {
+      ignorePrefs = [];
+    }
+    ignorePrefs.forEach(pref => {
+      if (pref.endsWith("*")) {
+        partialMatch.push(pref.split("*")[0]);
+      }
+    });
+
+    // find all new prefs different than old
+    let rv1 = this._comparePrefs(
+      newPrefs,
+      this._basePrefs,
+      ignorePrefs,
+      partialMatch
+    );
+
+    // find all old prefs different than new (in case we delete)
+    let rv2 = this._comparePrefs(
+      this._basePrefs,
+      newPrefs,
+      ignorePrefs,
+      partialMatch
+    );
+
+    let failures = [...new Set([...rv1, ...rv2])];
+
+    // reset failures
+    failures.forEach(f => {
+      if (this._basePrefs.get(f)) {
+        this._setPref(
+          f,
+          PREF_TYPES[Services.prefs.getPrefType(f)],
+          this._basePrefs.get(f)
+        );
+      } else {
+        Services.prefs.clearUserPref(f);
+      }
+    });
+
+    if (ignorePrefs.length > 1) {
+      return failures;
+    }
+    return [];
+  }
+
+  _getAllPreferences() {
+    let names = new Map();
+    for (let prefName of Services.prefs.getChildList("")) {
+      let prefType = PREF_TYPES[Services.prefs.getPrefType(prefName)];
+      let prefValue = this._getPref(prefName, prefType);
+      names.set(prefName, prefValue);
+    }
+    return names;
+  }
+
+  _toggleMuteAudio(aMuted) {
+    let browser = this.browsingContext.top.embedderElement;
+    if (aMuted) {
+      browser.mute();
+    } else {
+      browser.unmute();
+    }
+  }
+
+  _permOp(perm) {
+    switch (perm.op) {
+      case "add":
+        Services.perms.addFromPrincipal(
+          perm.principal,
+          perm.type,
+          perm.permission,
+          perm.expireType,
+          perm.expireTime
+        );
+        break;
+      case "remove":
+        Services.perms.removeFromPrincipal(perm.principal, perm.type);
+        break;
+      default:
+        throw new Error(`Unexpected permission op: ${perm.op}`);
+    }
+  }
+
+  pushPermissions(inPermissions) {
+    let pendingPermissions = [];
+    let cleanupPermissions = [];
+
+    for (let permission of inPermissions) {
+      let { principal } = permission;
+      if (principal.isSystemPrincipal) {
+        continue;
+      }
+
+      let originalValue = Services.perms.testPermissionFromPrincipal(
+        principal,
+        permission.type
+      );
+
+      let perm = permission.allow;
+      if (typeof perm === "boolean") {
+        perm = Ci.nsIPermissionManager[perm ? "ALLOW_ACTION" : "DENY_ACTION"];
+      }
+
+      if (permission.remove) {
+        perm = Ci.nsIPermissionManager.UNKNOWN_ACTION;
+      }
+
+      if (originalValue == perm) {
+        continue;
+      }
+
+      let todo = {
+        op: "add",
+        type: permission.type,
+        permission: perm,
+        value: perm,
+        principal,
+        expireType:
+          typeof permission.expireType === "number" ? permission.expireType : 0, // default: EXPIRE_NEVER
+        expireTime:
+          typeof permission.expireTime === "number" ? permission.expireTime : 0,
+      };
+
+      var cleanupTodo = Object.assign({}, todo);
+
+      if (permission.remove) {
+        todo.op = "remove";
+      }
+
+      pendingPermissions.push(todo);
+
+      if (originalValue == Ci.nsIPermissionManager.UNKNOWN_ACTION) {
+        cleanupTodo.op = "remove";
+      } else {
+        cleanupTodo.value = originalValue;
+        cleanupTodo.permission = originalValue;
+      }
+      cleanupPermissions.push(cleanupTodo);
+    }
+
+    permissionUndoStack.push(cleanupPermissions);
+
+    for (let perm of pendingPermissions) {
+      this._permOp(perm);
+    }
+  }
+
+  popPermissions() {
+    if (permissionUndoStack.length) {
+      for (let perm of permissionUndoStack.pop()) {
+        this._permOp(perm);
+      }
+    }
+  }
+
+  flushPermissions() {
+    while (permissionUndoStack.length) {
+      this.popPermissions();
+    }
+  }
+
+  _spawnChrome(task, args, caller, imports) {
+    let sb = new lazy.SpecialPowersSandbox(
+      null,
+      data => {
+        this.sendAsyncMessage("Assert", data);
+      },
+      { imports }
+    );
+
+    for (let [global, prop] of Object.entries({
+      windowGlobalParent: "manager",
+      browsingContext: "browsingContext",
+    })) {
+      Object.defineProperty(sb.sandbox, global, {
+        get: () => {
+          return this[prop];
+        },
+        enumerable: true,
+      });
+    }
+
+    return sb.execute(task, args, caller);
+  }
+
+  /**
+   * messageManager callback function
+   * This will get requests from our API in the window and process them in chrome for it
+   **/
+  // eslint-disable-next-line complexity
+  async receiveMessage(aMessage) {
+    let startTime = Cu.now();
+    // Try block so we can use a finally statement to add a profiler marker
+    // despite all the return statements.
+    try {
+      // We explicitly return values in the below code so that this function
+      // doesn't trigger a flurry of warnings about "does not always return
+      // a value".
