Adding upstream version 115.7.0esr.upstream/115.7.0esr

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

25 files changed, 11283 insertions, 0 deletions

diff --git a/browser/components/extensions/parent/.eslintrc.js b/browser/components/extensions/parent/.eslintrc.js
new file mode 100644
index 0000000000..1efdd83ff4
--- /dev/null
+++ b/browser/components/extensions/parent/.eslintrc.js
@@ -0,0 +1,33 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+module.exports = {
+  extends: "../../../../toolkit/components/extensions/parent/.eslintrc.js",
+
+  globals: {
+    Tab: true,
+    TabContext: true,
+    Window: true,
+    actionContextMenu: true,
+    browserActionFor: true,
+    clickModifiersFromEvent: true,
+    getContainerForCookieStoreId: true,
+    getTargetTabIdForToolbox: true,
+    getToolboxEvalOptions: true,
+    isContainerCookieStoreId: true,
+    isPrivateCookieStoreId: true,
+    isValidCookieStoreId: true,
+    makeWidgetId: true,
+    openOptionsPage: true,
+    pageActionFor: true,
+    replaceUrlInTab: true,
+    searchInitialized: true,
+    sidebarActionFor: true,
+    tabTracker: true,
+    waitForTabLoaded: true,
+    windowTracker: true,
+  },
+};
diff --git a/browser/components/extensions/parent/ext-bookmarks.js b/browser/components/extensions/parent/ext-bookmarks.js
new file mode 100644
index 0000000000..6dbb41dc17
--- /dev/null
+++ b/browser/components/extensions/parent/ext-bookmarks.js
@@ -0,0 +1,515 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var { XPCOMUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/XPCOMUtils.sys.mjs"
+);
+
+ChromeUtils.defineESModuleGetters(this, {
+  PlacesUtils: "resource://gre/modules/PlacesUtils.sys.mjs",
+});
+
+var { ExtensionError } = ExtensionUtils;
+
+const { TYPE_BOOKMARK, TYPE_FOLDER, TYPE_SEPARATOR } = PlacesUtils.bookmarks;
+
+const BOOKMARKS_TYPES_TO_API_TYPES_MAP = new Map([
+  [TYPE_BOOKMARK, "bookmark"],
+  [TYPE_FOLDER, "folder"],
+  [TYPE_SEPARATOR, "separator"],
+]);
+
+const BOOKMARK_SEPERATOR_URL = "data:";
+
+XPCOMUtils.defineLazyGetter(this, "API_TYPES_TO_BOOKMARKS_TYPES_MAP", () => {
+  let theMap = new Map();
+
+  for (let [code, name] of BOOKMARKS_TYPES_TO_API_TYPES_MAP) {
+    theMap.set(name, code);
+  }
+  return theMap;
+});
+
+let listenerCount = 0;
+
+function getUrl(type, url) {
+  switch (type) {
+    case TYPE_BOOKMARK:
+      return url;
+    case TYPE_SEPARATOR:
+      return BOOKMARK_SEPERATOR_URL;
+    default:
+      return undefined;
+  }
+}
+
+const getTree = (rootGuid, onlyChildren) => {
+  function convert(node, parent) {
+    let treenode = {
+      id: node.guid,
+      title: PlacesUtils.bookmarks.getLocalizedTitle(node) || "",
+      index: node.index,
+      dateAdded: node.dateAdded / 1000,
+      type: BOOKMARKS_TYPES_TO_API_TYPES_MAP.get(node.typeCode),
+      url: getUrl(node.typeCode, node.uri),
+    };
+
+    if (parent && node.guid != PlacesUtils.bookmarks.rootGuid) {
+      treenode.parentId = parent.guid;
+    }
+
+    if (node.typeCode == TYPE_FOLDER) {
+      treenode.dateGroupModified = node.lastModified / 1000;
+
+      if (!onlyChildren) {
+        treenode.children = node.children
+          ? node.children.map(child => convert(child, node))
+          : [];
+      }
+    }
+
+    return treenode;
+  }
+
+  return PlacesUtils.promiseBookmarksTree(rootGuid)
+    .then(root => {
+      if (onlyChildren) {
+        let children = root.children || [];
+        return children.map(child => convert(child, root));
+      }
+      let treenode = convert(root, null);
+      treenode.parentId = root.parentGuid;
+      // It seems like the array always just contains the root node.
+      return [treenode];
+    })
+    .catch(e => Promise.reject({ message: e.message }));
+};
+
+const convertBookmarks = result => {
+  let node = {
+    id: result.guid,
+    title: PlacesUtils.bookmarks.getLocalizedTitle(result) || "",
+    index: result.index,
+    dateAdded: result.dateAdded.getTime(),
+    type: BOOKMARKS_TYPES_TO_API_TYPES_MAP.get(result.type),
+    url: getUrl(result.type, result.url && result.url.href),
+  };
+
+  if (result.guid != PlacesUtils.bookmarks.rootGuid) {
+    node.parentId = result.parentGuid;
+  }
+
+  if (result.type == TYPE_FOLDER) {
+    node.dateGroupModified = result.lastModified.getTime();
+  }
+
+  return node;
+};
+
+const throwIfRootId = id => {
+  if (id == PlacesUtils.bookmarks.rootGuid) {
+    throw new ExtensionError("The bookmark root cannot be modified");
+  }
+};
+
+let observer = new (class extends EventEmitter {
+  constructor() {
+    super();
+    this.handlePlacesEvents = this.handlePlacesEvents.bind(this);
+  }
+
+  handlePlacesEvents(events) {
+    for (let event of events) {
+      switch (event.type) {
+        case "bookmark-added":
+          if (event.isTagging) {
+            continue;
+          }
+          let bookmark = {
+            id: event.guid,
+            parentId: event.parentGuid,
+            index: event.index,
+            title: event.title,
+            dateAdded: event.dateAdded,
+            type: BOOKMARKS_TYPES_TO_API_TYPES_MAP.get(event.itemType),
+            url: getUrl(event.itemType, event.url),
+          };
+
+          if (event.itemType == TYPE_FOLDER) {
+            bookmark.dateGroupModified = bookmark.dateAdded;
+          }
+
+          this.emit("created", bookmark);
+          break;