+      switch (aMessage.name) {
+        case "SPToggleMuteAudio":
+          return this._toggleMuteAudio(aMessage.data.mute);
+
+        case "Ping":
+          return undefined;
+
+        case "SpecialPowers.Quit":
+          if (
+            !AppConstants.RELEASE_OR_BETA &&
+            !AppConstants.DEBUG &&
+            !AppConstants.MOZ_CODE_COVERAGE &&
+            !AppConstants.ASAN &&
+            !AppConstants.TSAN
+          ) {
+            if (Services.profiler.IsActive()) {
+              let filename = Services.env.get("MOZ_PROFILER_SHUTDOWN");
+              if (filename) {
+                await Services.profiler.dumpProfileToFileAsync(filename);
+                await Services.profiler.StopProfiler();
+              }
+            }
+            Cu.exitIfInAutomation();
+          } else {
+            Services.startup.quit(Ci.nsIAppStartup.eForceQuit);
+          }
+          return undefined;
+
+        case "EnsureFocus":
+          let bc = aMessage.data.browsingContext;
+          // Send a message to the child telling it to focus the window.
+          // If the message responds with a browsing context, then
+          // a child browsing context in a subframe should be focused.
+          // Iterate until nothing is returned and we get to the most
+          // deeply nested subframe that should be focused.
+          do {
+            let spParent = bc.currentWindowGlobal.getActor("SpecialPowers");
+            if (spParent) {
+              bc = await spParent.sendQuery("EnsureFocus", {
+                blurSubframe: aMessage.data.blurSubframe,
+              });
+            }
+          } while (bc && !aMessage.data.blurSubframe);
+          return undefined;
+
+        case "SpecialPowers.Focus":
+          if (this.manager.rootFrameLoader) {
+            this.manager.rootFrameLoader.ownerElement.focus();
+          }
+          return undefined;
+
+        case "SpecialPowers.CreateFiles":
+          return (async () => {
+            let filePaths = [];
+            if (!this._createdFiles) {
+              this._createdFiles = [];
+            }
+            let createdFiles = this._createdFiles;
+
+            let promises = [];
+            aMessage.data.forEach(function (request) {
+              const filePerms = 0o666;
+              let testFile = Services.dirsvc.get("ProfD", Ci.nsIFile);
+              if (request.name) {
+                testFile.appendRelativePath(request.name);
+              } else {
+                testFile.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, filePerms);
+              }
+              let outStream = Cc[
+                "@mozilla.org/network/file-output-stream;1"
+              ].createInstance(Ci.nsIFileOutputStream);
+              outStream.init(
+                testFile,
+                0x02 | 0x08 | 0x20, // PR_WRONLY | PR_CREATE_FILE | PR_TRUNCATE
+                filePerms,
+                0
+              );
+              if (request.data) {
+                outStream.write(request.data, request.data.length);
+              }
+              outStream.close();
+              promises.push(
+                File.createFromFileName(testFile.path, request.options).then(
+                  function (file) {
+                    filePaths.push(file);
+                  }
+                )
+              );
+              createdFiles.push(testFile);
+            });
+
+            await Promise.all(promises);
+            return filePaths;
+          })().catch(e => {
+            console.error(e);
+            return Promise.reject(String(e));
+          });
+
+        case "SpecialPowers.RemoveFiles":
+          if (this._createdFiles) {
+            this._createdFiles.forEach(function (testFile) {
+              try {
+                testFile.remove(false);
+              } catch (e) {}
+            });
+            this._createdFiles = null;
+          }
+          return undefined;
+
+        case "Wakeup":
+          return undefined;
+
+        case "EvictAllDocumentViewers":
+          this.browsingContext.top.sessionHistory.evictAllDocumentViewers();
+          return undefined;
+
+        case "getBaselinePrefs":
+          return this.getBaselinePrefs();
+
+        case "comparePrefsToBaseline":
+          return this.comparePrefsToBaseline(aMessage.data);
+
+        case "PushPrefEnv":
+          return this.pushPrefEnv(aMessage.data);
+
+        case "PopPrefEnv":
+          return this.popPrefEnv();
+
+        case "FlushPrefEnv":
+          return this.flushPrefEnv();
+
+        case "PushPermissions":
+          return this.pushPermissions(aMessage.data);
+
+        case "PopPermissions":
+          return this.popPermissions();
+
+        case "FlushPermissions":
+          return this.flushPermissions();
+
+        case "SPPrefService": {
+          let prefs = Services.prefs;
+          let prefType = aMessage.json.prefType.toUpperCase();
+          let { prefName, prefValue, iid, defaultValue } = aMessage.json;
+
+          if (aMessage.json.op == "get") {
+            if (!prefName || !prefType) {
+              throw new SpecialPowersError(
+                "Invalid parameters for get in SPPrefService"
+              );
+            }
+
+            // return null if the pref doesn't exist
+            if (
+              defaultValue === undefined &&
+              prefs.getPrefType(prefName) == prefs.PREF_INVALID
+            ) {
+              return null;
+            }
+            return this._getPref(prefName, prefType, defaultValue, iid);
+          } else if (aMessage.json.op == "set") {
+            if (!prefName || !prefType || prefValue === undefined) {
+              throw new SpecialPowersError(
+                "Invalid parameters for set in SPPrefService"
+              );
+            }
+
+            return this._setPref(prefName, prefType, prefValue, iid);
+          } else if (aMessage.json.op == "clear") {
+            if (!prefName) {
+              throw new SpecialPowersError(
+                "Invalid parameters for clear in SPPrefService"
+              );
+            }
+
+            prefs.clearUserPref(prefName);
+          } else {
+            throw new SpecialPowersError("Invalid operation for SPPrefService");
+          }
+
+          return undefined; // See comment at the beginning of this function.