+        case "bookmark-removed":
+          if (event.isTagging || event.isDescendantRemoval) {
+            continue;
+          }
+          let node = {
+            id: event.guid,
+            parentId: event.parentGuid,
+            index: event.index,
+            type: BOOKMARKS_TYPES_TO_API_TYPES_MAP.get(event.itemType),
+            url: getUrl(event.itemType, event.url),
+            title: event.title,
+          };
+
+          this.emit("removed", {
+            guid: event.guid,
+            info: { parentId: event.parentGuid, index: event.index, node },
+          });
+          break;
+        case "bookmark-moved":
+          this.emit("moved", {
+            guid: event.guid,
+            info: {
+              parentId: event.parentGuid,
+              index: event.index,
+              oldParentId: event.oldParentGuid,
+              oldIndex: event.oldIndex,
+            },
+          });
+          break;
+        case "bookmark-title-changed":
+          if (event.isTagging) {
+            continue;
+          }
+
+          this.emit("changed", {
+            guid: event.guid,
+            info: { title: event.title },
+          });
+          break;
+        case "bookmark-url-changed":
+          if (event.isTagging) {
+            continue;
+          }
+
+          this.emit("changed", {
+            guid: event.guid,
+            info: { url: event.url },
+          });
+          break;
+      }
+    }
+  }
+})();
+
+const decrementListeners = () => {
+  listenerCount -= 1;
+  if (!listenerCount) {
+    PlacesUtils.observers.removeListener(
+      [
+        "bookmark-added",
+        "bookmark-removed",
+        "bookmark-moved",
+        "bookmark-title-changed",
+        "bookmark-url-changed",
+      ],
+      observer.handlePlacesEvents
+    );
+  }
+};
+
+const incrementListeners = () => {
+  listenerCount++;
+  if (listenerCount == 1) {
+    PlacesUtils.observers.addListener(
+      [
+        "bookmark-added",
+        "bookmark-removed",
+        "bookmark-moved",
+        "bookmark-title-changed",
+        "bookmark-url-changed",
+      ],
+      observer.handlePlacesEvents
+    );
+  }
+};
+
+this.bookmarks = class extends ExtensionAPIPersistent {
+  PERSISTENT_EVENTS = {
+    onCreated({ fire }) {
+      let listener = (event, bookmark) => {
+        fire.sync(bookmark.id, bookmark);
+      };
+
+      observer.on("created", listener);
+      incrementListeners();
+      return {
+        unregister() {
+          observer.off("created", listener);
+          decrementListeners();
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+
+    onRemoved({ fire }) {
+      let listener = (event, data) => {
+        fire.sync(data.guid, data.info);
+      };
+
+      observer.on("removed", listener);
+      incrementListeners();
+      return {
+        unregister() {
+          observer.off("removed", listener);
+          decrementListeners();
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+
+    onChanged({ fire }) {
+      let listener = (event, data) => {
+        fire.sync(data.guid, data.info);
+      };
+
+      observer.on("changed", listener);
+      incrementListeners();
+      return {
+        unregister() {
+          observer.off("changed", listener);
+          decrementListeners();
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+
+    onMoved({ fire }) {
+      let listener = (event, data) => {
+        fire.sync(data.guid, data.info);
+      };
+
+      observer.on("moved", listener);
+      incrementListeners();
+      return {
+        unregister() {
+          observer.off("moved", listener);
+          decrementListeners();
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+  };
+
+  getAPI(context) {
+    return {
+      bookmarks: {
+        async get(idOrIdList) {
+          let list = Array.isArray(idOrIdList) ? idOrIdList : [idOrIdList];
+
+          try {
+            let bookmarks = [];
+            for (let id of list) {
+              let bookmark = await PlacesUtils.bookmarks.fetch({ guid: id });
+              if (!bookmark) {
+                throw new Error("Bookmark not found");
+              }
+              bookmarks.push(convertBookmarks(bookmark));
+            }
+            return bookmarks;
+          } catch (error) {
+            return Promise.reject({ message: error.message });
+          }
+        },
+
+        getChildren: function (id) {
+          // TODO: We should optimize this.
+          return getTree(id, true);
+        },
+
+        getTree: function () {
+          return getTree(PlacesUtils.bookmarks.rootGuid, false);
+        },
+
+        getSubTree: function (id) {
+          return getTree(id, false);
+        },
+
+        search: function (query) {
+          return PlacesUtils.bookmarks
+            .search(query)
+            .then(result => result.map(convertBookmarks));
+        },
+
+        getRecent: function (numberOfItems) {
+          return PlacesUtils.bookmarks
+            .getRecent(numberOfItems)
+            .then(result => result.map(convertBookmarks));
+        },
+
+        create: function (bookmark) {
+          let info = {
+            title: bookmark.title || "",
+          };
+
+          info.type = API_TYPES_TO_BOOKMARKS_TYPES_MAP.get(bookmark.type);
+          if (!info.type) {
+            // If url is NULL or missing, it will be a folder.
+            if (bookmark.url !== null) {
+              info.type = TYPE_BOOKMARK;
+            } else {
+              info.type = TYPE_FOLDER;
+            }
+          }
+
+          if (info.type === TYPE_BOOKMARK) {
+            info.url = bookmark.url || "";
+          }
+
+          if (bookmark.index !== null) {
+            info.index = bookmark.index;
+          }
+
+          if (bookmark.parentId !== null) {
+            throwIfRootId(bookmark.parentId);
+            info.parentGuid = bookmark.parentId;
+          } else {
+            info.parentGuid = PlacesUtils.bookmarks.unfiledGuid;
+          }
+
+          try {
+            return PlacesUtils.bookmarks
+              .insert(info)
+              .then(convertBookmarks)
+              .catch(error => Promise.reject({ message: error.message }));
+          } catch (e) {
+            return Promise.reject({
+              message: `Invalid bookmark: ${JSON.stringify(info)}`,
+            });
+          }
+        },
+
+        move: function (id, destination) {
+          throwIfRootId(id);
+          let info = {
+            guid: id,
+          };
+
+          if (destination.parentId !== null) {
+            throwIfRootId(destination.parentId);
+            info.parentGuid = destination.parentId;
+          }
+          info.index =
+            destination.index === null
+              ? PlacesUtils.bookmarks.DEFAULT_INDEX
+              : destination.index;
+
+          try {
+            return PlacesUtils.bookmarks
+              .update(info)
+              .then(convertBookmarks)
+              .catch(error => Promise.reject({ message: error.message }));
+          } catch (e) {
+            return Promise.reject({
+              message: `Invalid bookmark: ${JSON.stringify(info)}`,
+            });
+          }
+        },
+
+        update: function (id, changes) {
+          throwIfRootId(id);
+          let info = {
+            guid: id,
+          };
+
+          if (changes.title !== null) {
+            info.title = changes.title;
+          }
+          if (changes.url !== null) {
+            info.url = changes.url;
+          }
+
+          try {
+            return PlacesUtils.bookmarks
+              .update(info)
+              .then(convertBookmarks)
+              .catch(error => Promise.reject({ message: error.message }));
+          } catch (e) {
+            return Promise.reject({
+              message: `Invalid bookmark: ${JSON.stringify(info)}`,
+            });
+          }
+        },
+
+        remove: function (id) {
+          throwIfRootId(id);
+          let info = {
+            guid: id,
+          };
+
+          // The API doesn't give you the old bookmark at the moment
+          try {
+            return PlacesUtils.bookmarks
+              .remove(info, { preventRemovalOfNonEmptyFolders: true })
+              .catch(error => Promise.reject({ message: error.message }));
+          } catch (e) {
+            return Promise.reject({
+              message: `Invalid bookmark: ${JSON.stringify(info)}`,
+            });
+          }
+        },
+
+        removeTree: function (id) {
+          throwIfRootId(id);
+          let info = {
+            guid: id,
+          };
+
+          try {
+            return PlacesUtils.bookmarks
+              .remove(info)
+              .catch(error => Promise.reject({ message: error.message }));
+          } catch (e) {
+            return Promise.reject({
+              message: `Invalid bookmark: ${JSON.stringify(info)}`,
+            });
+          }
+        },
+
+        onCreated: new EventManager({
+          context,
+          module: "bookmarks",
+          event: "onCreated",
+          extensionApi: this,
+        }).api(),
+
+        onRemoved: new EventManager({
+          context,
+          module: "bookmarks",
+          event: "onRemoved",
+          extensionApi: this,
+        }).api(),
+
+        onChanged: new EventManager({
+          context,
+          module: "bookmarks",
+          event: "onChanged",
+          extensionApi: this,
+        }).api(),
+
+        onMoved: new EventManager({
+          context,
+          module: "bookmarks",
+          event: "onMoved",
+          extensionApi: this,
+        }).api(),
+      },
+    };
+  }
+};
diff --git a/browser/components/extensions/parent/ext-browser.js b/browser/components/extensions/parent/ext-browser.js
new file mode 100644
index 0000000000..3b8a179c8d
--- /dev/null
+++ b/browser/components/extensions/parent/ext-browser.js
@@ -0,0 +1,1258 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+// This file provides some useful code for the |tabs| and |windows|
+// modules. All of the code is installed on |global|, which is a scope
+// shared among the different ext-*.js scripts.
+
+ChromeUtils.defineESModuleGetters(this, {
+  AboutReaderParent: "resource:///actors/AboutReaderParent.sys.mjs",
+  PrivateBrowsingUtils: "resource://gre/modules/PrivateBrowsingUtils.sys.mjs",
+  PromiseUtils: "resource://gre/modules/PromiseUtils.sys.mjs",
+});
+ChromeUtils.defineModuleGetter(
+  this,
+  "BrowserWindowTracker",
+  "resource:///modules/BrowserWindowTracker.jsm"
+);
+
+var { ExtensionError } = ExtensionUtils;
+
+var { defineLazyGetter } = ExtensionCommon;
+
+const READER_MODE_PREFIX = "about:reader";
+
+let tabTracker;
+let windowTracker;
+
+function isPrivateTab(nativeTab) {
+  return PrivateBrowsingUtils.isBrowserPrivate(nativeTab.linkedBrowser);
+}
+
+/* eslint-disable mozilla/balanced-listeners */
+extensions.on("uninstalling", (msg, extension) => {
+  if (extension.uninstallURL) {
+    let browser = windowTracker.topWindow.gBrowser;
+    browser.addTab(extension.uninstallURL, {
+      relatedToCurrent: true,
+      triggeringPrincipal: Services.scriptSecurityManager.createNullPrincipal(
+        {}
+      ),
+    });
+  }
+});
+
+extensions.on("page-shutdown", (type, context) => {
+  if (context.viewType == "tab") {
+    if (context.extension.id !== context.xulBrowser.contentPrincipal.addonId) {
+      // Only close extension tabs.
+      // This check prevents about:addons from closing when it contains a
+      // WebExtension as an embedded inline options page.
+      return;
+    }
+    let { gBrowser } = context.xulBrowser.ownerGlobal;
+    if (gBrowser && gBrowser.getTabForBrowser) {
+      let nativeTab = gBrowser.getTabForBrowser(context.xulBrowser);
+      if (nativeTab) {
+        gBrowser.removeTab(nativeTab);
+      }
+    }
+  }
+});
+/* eslint-enable mozilla/balanced-listeners */
+
+global.openOptionsPage = extension => {
+  let window = windowTracker.topWindow;
+  if (!window) {
+    return Promise.reject({ message: "No browser window available" });
+  }
+
+  if (extension.manifest.options_ui.open_in_tab) {
+    window.switchToTabHavingURI(extension.manifest.options_ui.page, true, {
+      triggeringPrincipal: extension.principal,
+    });
+    return Promise.resolve();
+  }
+
+  let viewId = `addons://detail/${encodeURIComponent(
+    extension.id
+  )}/preferences`;
+
+  return window.BrowserOpenAddonsMgr(viewId);
+};
+
+global.makeWidgetId = id => {
+  id = id.toLowerCase();
+  // FIXME: This allows for collisions.
+  return id.replace(/[^a-z0-9_-]/g, "_");
+};
+
+global.clickModifiersFromEvent = event => {
+  const map = {
+    shiftKey: "Shift",
+    altKey: "Alt",
+    metaKey: "Command",
+    ctrlKey: "Ctrl",
+  };
+  let modifiers = Object.keys(map)
+    .filter(key => event[key])
+    .map(key => map[key]);
+
+  if (event.ctrlKey && AppConstants.platform === "macosx") {
+    modifiers.push("MacCtrl");
+  }
+
+  return modifiers;
+};
+
+global.waitForTabLoaded = (tab, url) => {
+  return new Promise(resolve => {
+    windowTracker.addListener("progress", {
+      onLocationChange(browser, webProgress, request, locationURI, flags) {
+        if (
+          webProgress.isTopLevel &&
+          browser.ownerGlobal.gBrowser.getTabForBrowser(browser) == tab &&
+          (!url || locationURI.spec == url)
+        ) {
+          windowTracker.removeListener("progress", this);
+          resolve();
+        }
+      },
+    });
+  });
+};
+
+global.replaceUrlInTab = (gBrowser, tab, uri) => {
+  let loaded = waitForTabLoaded(tab, uri.spec);
+  gBrowser.loadURI(uri, {
+    flags: Ci.nsIWebNavigation.LOAD_FLAGS_REPLACE_HISTORY,
+    triggeringPrincipal: Services.scriptSecurityManager.getSystemPrincipal(), // This is safe from this functions usage however it would be preferred not to dot his.