+        }
+
+        case "SPProcessCrashService": {
+          switch (aMessage.json.op) {
+            case "register-observer":
+              this._addProcessCrashObservers();
+              break;
+            case "unregister-observer":
+              this._removeProcessCrashObservers();
+              break;
+            case "delete-crash-dump-files":
+              return this._deleteCrashDumpFiles(aMessage.json.filenames);
+            case "find-crash-dump-files":
+              return this._findCrashDumpFiles(
+                aMessage.json.crashDumpFilesToIgnore
+              );
+            case "delete-pending-crash-dump-files":
+              return this._deletePendingCrashDumpFiles();
+            default:
+              throw new SpecialPowersError(
+                "Invalid operation for SPProcessCrashService"
+              );
+          }
+          return undefined; // See comment at the beginning of this function.
+        }
+
+        case "SPProcessCrashManagerWait": {
+          let promises = aMessage.json.crashIds.map(crashId => {
+            return Services.crashmanager.ensureCrashIsPresent(crashId);
+          });
+          return Promise.all(promises);
+        }
+
+        case "SPPermissionManager": {
+          let msg = aMessage.data;
+          switch (msg.op) {
+            case "add":
+            case "remove":
+              this._permOp(msg);
+              break;
+            case "has":
+              let hasPerm = Services.perms.testPermissionFromPrincipal(
+                msg.principal,
+                msg.type
+              );
+              return hasPerm == Ci.nsIPermissionManager.ALLOW_ACTION;
+            case "test":
+              let testPerm = Services.perms.testPermissionFromPrincipal(
+                msg.principal,
+                msg.type
+              );
+              return testPerm == msg.value;
+            default:
+              throw new SpecialPowersError(
+                "Invalid operation for SPPermissionManager"
+              );
+          }
+          return undefined; // See comment at the beginning of this function.
+        }
+
+        case "SPObserverService": {
+          let topic = aMessage.json.observerTopic;
+          switch (aMessage.json.op) {
+            case "notify":
+              let data = aMessage.json.observerData;
+              Services.obs.notifyObservers(null, topic, data);
+              break;
+            case "add":
+              this._registerObservers._add(topic);
+              break;
+            default:
+              throw new SpecialPowersError(
+                "Invalid operation for SPObserverervice"
+              );
+          }
+          return undefined; // See comment at the beginning of this function.
+        }
+
+        case "SPLoadChromeScript": {
+          let id = aMessage.json.id;
+          let scriptName;
+
+          let jsScript = aMessage.json.function.body;
+          if (aMessage.json.url) {
+            scriptName = aMessage.json.url;
+          } else if (aMessage.json.function) {
+            scriptName =
+              aMessage.json.function.name ||
+              "<loadChromeScript anonymous function>";
+          } else {
+            throw new SpecialPowersError("SPLoadChromeScript: Invalid script");
+          }
+
+          // Setup a chrome sandbox that has access to sendAsyncMessage
+          // and {add,remove}MessageListener in order to communicate with
+          // the mochitest.
+          let sb = new lazy.SpecialPowersSandbox(
+            scriptName,
+            data => {
+              this.sendAsyncMessage("Assert", data);
+            },
+            aMessage.data
+          );
+
+          Object.assign(sb.sandbox, {
+            createWindowlessBrowser,
+            sendAsyncMessage: (name, message) => {
+              this.sendAsyncMessage("SPChromeScriptMessage", {
+                id,
+                name,
+                message,
+              });
+            },
+            addMessageListener: (name, listener) => {
+              this._chromeScriptListeners.push({ id, name, listener });
+            },
+            removeMessageListener: (name, listener) => {
+              let index = this._chromeScriptListeners.findIndex(function (obj) {
+                return (
+                  obj.id == id && obj.name == name && obj.listener == listener
+                );
+              });
+              if (index >= 0) {
+                this._chromeScriptListeners.splice(index, 1);
+              }
+            },
+            actorParent: this.manager,
+          });
+
+          // Evaluate the chrome script
+          try {
+            Cu.evalInSandbox(jsScript, sb.sandbox, "1.8", scriptName, 1);
+          } catch (e) {
+            throw new SpecialPowersError(
+              "Error while executing chrome script '" +
+                scriptName +
+                "':\n" +
+                e +
+                "\n" +
+                e.fileName +
+                ":" +
+                e.lineNumber
+            );
+          }
+          return undefined; // See comment at the beginning of this function.
+        }
+
+        case "SPChromeScriptMessage": {
+          let id = aMessage.json.id;
+          let name = aMessage.json.name;
+          let message = aMessage.json.message;
+          let result;
+          for (let listener of this._chromeScriptListeners) {
+            if (listener.name == name && listener.id == id) {
+              result = listener.listener(message);
+            }
+          }
+          return result;
+        }
+
+        case "SPCleanUpSTSData": {
+          let origin = aMessage.data.origin;
+          let uri = Services.io.newURI(origin);
+          let sss = Cc["@mozilla.org/ssservice;1"].getService(
+            Ci.nsISiteSecurityService
+          );
+          sss.resetState(uri);
+          return undefined;
+        }
+
+        case "SPRequestDumpCoverageCounters": {
+          return lazy.PerTestCoverageUtils.afterTest();
+        }
+
+        case "SPRequestResetCoverageCounters": {
+          return lazy.PerTestCoverageUtils.beforeTest();
+        }
+
+        case "SPCheckServiceWorkers": {
+          let swm = Cc["@mozilla.org/serviceworkers/manager;1"].getService(
+            Ci.nsIServiceWorkerManager
+          );
+          let regs = swm.getAllRegistrations();
+
+          // XXX This code is shared with specialpowers.js.