+  });
+  return loaded;
+};
+
+/**
+ * Manages tab-specific and window-specific context data, and dispatches
+ * tab select events across all windows.
+ */
+global.TabContext = class extends EventEmitter {
+  /**
+   * @param {Function} getDefaultPrototype
+   *        Provides the prototype of the context value for a tab or window when there is none.
+   *        Called with a XULElement or ChromeWindow argument.
+   *        Should return an object or null.
+   */
+  constructor(getDefaultPrototype) {
+    super();
+
+    this.getDefaultPrototype = getDefaultPrototype;
+
+    this.tabData = new WeakMap();
+
+    windowTracker.addListener("progress", this);
+    windowTracker.addListener("TabSelect", this);
+
+    this.tabAdopted = this.tabAdopted.bind(this);
+    tabTracker.on("tab-adopted", this.tabAdopted);
+  }
+
+  /**
+   * Returns the context data associated with `keyObject`.
+   *
+   * @param {XULElement|ChromeWindow} keyObject
+   *        Browser tab or browser chrome window.
+   * @returns {object}
+   */
+  get(keyObject) {
+    if (!this.tabData.has(keyObject)) {
+      let data = Object.create(this.getDefaultPrototype(keyObject));
+      this.tabData.set(keyObject, data);
+    }
+
+    return this.tabData.get(keyObject);
+  }
+
+  /**
+   * Clears the context data associated with `keyObject`.
+   *
+   * @param {XULElement|ChromeWindow} keyObject
+   *        Browser tab or browser chrome window.
+   */
+  clear(keyObject) {
+    this.tabData.delete(keyObject);
+  }
+
+  handleEvent(event) {
+    if (event.type == "TabSelect") {
+      let nativeTab = event.target;
+      this.emit("tab-select", nativeTab);
+      this.emit("location-change", nativeTab);
+    }
+  }
+
+  onLocationChange(browser, webProgress, request, locationURI, flags) {
+    if (!webProgress.isTopLevel) {
+      // Only pageAction and browserAction are consuming the "location-change" event
+      // to update their per-tab status, and they should only do so in response of
+      // location changes related to the top level frame (See Bug 1493470 for a rationale).
+      return;
+    }
+    let gBrowser = browser.ownerGlobal.gBrowser;
+    let tab = gBrowser.getTabForBrowser(browser);
+    // fromBrowse will be false in case of e.g. a hash change or history.pushState
+    let fromBrowse = !(
+      flags & Ci.nsIWebProgressListener.LOCATION_CHANGE_SAME_DOCUMENT
+    );
+    this.emit("location-change", tab, fromBrowse);
+  }
+
+  /**
+   * Persists context data when a tab is moved between windows.
+   *
+   * @param {string} eventType
+   *        Event type, should be "tab-adopted".
+   * @param {NativeTab} adoptingTab
+   *        The tab which is being opened and adopting `adoptedTab`.
+   * @param {NativeTab} adoptedTab
+   *        The tab which is being closed and adopted by `adoptingTab`.
+   */
+  tabAdopted(eventType, adoptingTab, adoptedTab) {
+    if (!this.tabData.has(adoptedTab)) {
+      return;
+    }
+    // Create a new object (possibly with different inheritance) when a tab is moved
+    // into a new window. But then reassign own properties from the old object.
+    let newData = this.get(adoptingTab);
+    let oldData = this.tabData.get(adoptedTab);
+    this.tabData.delete(adoptedTab);
+    Object.assign(newData, oldData);
+  }
+
+  /**
+   * Makes the TabContext instance stop emitting events.
+   */
+  shutdown() {
+    windowTracker.removeListener("progress", this);
+    windowTracker.removeListener("TabSelect", this);
+    tabTracker.off("tab-adopted", this.tabAdopted);
+  }
+};
+
+// This promise is used to wait for the search service to be initialized.
+// None of the code in the WebExtension modules requests that initialization.
+// It is assumed that it is started at some point. That might never happen,
+// e.g. if the application shuts down before the search service initializes.
+XPCOMUtils.defineLazyGetter(global, "searchInitialized", () => {
+  if (Services.search.isInitialized) {
+    return Promise.resolve();
+  }
+  return ExtensionUtils.promiseObserved(
+    "browser-search-service",
+    (_, data) => data == "init-complete"
+  );
+});
+
+class WindowTracker extends WindowTrackerBase {
+  addProgressListener(window, listener) {
+    window.gBrowser.addTabsProgressListener(listener);
+  }
+
+  removeProgressListener(window, listener) {
+    window.gBrowser.removeTabsProgressListener(listener);
+  }
+
+  /**
+   * @param {BaseContext} context
+   *        The extension context
+   * @returns {DOMWindow|null} topNormalWindow
+   *        The currently active, or topmost, browser window, or null if no
+   *        browser window is currently open.
+   *        Will return the topmost "normal" (i.e., not popup) window.
+   */
+  getTopNormalWindow(context) {
+    let options = { allowPopups: false };
+    if (!context.privateBrowsingAllowed) {
+      options.private = false;
+    }
+    return BrowserWindowTracker.getTopWindow(options);
+  }
+}
+
+class TabTracker extends TabTrackerBase {
+  constructor() {
+    super();
+
+    this._tabs = new WeakMap();
+    this._browsers = new WeakMap();
+    this._tabIds = new Map();
+    this._nextId = 1;
+    this._deferredTabOpenEvents = new WeakMap();
+
+    this._handleTabDestroyed = this._handleTabDestroyed.bind(this);
+  }
+
+  init() {
+    if (this.initialized) {
+      return;
+    }
+    this.initialized = true;
+
+    this.adoptedTabs = new WeakSet();
+
+    this._handleWindowOpen = this._handleWindowOpen.bind(this);
+    this._handleWindowClose = this._handleWindowClose.bind(this);
+
+    windowTracker.addListener("TabClose", this);
+    windowTracker.addListener("TabOpen", this);
+    windowTracker.addListener("TabSelect", this);
+    windowTracker.addListener("TabMultiSelect", this);
+    windowTracker.addOpenListener(this._handleWindowOpen);
+    windowTracker.addCloseListener(this._handleWindowClose);
+
+    AboutReaderParent.addMessageListener("Reader:UpdateReaderButton", this);
+
+    /* eslint-disable mozilla/balanced-listeners */
+    this.on("tab-detached", this._handleTabDestroyed);
+    this.on("tab-removed", this._handleTabDestroyed);
+    /* eslint-enable mozilla/balanced-listeners */
+  }
+
+  getId(nativeTab) {
+    let id = this._tabs.get(nativeTab);
+    if (id) {
+      return id;
+    }
+
+    this.init();
+
+    id = this._nextId++;
+    this.setId(nativeTab, id);
+    return id;
+  }
+
+  getBrowserTabId(browser) {
+    let id = this._browsers.get(browser);
+    if (id) {
+      return id;
+    }
+
+    let tab = browser.ownerGlobal.gBrowser.getTabForBrowser(browser);
+    if (tab) {
+      id = this.getId(tab);
+      this._browsers.set(browser, id);
+      return id;
+    }
+    return -1;
+  }
+
+  setId(nativeTab, id) {
+    if (!nativeTab.parentNode) {
+      throw new Error("Cannot attach ID to a destroyed tab.");
+    }
+    if (nativeTab.ownerGlobal.closed) {
+      throw new Error("Cannot attach ID to a tab in a closed window.");
+    }
+
+    this._tabs.set(nativeTab, id);
+    if (nativeTab.linkedBrowser) {
+      this._browsers.set(nativeTab.linkedBrowser, id);
+    }
+    this._tabIds.set(id, nativeTab);
+  }
+
+  /**
+   * Handles tab adoption when a tab is moved between windows.
+   * Ensures the new tab will have the same ID as the old one, and
+   * emits "tab-adopted", "tab-detached" and "tab-attached" events.
+   *
+   * @param {NativeTab} adoptingTab
+   *        The tab which is being opened and adopting `adoptedTab`.
+   * @param {NativeTab} adoptedTab
+   *        The tab which is being closed and adopted by `adoptingTab`.
+   */
+  adopt(adoptingTab, adoptedTab) {
+    if (this.adoptedTabs.has(adoptedTab)) {
+      // The adoption has already been handled.
+      return;
+    }
+    this.adoptedTabs.add(adoptedTab);
+    let tabId = this.getId(adoptedTab);
+    this.setId(adoptingTab, tabId);
+    this.emit("tab-adopted", adoptingTab, adoptedTab);
+    if (this.has("tab-detached")) {
+      let nativeTab = adoptedTab;
+      let adoptedBy = adoptingTab;
+      let oldWindowId = windowTracker.getId(nativeTab.ownerGlobal);
+      let oldPosition = nativeTab._tPos;
+      this.emit("tab-detached", {
+        nativeTab,
+        adoptedBy,
+        tabId,
+        oldWindowId,
+        oldPosition,
+      });
+    }
+    if (this.has("tab-attached")) {
+      let nativeTab = adoptingTab;
+      let newWindowId = windowTracker.getId(nativeTab.ownerGlobal);
+      let newPosition = nativeTab._tPos;
+      this.emit("tab-attached", {
+        nativeTab,
+        tabId,
+        newWindowId,
+        newPosition,
+      });
+    }
+  }
+
+  _handleTabDestroyed(event, { nativeTab }) {
+    let id = this._tabs.get(nativeTab);
+    if (id) {
+      this._tabs.delete(nativeTab);
+      if (this._tabIds.get(id) === nativeTab) {
+        this._tabIds.delete(id);
+      }
+    }
+  }
+
+  /**
+   * Returns the XUL <tab> element associated with the given tab ID. If no tab
+   * with the given ID exists, and no default value is provided, an error is
+   * raised, belonging to the scope of the given context.
+   *
+   * @param {integer} tabId
+   *        The ID of the tab to retrieve.
+   * @param {*} default_
+   *        The value to return if no tab exists with the given ID.
+   * @returns {Element<tab>}
+   *        A XUL <tab> element.
+   */
+  getTab(tabId, default_ = undefined) {
+    let nativeTab = this._tabIds.get(tabId);
+    if (nativeTab) {
+      return nativeTab;
+    }
+    if (default_ !== undefined) {
+      return default_;
+    }
+    throw new ExtensionError(`Invalid tab ID: ${tabId}`);
+  }
+
+  /**
+   * Sets the opener of `tab` to the ID `openerTab`. Both tabs must be in the
+   * same window, or this function will throw a type error.
+   *
+   * @param {Element} tab The tab for which to set the owner.
+   * @param {Element} openerTab The opener of <tab>.
+   */
+  setOpener(tab, openerTab) {
+    if (tab.ownerDocument !== openerTab.ownerDocument) {
+      throw new Error("Tab must be in the same window as its opener");
+    }
+    tab.openerTab = openerTab;
+  }
+
+  deferredForTabOpen(nativeTab) {
+    let deferred = this._deferredTabOpenEvents.get(nativeTab);
+    if (!deferred) {
+      deferred = PromiseUtils.defer();
+      this._deferredTabOpenEvents.set(nativeTab, deferred);
+      deferred.promise.then(() => {
+        this._deferredTabOpenEvents.delete(nativeTab);
+      });
+    }
+    return deferred;
+  }
+
+  async maybeWaitForTabOpen(nativeTab) {
+    let deferred = this._deferredTabOpenEvents.get(nativeTab);
+    return deferred && deferred.promise;
+  }
+
+  /**
+   * @param {Event} event
+   *        The DOM Event to handle.
+   * @private
+   */
+  handleEvent(event) {
+    let nativeTab = event.target;
+
+    switch (event.type) {
+      case "TabOpen":
+        let { adoptedTab } = event.detail;
+        if (adoptedTab) {
+          // This tab is being created to adopt a tab from a different window.
+          // Handle the adoption.
+          this.adopt(nativeTab, adoptedTab);
+        } else {
+          // Save the size of the current tab, since the newly-created tab will
+          // likely be active by the time the promise below resolves and the
+          // event is dispatched.
+          const currentTab = nativeTab.ownerGlobal.gBrowser.selectedTab;
+          const { frameLoader } = currentTab.linkedBrowser;
+          const currentTabSize = {
+            width: frameLoader.lazyWidth,
+            height: frameLoader.lazyHeight,
+          };
+
+          // We need to delay sending this event until the next tick, since the
+          // tab can become selected immediately after "TabOpen", then onCreated
+          // should be fired with `active: true`.
+          let deferred = this.deferredForTabOpen(event.originalTarget);
+          Promise.resolve().then(() => {
+            deferred.resolve();
+            if (!event.originalTarget.parentNode) {
+              // If the tab is already be destroyed, do nothing.