+          let workers = new Array(regs.length);
+          for (let i = 0; i < regs.length; ++i) {
+            let { scope, scriptSpec } = regs.queryElementAt(
+              i,
+              Ci.nsIServiceWorkerRegistrationInfo
+            );
+            workers[i] = { scope, scriptSpec };
+          }
+          return { workers };
+        }
+
+        case "SPLoadExtension": {
+          let id = aMessage.data.id;
+          let ext = aMessage.data.ext;
+          if (AppConstants.platform === "android") {
+            // Some extension APIs are partially implemented in Java, and the
+            // interface between the JS and Java side (GeckoViewWebExtension)
+            // expects extensions to be registered with the AddonManager.
+            //
+            // For simplicity, default to using an Addon Manager (if not null).
+            if (ext.useAddonManager === undefined) {
+              ext.useAddonManager = "android-only";
+            }
+          }
+          // delayedStartup is only supported in xpcshell
+          if (ext.delayedStartup !== undefined) {
+            throw new Error(
+              `delayedStartup is only supported in xpcshell, use "useAddonManager".`
+            );
+          }
+
+          let extension = lazy.ExtensionTestCommon.generate(ext);
+
+          let resultListener = (...args) => {
+            this.sendAsyncMessage("SPExtensionMessage", {
+              id,
+              type: "testResult",
+              args,
+            });
+          };
+
+          let messageListener = (...args) => {
+            args.shift();
+            this.sendAsyncMessage("SPExtensionMessage", {
+              id,
+              type: "testMessage",
+              args,
+            });
+          };
+
+          // Register pass/fail handlers.
+          extension.on("test-result", resultListener);
+          extension.on("test-eq", resultListener);
+          extension.on("test-log", resultListener);
+          extension.on("test-done", resultListener);
+
+          extension.on("test-message", messageListener);
+
+          this._extensions.set(id, extension);
+          return undefined;
+        }
+
+        case "SPStartupExtension": {
+          let id = aMessage.data.id;
+          // This is either an Extension, or (if useAddonManager is set) a MockExtension.
+          let extension = this._extensions.get(id);
+          extension.on("startup", (eventName, ext) => {
+            if (AppConstants.platform === "android") {
+              // We need a way to notify the embedding layer that a new extension
+              // has been installed, so that the java layer can be updated too.
+              Services.obs.notifyObservers(null, "testing-installed-addon", id);
+            }
+            // ext is always the "real" Extension object, even when "extension"
+            // is a MockExtension.
+            this.sendAsyncMessage("SPExtensionMessage", {
+              id,
+              type: "extensionSetId",
+              args: [ext.id, ext.uuid],
+            });
+          });
+
+          // Make sure the extension passes the packaging checks when
+          // they're run on a bare archive rather than a running instance,
+          // as the add-on manager runs them.
+          let extensionData = new lazy.ExtensionData(extension.rootURI);
+          return extensionData
+            .loadManifest()
+            .then(
+              () => {
+                return extensionData.initAllLocales().then(() => {
+                  if (extensionData.errors.length) {
+                    return Promise.reject(
+                      "Extension contains packaging errors"
+                    );
+                  }
+                  return undefined;
+                });
+              },
+              () => {
+                // loadManifest() will throw if we're loading an embedded
+                // extension, so don't worry about locale errors in that
+                // case.
+              }
+            )
+            .then(async () => {
+              // browser tests do not call startup in ExtensionXPCShellUtils or MockExtension,
+              // in that case we have an ID here and we need to set the override.
+              if (extension.id) {
+                await lazy.ExtensionTestCommon.setIncognitoOverride(extension);
+              }
+              return extension.startup().then(
+                () => {},
+                e => {
+                  dump(`Extension startup failed: ${e}\n${e.stack}`);
+                  throw e;
+                }
+              );
+            });
+        }
+
+        case "SPExtensionMessage": {
+          let id = aMessage.data.id;
+          let extension = this._extensions.get(id);
+          extension.testMessage(...aMessage.data.args);
+          return undefined;
+        }
+
+        case "SPExtensionGrantActiveTab": {
+          let { id, tabId } = aMessage.data;
+          let { tabManager } = this._extensions.get(id);
+          tabManager.addActiveTabPermission(tabManager.get(tabId).nativeTab);
+          return undefined;
+        }
+
+        case "SPUnloadExtension": {
+          let id = aMessage.data.id;
+          let extension = this._extensions.get(id);
+          this._extensions.delete(id);
+          return extension.shutdown().then(() => {
+            return extension._uninstallPromise;
+          });
+        }
+
+        case "SPExtensionTerminateBackground": {
+          let id = aMessage.data.id;
+          let args = aMessage.data.args;
+          let extension = this._extensions.get(id);
+          return extension.terminateBackground(...args);
+        }
+
+        case "SPExtensionWakeupBackground": {
+          let id = aMessage.data.id;
+          let extension = this._extensions.get(id);
+          return extension.wakeupBackground();
+        }
+
+        case "SetAsDefaultAssertHandler": {
+          defaultAssertHandler = this;
+          return undefined;
+        }
+
+        case "Spawn": {
+          // Use a different variable for the profiler marker start time
+          // so that a marker isn't added when we return, but instead when
+          // our promise resolves.