+              return;
+            }
+            this.emitCreated(event.originalTarget, currentTabSize);
+          });
+        }
+        break;
+
+      case "TabClose":
+        let { adoptedBy } = event.detail;
+        if (adoptedBy) {
+          // This tab is being closed because it was adopted by a new window.
+          // Handle the adoption in case it was created as the first tab of a
+          // new window, and did not have an `adoptedTab` detail when it was
+          // opened.
+          this.adopt(adoptedBy, nativeTab);
+        } else {
+          this.emitRemoved(nativeTab, false);
+        }
+        break;
+
+      case "TabSelect":
+        // Because we are delaying calling emitCreated above, we also need to
+        // delay sending this event because it shouldn't fire before onCreated.
+        this.maybeWaitForTabOpen(nativeTab).then(() => {
+          if (!nativeTab.parentNode) {
+            // If the tab is already be destroyed, do nothing.
+            return;
+          }
+          this.emitActivated(nativeTab, event.detail.previousTab);
+        });
+        break;
+
+      case "TabMultiSelect":
+        if (this.has("tabs-highlighted")) {
+          // Because we are delaying calling emitCreated above, we also need to
+          // delay sending this event because it shouldn't fire before onCreated.
+          // event.target is gBrowser, so we don't use maybeWaitForTabOpen.
+          Promise.resolve().then(() => {
+            this.emitHighlighted(event.target.ownerGlobal);
+          });
+        }
+        break;
+    }
+  }
+
+  /**
+   * @param {object} message
+   *        The message to handle.
+   * @private
+   */
+  receiveMessage(message) {
+    switch (message.name) {
+      case "Reader:UpdateReaderButton":
+        if (message.data && message.data.isArticle !== undefined) {
+          this.emit("tab-isarticle", message);
+        }
+        break;
+    }
+  }
+
+  /**
+   * A private method which is called whenever a new browser window is opened,
+   * and dispatches the necessary events for it.
+   *
+   * @param {DOMWindow} window
+   *        The window being opened.
+   * @private
+   */
+  _handleWindowOpen(window) {
+    const tabToAdopt = window.gBrowserInit.getTabToAdopt();
+    if (tabToAdopt) {
+      // Note that this event handler depends on running before the
+      // delayed startup code in browser.js, which is currently triggered
+      // by the first MozAfterPaint event. That code handles finally
+      // adopting the tab, and clears it from the arguments list in the
+      // process, so if we run later than it, we're too late.
+      let adoptedBy = window.gBrowser.tabs[0];
+      this.adopt(adoptedBy, tabToAdopt);
+    } else {
+      for (let nativeTab of window.gBrowser.tabs) {
+        this.emitCreated(nativeTab);
+      }
+
+      // emitActivated to trigger tab.onActivated/tab.onHighlighted for a newly opened window.
+      this.emitActivated(window.gBrowser.tabs[0]);
+      if (this.has("tabs-highlighted")) {
+        this.emitHighlighted(window);
+      }
+    }
+  }
+
+  /**
+   * A private method which is called whenever a browser window is closed,
+   * and dispatches the necessary events for it.
+   *
+   * @param {DOMWindow} window
+   *        The window being closed.
+   * @private
+   */
+  _handleWindowClose(window) {
+    for (let nativeTab of window.gBrowser.tabs) {
+      if (!this.adoptedTabs.has(nativeTab)) {
+        this.emitRemoved(nativeTab, true);
+      }
+    }
+  }
+
+  /**
+   * Emits a "tab-activated" event for the given tab element.
+   *
+   * @param {NativeTab} nativeTab
+   *        The tab element which has been activated.
+   * @param {NativeTab} previousTab
+   *        The tab element which was previously activated.
+   * @private
+   */
+  emitActivated(nativeTab, previousTab = undefined) {
+    let previousTabIsPrivate, previousTabId;
+    if (previousTab && !previousTab.closing) {
+      previousTabId = this.getId(previousTab);
+      previousTabIsPrivate = isPrivateTab(previousTab);
+    }
+    this.emit("tab-activated", {
+      tabId: this.getId(nativeTab),
+      previousTabId,
+      previousTabIsPrivate,
+      windowId: windowTracker.getId(nativeTab.ownerGlobal),
+      nativeTab,
+    });
+  }
+
+  /**
+   * Emits a "tabs-highlighted" event for the given tab element.
+   *
+   * @param {ChromeWindow} window
+   *        The window in which the active tab or the set of multiselected tabs changed.
+   * @private
+   */
+  emitHighlighted(window) {
+    let tabIds = window.gBrowser.selectedTabs.map(tab => this.getId(tab));
+    let windowId = windowTracker.getId(window);
+    this.emit("tabs-highlighted", {
+      tabIds,
+      windowId,
+    });
+  }
+
+  /**
+   * Emits a "tab-created" event for the given tab element.
+   *
+   * @param {NativeTab} nativeTab
+   *        The tab element which is being created.
+   * @param {object} [currentTabSize]
+   *        The size of the tab element for the currently active tab.
+   * @private
+   */
+  emitCreated(nativeTab, currentTabSize) {
+    this.emit("tab-created", {
+      nativeTab,
+      currentTabSize,
+    });
+  }
+
+  /**
+   * Emits a "tab-removed" event for the given tab element.
+   *
+   * @param {NativeTab} nativeTab
+   *        The tab element which is being removed.
+   * @param {boolean} isWindowClosing
+   *        True if the tab is being removed because the browser window is
+   *        closing.
+   * @private
+   */
+  emitRemoved(nativeTab, isWindowClosing) {
+    let windowId = windowTracker.getId(nativeTab.ownerGlobal);
+    let tabId = this.getId(nativeTab);
+
+    this.emit("tab-removed", {
+      nativeTab,
+      tabId,
+      windowId,
+      isWindowClosing,
+    });
+  }
+
+  getBrowserData(browser) {
+    let window = browser.ownerGlobal;
+    if (!window) {
+      return {
+        tabId: -1,
+        windowId: -1,
+      };
+    }
+    let { gBrowser } = window;
+    // Some non-browser windows have gBrowser but not getTabForBrowser!
+    if (!gBrowser || !gBrowser.getTabForBrowser) {
+      if (window.top.document.documentURI === "about:addons") {
+        // When we're loaded into a <browser> inside about:addons, we need to go up
+        // one more level.