+          let spawnStartTime = startTime;
+          startTime = undefined;
+          let { browsingContext, task, args, caller, hasHarness, imports } =
+            aMessage.data;
+
+          let spParent =
+            browsingContext.currentWindowGlobal.getActor("SpecialPowers");
+
+          let taskId = nextTaskID++;
+          if (hasHarness) {
+            spParent._taskActors.set(taskId, this);
+          }
+
+          return spParent
+            .sendQuery("Spawn", { task, args, caller, taskId, imports })
+            .finally(() => {
+              ChromeUtils.addProfilerMarker(
+                "SpecialPowers",
+                { startTime: spawnStartTime, category: "Test" },
+                aMessage.name
+              );
+              return spParent._taskActors.delete(taskId);
+            });
+        }
+
+        case "SpawnChrome": {
+          let { task, args, caller, imports } = aMessage.data;
+
+          return this._spawnChrome(task, args, caller, imports);
+        }
+
+        case "Snapshot": {
+          let { browsingContext, rect, background, resetScrollPosition } =
+            aMessage.data;
+
+          return browsingContext.currentWindowGlobal
+            .drawSnapshot(rect, 1.0, background, resetScrollPosition)
+            .then(async image => {
+              let hiddenFrame = new lazy.HiddenFrame();
+              let win = await hiddenFrame.get();
+
+              let canvas = win.document.createElement("canvas");
+              canvas.width = image.width;
+              canvas.height = image.height;
+
+              const ctx = canvas.getContext("2d");
+              ctx.drawImage(image, 0, 0);
+
+              let data = ctx.getImageData(0, 0, image.width, image.height);
+              hiddenFrame.destroy();
+              return data;
+            });
+        }
+
+        case "SecurityState": {
+          let { browsingContext } = aMessage.data;
+          return browsingContext.secureBrowserUI.state;
+        }
+
+        case "ProxiedAssert": {
+          let { taskId, data } = aMessage.data;
+
+          let actor = this._taskActors.get(taskId) || defaultAssertHandler;
+          actor.sendAsyncMessage("Assert", data);
+
+          return undefined;
+        }
+
+        case "SPRemoveAllServiceWorkers": {
+          return lazy.ServiceWorkerCleanUp.removeAll();
+        }
+
+        case "SPRemoveServiceWorkerDataForExampleDomain": {
+          return lazy.ServiceWorkerCleanUp.removeFromHost("example.com");
+        }
+
+        case "SPGenerateMediaControlKeyTestEvent": {
+          // eslint-disable-next-line no-undef
+          MediaControlService.generateMediaControlKey(aMessage.data.event);
+          return undefined;
+        }
+
+        default:
+          throw new SpecialPowersError(
+            `Unrecognized Special Powers API: ${aMessage.name}`
+          );
+      }
+      // This should be unreachable. If it ever becomes reachable, ESLint
+      // will produce an error about inconsistent return values.
+    } finally {
+      if (startTime) {
+        ChromeUtils.addProfilerMarker(
+          "SpecialPowers",
+          { startTime, category: "Test" },
+          aMessage.name
+        );
+      }
+    }
+  }
+}
diff --git a/testing/specialpowers/content/SpecialPowersSandbox.sys.mjs b/testing/specialpowers/content/SpecialPowersSandbox.sys.mjs
new file mode 100644
index 0000000000..4f9e060595
--- /dev/null
+++ b/testing/specialpowers/content/SpecialPowersSandbox.sys.mjs
@@ -0,0 +1,141 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * This modules handles creating and provisioning Sandboxes for
+ * executing cross-process code from SpecialPowers. This allows all such
+ * sandboxes to have a similar environment, and in particular allows
+ * them to run test assertions in the target process and propagate
+ * results back to the caller.
+ */
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  Assert: "resource://testing-common/Assert.sys.mjs",
+});
+
+// Note: When updating the set of globals exposed to sandboxes by
+// default, please also update the ESLint plugin rule defined in
+// import-content-task-globals.js.
+const SANDBOX_GLOBALS = [
+  "Blob",
+  "ChromeUtils",
+  "FileReader",
+  "TextDecoder",
+  "TextEncoder",
+  "URL",
+];
+const EXTRA_IMPORTS = {
+  EventUtils: "resource://testing-common/SpecialPowersEventUtils.sys.mjs",
+};
+
+let expectFail = false;
+function expectingFail(fn) {
+  try {
+    expectFail = true;
+    fn();
+  } finally {
+    expectFail = false;
+  }
+}
+
+export class SpecialPowersSandbox {
+  constructor(name, reportCallback, opts = {}) {
+    this.name = name;
+    this.reportCallback = reportCallback;
+
+    this._Assert = null;
+
+    this.sandbox = Cu.Sandbox(
+      Cu.getGlobalForObject({}),
+      Object.assign(
+        { wantGlobalProperties: SANDBOX_GLOBALS },
+        opts.sandboxOptions
+      )
+    );
+
+    for (let prop of ["assert", "Assert"]) {
+      Object.defineProperty(this.sandbox, prop, {
+        get: () => {
+          return this.Assert;
+        },
+        enumerable: true,
+        configurable: true,
+      });
+    }
+
+    let imports = {
+      ...EXTRA_IMPORTS,
+      ...opts.imports,
+    };
+    // We explicitly want these directly in the sandbox, and we aren't going
+    // to be using the globals within this file.
+    // eslint-disable-next-line mozilla/lazy-getter-object-name
+    ChromeUtils.defineESModuleGetters(this.sandbox, imports);
+
+    // Note: When updating the set of globals exposed to sandboxes by
+    // default, please also update the ESLint plugin rule defined in
+    // import-content-task-globals.js.