+        browser = window.docShell.chromeEventHandler;
+
+        ({ gBrowser } = browser.ownerGlobal);
+      } else {
+        return {
+          tabId: -1,
+          windowId: -1,
+        };
+      }
+    }
+
+    return {
+      tabId: this.getBrowserTabId(browser),
+      windowId: windowTracker.getId(browser.ownerGlobal),
+    };
+  }
+
+  get activeTab() {
+    let window = windowTracker.topWindow;
+    if (window && window.gBrowser) {
+      return window.gBrowser.selectedTab;
+    }
+    return null;
+  }
+}
+
+windowTracker = new WindowTracker();
+tabTracker = new TabTracker();
+
+Object.assign(global, { tabTracker, windowTracker });
+
+class Tab extends TabBase {
+  get _favIconUrl() {
+    return this.window.gBrowser.getIcon(this.nativeTab);
+  }
+
+  get attention() {
+    return this.nativeTab.hasAttribute("attention");
+  }
+
+  get audible() {
+    return this.nativeTab.soundPlaying;
+  }
+
+  get browser() {
+    return this.nativeTab.linkedBrowser;
+  }
+
+  get discarded() {
+    return !this.nativeTab.linkedPanel;
+  }
+
+  get frameLoader() {
+    // If we don't have a frameLoader yet, just return a dummy with no width and
+    // height.
+    return super.frameLoader || { lazyWidth: 0, lazyHeight: 0 };
+  }
+
+  get hidden() {
+    return this.nativeTab.hidden;
+  }
+
+  get sharingState() {
+    return this.window.gBrowser.getTabSharingState(this.nativeTab);
+  }
+
+  get cookieStoreId() {
+    return getCookieStoreIdForTab(this, this.nativeTab);
+  }
+
+  get openerTabId() {
+    let opener = this.nativeTab.openerTab;
+    if (
+      opener &&
+      opener.parentNode &&
+      opener.ownerDocument == this.nativeTab.ownerDocument
+    ) {
+      return tabTracker.getId(opener);
+    }
+    return null;
+  }
+
+  get height() {
+    return this.frameLoader.lazyHeight;
+  }
+
+  get index() {
+    return this.nativeTab._tPos;
+  }
+
+  get mutedInfo() {
+    let { nativeTab } = this;
+
+    let mutedInfo = { muted: nativeTab.muted };
+    if (nativeTab.muteReason === null) {
+      mutedInfo.reason = "user";
+    } else if (nativeTab.muteReason) {
+      mutedInfo.reason = "extension";
+      mutedInfo.extensionId = nativeTab.muteReason;
+    }
+
+    return mutedInfo;
+  }
+
+  get lastAccessed() {
+    return this.nativeTab.lastAccessed;
+  }
+
+  get pinned() {
+    return this.nativeTab.pinned;
+  }
+
+  get active() {
+    return this.nativeTab.selected;
+  }
+
+  get highlighted() {
+    let { selected, multiselected } = this.nativeTab;
+    return selected || multiselected;
+  }
+
+  get status() {
+    if (this.nativeTab.getAttribute("busy") === "true") {
+      return "loading";
+    }
+    return "complete";
+  }
+
+  get width() {
+    return this.frameLoader.lazyWidth;
+  }
+
+  get window() {
+    return this.nativeTab.ownerGlobal;
+  }
+
+  get windowId() {
+    return windowTracker.getId(this.window);
+  }
+
+  get isArticle() {
+    return this.nativeTab.linkedBrowser.isArticle;
+  }
+
+  get isInReaderMode() {
+    return this.url && this.url.startsWith(READER_MODE_PREFIX);
+  }
+
+  get successorTabId() {
+    const { successor } = this.nativeTab;
+    return successor ? tabTracker.getId(successor) : -1;
+  }
+
+  /**
+   * Converts session store data to an object compatible with the return value
+   * of the convert() method, representing that data.
+   *
+   * @param {Extension} extension
+   *        The extension for which to convert the data.
+   * @param {object} tabData
+   *        Session store data for a closed tab, as returned by
+   *        `SessionStore.getClosedTabData()`.
+   * @param {DOMWindow} [window = null]
+   *        The browser window which the tab belonged to before it was closed.
+   *        May be null if the window the tab belonged to no longer exists.
+   *
+   * @returns {object}
+   * @static
+   */
+  static convertFromSessionStoreClosedData(extension, tabData, window = null) {
+    let result = {
+      sessionId: String(tabData.closedId),
+      index: tabData.pos ? tabData.pos : 0,
+      windowId: window && windowTracker.getId(window),
+      highlighted: false,
+      active: false,
+      pinned: false,
+      hidden: tabData.state ? tabData.state.hidden : tabData.hidden,
+      incognito: Boolean(tabData.state && tabData.state.isPrivate),
+      lastAccessed: tabData.state
+        ? tabData.state.lastAccessed
+        : tabData.lastAccessed,
+    };
+
+    let entries = tabData.state ? tabData.state.entries : tabData.entries;
+    let lastTabIndex = tabData.state ? tabData.state.index : tabData.index;
+
+    // Tab may have empty history.
+    if (entries.length) {
+      // We need to take lastTabIndex - 1 because the index in the tab data is
+      // 1-based rather than 0-based.
+      let entry = entries[lastTabIndex - 1];
+
+      // tabData is a representation of a tab, as stored in the session data,
+      // and given that is not a real nativeTab, we only need to check if the extension
+      // has the "tabs" or host permission (because tabData represents a closed tab,
+      // and so we already know that it can't be the activeTab).
+      if (
+        extension.hasPermission("tabs") ||
+        extension.allowedOrigins.matches(entry.url)
+      ) {
+        result.url = entry.url;
+        result.title = entry.title;
+        if (tabData.image) {
+          result.favIconUrl = tabData.image;
+        }
+      }
+    }
+
+    return result;
+  }
+}
+
+class Window extends WindowBase {
+  /**
+   * Update the geometry of the browser window.
+   *
+   * @param {object} options
+   *        An object containing new values for the window's geometry.
+   * @param {integer} [options.left]
+   *        The new pixel distance of the left side of the browser window from
+   *        the left of the screen.
+   * @param {integer} [options.top]
+   *        The new pixel distance of the top side of the browser window from
+   *        the top of the screen.
+   * @param {integer} [options.width]
+   *        The new pixel width of the window.
+   * @param {integer} [options.height]
+   *        The new pixel height of the window.