+    Object.assign(this.sandbox, {
+      BrowsingContext,
+      InspectorUtils,
+      ok: (...args) => {
+        this.Assert.ok(...args);
+      },
+      is: (...args) => {
+        this.Assert.equal(...args);
+      },
+      isnot: (...args) => {
+        this.Assert.notEqual(...args);
+      },
+      todo: (...args) => {
+        expectingFail(() => this.Assert.ok(...args));
+      },
+      todo_is: (...args) => {
+        expectingFail(() => this.Assert.equal(...args));
+      },
+      info: info => {
+        this.reportCallback({ info });
+      },
+    });
+  }
+
+  get Assert() {
+    if (!this._Assert) {
+      this._Assert = new lazy.Assert((err, message, stack) => {
+        this.report(err, message, stack);
+      });
+    }
+    return this._Assert;
+  }
+
+  report(err, name, stack) {
+    let diag;
+    if (err) {
+      diag =
+        `got ${uneval(err.actual)}, expected ${uneval(err.expected)} ` +
+        `(operator ${err.operator})`;
+    }
+
+    this.reportCallback({
+      name,
+      diag,
+      passed: !err,
+      stack: stack && stack.formattedStack,
+      expectFail,
+    });
+  }
+
+  execute(task, args, caller) {
+    let func = Cu.evalInSandbox(
+      `(${task})`,
+      this.sandbox,
+      undefined,
+      caller.filename,
+      caller.lineNumber
+    );
+    return func(...args);
+  }
+}
diff --git a/testing/specialpowers/content/WrapPrivileged.sys.mjs b/testing/specialpowers/content/WrapPrivileged.sys.mjs
new file mode 100644
index 0000000000..5fe67a94e2
--- /dev/null
+++ b/testing/specialpowers/content/WrapPrivileged.sys.mjs
@@ -0,0 +1,385 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * This module handles wrapping privileged objects so that they can be exposed
+ * to unprivileged contexts. It is only to be used in automated tests.
+ *
+ * Its exact semantics are also liable to change at any time, so any callers
+ * relying on undocumented behavior or subtle platform features should expect
+ * breakage. Those callers should, wherever possible, migrate to fully
+ * chrome-privileged scripts when they need to interact with privileged APIs.
+ */
+
+// XPCNativeWrapper is not defined globally in ESLint as it may be going away.
+// See bug 1481337.
+/* globals XPCNativeWrapper */
+
+Cu.crashIfNotInAutomation();
+
+let wrappedObjects = new WeakMap();
+let perWindowInfo = new WeakMap();
+let noAutoWrap = new WeakSet();
+
+function isWrappable(x) {
+  if (typeof x === "object") {
+    return x !== null;
+  }
+  return typeof x === "function";
+}
+
+function isWrapper(x) {
+  try {
+    return isWrappable(x) && wrappedObjects.has(x);
+  } catch (e) {
+    // If `x` is a remote object proxy, trying to access an unexpected property
+    // on it will throw a security error, even though we're chrome privileged.
+    // However, remote proxies are not SpecialPowers wrappers, so:
+    return false;
+  }
+}
+
+function unwrapIfWrapped(x) {
+  return isWrapper(x) ? unwrapPrivileged(x) : x;
+}
+
+function wrapIfUnwrapped(x, w) {
+  return isWrapper(x) ? x : wrapPrivileged(x, w);
+}
+
+function isObjectOrArray(obj) {
+  if (Object(obj) !== obj) {
+    return false;
+  }
+  let arrayClasses = [
+    "Object",
+    "Array",
+    "Int8Array",
+    "Uint8Array",
+    "Int16Array",
+    "Uint16Array",
+    "Int32Array",
+    "Uint32Array",
+    "Float32Array",
+    "Float64Array",
+    "Uint8ClampedArray",
+  ];
+  let className = Cu.getClassName(obj, true);
+  return arrayClasses.includes(className);
+}
+
+// In general, we want Xray wrappers for content DOM objects, because waiving
+// Xray gives us Xray waiver wrappers that clamp the principal when we cross
+// compartment boundaries. However, there are some exceptions where we want
+// to use a waiver:
+//
+// * Xray adds some gunk to toString(), which has the potential to confuse
+//   consumers that aren't expecting Xray wrappers. Since toString() is a
+//   non-privileged method that returns only strings, we can just waive Xray
+//   for that case.
+//
+// * We implement Xrays to pure JS [[Object]] and [[Array]] instances that
+//   filter out tricky things like callables. This is the right thing for
+//   security in general, but tends to break tests that try to pass object
+//   literals into SpecialPowers. So we waive [[Object]] and [[Array]]
+//   instances before inspecting properties.
+//
+// * When we don't have meaningful Xray semantics, we create an Opaque
+//   XrayWrapper for security reasons. For test code, we generally want to see
+//   through that sort of thing.
+function waiveXraysIfAppropriate(obj, propName) {
+  if (
+    propName == "toString" ||
+    isObjectOrArray(obj) ||
+    /Opaque/.test(Object.prototype.toString.call(obj))
+  ) {
+    return XPCNativeWrapper.unwrap(obj);
+  }
+  return obj;
+}
+
+// We can't call apply() directy on Xray-wrapped functions, so we have to be
+// clever.
+function doApply(fun, invocant, args) {
+  // We implement Xrays to pure JS [[Object]] instances that filter out tricky
+  // things like callables. This is the right thing for security in general,
+  // but tends to break tests that try to pass object literals into
+  // SpecialPowers. So we waive [[Object]] instances when they're passed to a
+  // SpecialPowers-wrapped callable.
+  //
+  // Note that the transitive nature of Xray waivers means that any property
+  // pulled off such an object will also be waived, and so we'll get principal
+  // clamping for Xrayed DOM objects reached from literals, so passing things
+  // like {l : xoWin.location} won't work. Hopefully the rabbit hole doesn't
+  // go that deep.
+  args = args.map(x => (isObjectOrArray(x) ? Cu.waiveXrays(x) : x));
+  return Reflect.apply(fun, invocant, args);
+}
+
+function wrapPrivileged(obj, win) {
+  // Primitives pass straight through.
+  if (!isWrappable(obj)) {
+    return obj;
+  }
+
+  // No double wrapping.
+  if (isWrapper(obj)) {
+    throw new Error("Trying to double-wrap object!");
+  }
+
+  let { windowID, proxies, handler } = perWindowInfo.get(win) || {};
+  // |windowUtils| is undefined if |win| is a non-window object
+  // such as a sandbox.
+  let currentID = win.windowGlobalChild
+    ? win.windowGlobalChild.innerWindowId
+    : 0;
+  // Values are dead objects if the inner window is changed.
+  if (windowID !== currentID) {
+    windowID = currentID;
+    proxies = new WeakMap();
+    handler = Cu.cloneInto(SpecialPowersHandler, win, {
+      cloneFunctions: true,
+    });
+    handler.wrapped = new win.WeakMap();
+    perWindowInfo.set(win, { windowID, proxies, handler });
+  }
+
+  if (proxies.has(obj)) {
+    return proxies.get(obj).proxy;
+  }
+
+  let className = Cu.getClassName(obj, true);
+  if (className === "ArrayBuffer") {
+    // Since |new Uint8Array(<proxy>)| doesn't work as expected, we have to
+    // return a real ArrayBuffer.
+    return obj instanceof win.ArrayBuffer ? obj : Cu.cloneInto(obj, win);
+  }
+
+  let dummy;
+  if (typeof obj === "function") {
+    dummy = Cu.exportFunction(function () {}, win);
+  } else {
+    dummy = new win.Object();
+  }
+  handler.wrapped.set(dummy, { obj });
+
+  let proxy = new win.Proxy(dummy, handler);
+  wrappedObjects.set(proxy, obj);
+  switch (className) {
+    case "AnonymousContent":
+      // Caching anonymous content will cause crashes (bug 1636015).
+      break;
+    case "CSS2Properties":
+    case "CSSStyleRule":
+    case "CSSStyleSheet":
+      // Caching these classes will cause memory leaks.
+      break;
+    default:
+      proxies.set(obj, { proxy });
+      break;
+  }
+  return proxy;
+}
+
+function unwrapPrivileged(x) {
+  // We don't wrap primitives, so sometimes we have a primitive where we'd
+  // expect to have a wrapper. The proxy pretends to be the type that it's
+  // emulating, so we can just as easily check isWrappable() on a proxy as
+  // we can on an unwrapped object.
+  if (!isWrappable(x)) {
+    return x;
+  }
+
+  // If we have a wrappable type, make sure it's wrapped.
+  if (!isWrapper(x)) {
+    throw new Error("Trying to unwrap a non-wrapped object!");
+  }
+
+  // unwrapped.
+  return wrappedObjects.get(x);
+}
+
+function wrapExceptions(global, fn) {
+  try {
+    return fn();
+  } catch (e) {
+    throw wrapIfUnwrapped(e, global);
+  }
+}
+
+let SpecialPowersHandler = {
+  construct(target, args) {
+    // The arguments may or may not be wrappers. Unwrap them if necessary.
+    var unwrappedArgs = Array.from(Cu.waiveXrays(args), x =>
+      unwrapIfWrapped(Cu.unwaiveXrays(x))
+    );
+
+    // We want to invoke "obj" as a constructor, but using unwrappedArgs as
+    // the arguments.
+    let global = Cu.getGlobalForObject(this);
+    return wrapExceptions(global, () =>
+      wrapIfUnwrapped(
+        Reflect.construct(this.wrapped.get(target).obj, unwrappedArgs),
+        global
+      )
+    );
+  },
+
+  apply(target, thisValue, args) {
+    let wrappedObject = this.wrapped.get(target).obj;
+    let global = Cu.getGlobalForObject(this);
+    // The invocant and arguments may or may not be wrappers. Unwrap
+    // them if necessary.
+    var invocant = unwrapIfWrapped(thisValue);
+
+    return wrapExceptions(global, () => {
+      if (noAutoWrap.has(wrappedObject)) {
+        args = Array.from(Cu.waiveXrays(args), x => Cu.unwaiveXrays(x));
+        return doApply(wrappedObject, invocant, args);
+      }
+
+      if (wrappedObject.name == "then") {
+        args = Array.from(Cu.waiveXrays(args), x =>
+          wrapCallback(Cu.unwaiveXrays(x), global)
+        );
+      } else {
+        args = Array.from(Cu.waiveXrays(args), x =>
+          unwrapIfWrapped(Cu.unwaiveXrays(x))
+        );
+      }
+
+      return wrapIfUnwrapped(doApply(wrappedObject, invocant, args), global);
+    });
+  },
+
+  has(target, prop) {
+    return Reflect.has(this.wrapped.get(target).obj, prop);
+  },
+
+  get(target, prop, receiver) {
+    let global = Cu.getGlobalForObject(this);
+    return wrapExceptions(global, () => {
+      let obj = waiveXraysIfAppropriate(this.wrapped.get(target).obj, prop);
+      let val = Reflect.get(obj, prop);
+      return wrapIfUnwrapped(val, global);
+    });
+  },
+
+  set(target, prop, val, receiver) {
+    return wrapExceptions(Cu.getGlobalForObject(this), () => {
+      let obj = waiveXraysIfAppropriate(this.wrapped.get(target).obj, prop);
+      return Reflect.set(obj, prop, unwrapIfWrapped(val));
+    });
+  },
+
+  delete(target, prop) {
+    return wrapExceptions(Cu.getGlobalForObject(this), () => {
+      return Reflect.deleteProperty(this.wrapped.get(target).obj, prop);
+    });
+  },
+
+  defineProperty(target, prop, descriptor) {
+    throw new Error(
+      "Can't call defineProperty on SpecialPowers wrapped object"
+    );
+  },
+
+  getOwnPropertyDescriptor(target, prop) {
+    let global = Cu.getGlobalForObject(this);
+    return wrapExceptions(global, () => {
+      let obj = waiveXraysIfAppropriate(this.wrapped.get(target).obj, prop);
+      let desc = Reflect.getOwnPropertyDescriptor(obj, prop);
+
+      if (desc === undefined) {
+        return undefined;
+      }
+
+      // Transitively maintain the wrapper membrane.
+      let wrapIfExists = key => {
+        if (key in desc) {
+          desc[key] = wrapIfUnwrapped(desc[key], global);
+        }
+      };
+
+      wrapIfExists("value");
+      wrapIfExists("get");
+      wrapIfExists("set");
+
+      // A trapping proxy's properties must always be configurable, but sometimes
+      // we come across non-configurable properties. Tell a white lie.
+      desc.configurable = true;
+
+      return wrapIfUnwrapped(desc, global);
+    });
+  },
+
+  ownKeys(target) {
+    let props = [];
+
+    // Do the normal thing.
+    let wrappedObject = this.wrapped.get(target).obj;
+    let flt = a => !props.includes(a);
+    props = props.concat(Reflect.ownKeys(wrappedObject).filter(flt));
+
+    // If we've got an Xray wrapper, include the expandos as well.
+    if ("wrappedJSObject" in wrappedObject) {
+      props = props.concat(
+        Reflect.ownKeys(wrappedObject.wrappedJSObject).filter(flt)
+      );
+    }
+
+    return Cu.cloneInto(props, Cu.getGlobalForObject(this));
+  },
+
+  preventExtensions(target) {
+    throw new Error(
+      "Can't call preventExtensions on SpecialPowers wrapped object"
+    );
+  },
+};
+
+function wrapCallback(cb, win) {
+  // Do not wrap if it is already privileged.
+  if (!isWrappable(cb) || Cu.getObjectPrincipal(cb).isSystemPrincipal) {
+    return cb;
+  }
+  return function SpecialPowersCallbackWrapper() {
+    var args = Array.from(arguments, obj => wrapIfUnwrapped(obj, win));
+    let invocant = wrapIfUnwrapped(this, win);
+    return unwrapIfWrapped(cb.apply(invocant, args));
+  };
+}
+
+function wrapCallbackObject(obj, win) {
+  // Do not wrap if it is already privileged.
+  if (!isWrappable(obj) || Cu.getObjectPrincipal(obj).isSystemPrincipal) {
+    return obj;
+  }
+  obj = Cu.waiveXrays(obj);
+  var wrapper = {};
+  for (var i in obj) {
+    if (typeof obj[i] == "function") {
+      wrapper[i] = wrapCallback(Cu.unwaiveXrays(obj[i]), win);
+    } else {
+      wrapper[i] = obj[i];
+    }
+  }
+  return wrapper;
+}
+
+function disableAutoWrap(...objs) {
+  objs.forEach(x => noAutoWrap.add(x));
+}
+
+export var WrapPrivileged = {
+  wrap: wrapIfUnwrapped,
+  unwrap: unwrapIfWrapped,
+
+  isWrapper,
+
+  wrapCallback,
+  wrapCallbackObject,
+
+  disableAutoWrap,
+};
diff --git a/testing/specialpowers/manifest.json b/testing/specialpowers/manifest.json
new file mode 100644
index 0000000000..c0ffce0005
--- /dev/null
+++ b/testing/specialpowers/manifest.json
@@ -0,0 +1,23 @@
+{
+  "manifest_version": 2,
+  "name": "Special Powers",
+  "version": "2018.6.27",
+
+  "browser_specific_settings": {
+    "gecko": {
+      "id": "special-powers@mozilla.org"
+    }
+  },
+  "permissions": [],
+
+  "experiment_apis": {
+    "specialpowers": {
+      "schema": "schema.json",
+      "parent": {
+        "scopes": ["addon_parent"],
+        "script": "api.js",
+        "events": ["startup"]
+      }
+    }
+  }
+}
diff --git a/testing/specialpowers/moz.build b/testing/specialpowers/moz.build
new file mode 100644
index 0000000000..7a2413e2a2
--- /dev/null
+++ b/testing/specialpowers/moz.build
@@ -0,0 +1,40 @@
+# -*- 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/.
+
+XPI_NAME = "specialpowers"
+
+USE_EXTENSION_MANIFEST = True
+
+FINAL_TARGET_FILES += [
+    "api.js",
+    "manifest.json",
+    "schema.json",
+]
+
+FINAL_TARGET_FILES.content += [
+    "content/AppTestDelegate.sys.mjs",
+    "content/AppTestDelegateChild.sys.mjs",
+    "content/AppTestDelegateParent.sys.mjs",
+]
+
+modules = [
+    "content/ContentTaskUtils.sys.mjs",
+    "content/MockColorPicker.sys.mjs",
+    "content/MockFilePicker.sys.mjs",
+    "content/MockPermissionPrompt.sys.mjs",
+    "content/SpecialPowersChild.sys.mjs",
+    "content/SpecialPowersEventUtils.sys.mjs",
+    "content/SpecialPowersParent.sys.mjs",
+    "content/SpecialPowersSandbox.sys.mjs",
+    "content/WrapPrivileged.sys.mjs",
+]
+
+TESTING_JS_MODULES += modules
+
+FINAL_TARGET_FILES.modules += modules
+
+with Files("**"):
+    BUG_COMPONENT = ("Testing", "Mochitest")
diff --git a/testing/specialpowers/schema.json b/testing/specialpowers/schema.json
new file mode 100644
index 0000000000..fe51488c70
--- /dev/null
+++ b/testing/specialpowers/schema.json
@@ -0,0 +1 @@
+[]