+   */
+  updateGeometry(options) {
+    let { window } = this;
+
+    if (options.left !== null || options.top !== null) {
+      let left = options.left !== null ? options.left : window.screenX;
+      let top = options.top !== null ? options.top : window.screenY;
+      window.moveTo(left, top);
+    }
+
+    if (options.width !== null || options.height !== null) {
+      let width = options.width !== null ? options.width : window.outerWidth;
+      let height =
+        options.height !== null ? options.height : window.outerHeight;
+      window.resizeTo(width, height);
+    }
+  }
+
+  get _title() {
+    return this.window.document.title;
+  }
+
+  setTitlePreface(titlePreface) {
+    this.window.document.documentElement.setAttribute(
+      "titlepreface",
+      titlePreface
+    );
+  }
+
+  get focused() {
+    return this.window.document.hasFocus();
+  }
+
+  get top() {
+    return this.window.screenY;
+  }
+
+  get left() {
+    return this.window.screenX;
+  }
+
+  get width() {
+    return this.window.outerWidth;
+  }
+
+  get height() {
+    return this.window.outerHeight;
+  }
+
+  get incognito() {
+    return PrivateBrowsingUtils.isWindowPrivate(this.window);
+  }
+
+  get alwaysOnTop() {
+    return this.appWindow.zLevel >= Ci.nsIAppWindow.raisedZ;
+  }
+
+  get isLastFocused() {
+    return this.window === windowTracker.topWindow;
+  }
+
+  static getState(window) {
+    const STATES = {
+      [window.STATE_MAXIMIZED]: "maximized",
+      [window.STATE_MINIMIZED]: "minimized",
+      [window.STATE_FULLSCREEN]: "fullscreen",
+      [window.STATE_NORMAL]: "normal",
+    };
+    return STATES[window.windowState];
+  }
+
+  get state() {
+    return Window.getState(this.window);
+  }
+
+  async setState(state) {
+    let { window } = this;
+
+    const expectedState = (function () {
+      switch (state) {
+        case "maximized":
+          return window.STATE_MAXIMIZED;
+        case "minimized":
+        case "docked":
+          return window.STATE_MINIMIZED;
+        case "normal":
+          return window.STATE_NORMAL;
+        case "fullscreen":
+          return window.STATE_FULLSCREEN;
+      }
+      throw new Error(`Unexpected window state: ${state}`);
+    })();
+
+    const initialState = window.windowState;
+    if (expectedState == initialState) {
+      return;
+    }
+
+    // We check for window.fullScreen here to make sure to exit fullscreen even
+    // if DOM and widget disagree on what the state is. This is a speculative
+    // fix for bug 1780876, ideally it should not be needed.
+    if (initialState == window.STATE_FULLSCREEN || window.fullScreen) {
+      window.fullScreen = false;
+    }
+
+    switch (expectedState) {
+      case window.STATE_MAXIMIZED:
+        window.maximize();
+        break;
+      case window.STATE_MINIMIZED:
+        window.minimize();
+        break;
+
+      case window.STATE_NORMAL:
+        // Restore sometimes returns the window to its previous state, rather
+        // than to the "normal" state, so it may need to be called anywhere from
+        // zero to two times.
+        window.restore();
+        if (window.windowState !== window.STATE_NORMAL) {
+          window.restore();
+        }
+        break;
+
+      case window.STATE_FULLSCREEN:
+        window.fullScreen = true;
+        break;
+
+      default:
+        throw new Error(`Unexpected window state: ${state}`);
+    }
+
+    if (window.windowState != expectedState) {
+      // On Linux, sizemode changes are asynchronous. Some of them might not
+      // even happen if the window manager doesn't want to, so wait for a bit
+      // instead of forever for a sizemode change that might not ever happen.
+      const noWindowManagerTimeout = 2000;
+
+      let onSizeModeChange;
+      const promiseExpectedSizeMode = new Promise(resolve => {
+        onSizeModeChange = function () {
+          if (window.windowState == expectedState) {
+            resolve();
+          }
+        };
+        window.addEventListener("sizemodechange", onSizeModeChange);
+      });
+
+      await Promise.any([
+        promiseExpectedSizeMode,
+        new Promise(resolve => setTimeout(resolve, noWindowManagerTimeout)),
+      ]);
+
+      window.removeEventListener("sizemodechange", onSizeModeChange);
+    }
+  }
+
+  *getTabs() {
+    // A new window is being opened and it is adopting an existing tab, we return
+    // an empty iterator here because there should be no other tabs to return during
+    // that duration (See Bug 1458918 for a rationale).
+    if (this.window.gBrowserInit.isAdoptingTab()) {
+      return;
+    }
+
+    let { tabManager } = this.extension;
+
+    for (let nativeTab of this.window.gBrowser.tabs) {
+      let tab = tabManager.getWrapper(nativeTab);
+      if (tab) {
+        yield tab;
+      }
+    }
+  }
+
+  *getHighlightedTabs() {
+    let { tabManager } = this.extension;
+    for (let nativeTab of this.window.gBrowser.selectedTabs) {
+      let tab = tabManager.getWrapper(nativeTab);
+      if (tab) {
+        yield tab;
+      }
+    }
+  }
+
+  get activeTab() {
+    let { tabManager } = this.extension;
+
+    // A new window is being opened and it is adopting a tab, and we do not create
+    // a TabWrapper for the tab being adopted because it will go away once the tab
+    // adoption has been completed (See Bug 1458918 for rationale).
+    if (this.window.gBrowserInit.isAdoptingTab()) {
+      return null;
+    }
+
+    return tabManager.getWrapper(this.window.gBrowser.selectedTab);
+  }
+
+  getTabAtIndex(index) {
+    let nativeTab = this.window.gBrowser.tabs[index];
+    if (nativeTab) {
+      return this.extension.tabManager.getWrapper(nativeTab);
+    }
+  }
+
+  /**
+   * Converts session store data to an object compatible with the return value
+   * of the convert() method, representing that data.
+   *
+   * @param {Extension} extension
+   *        The extension for which to convert the data.
+   * @param {object} windowData
+   *        Session store data for a closed window, as returned by
+   *        `SessionStore.getClosedWindowData()`.
+   *
+   * @returns {object}
+   * @static
+   */
+  static convertFromSessionStoreClosedData(extension, windowData) {
+    let result = {
+      sessionId: String(windowData.closedId),
+      focused: false,
+      incognito: false,
+      type: "normal", // this is always "normal" for a closed window
+      // Bug 1781226: we assert "state" is "normal" in tests, but we could use
+      // the "sizemode" property if we wanted.
+      state: "normal",
+      alwaysOnTop: false,
+    };
+
+    if (windowData.tabs.length) {
+      result.tabs = windowData.tabs.map(tabData => {
+        return Tab.convertFromSessionStoreClosedData(extension, tabData);
+      });
+    }
+
+    return result;
+  }
+}
+
+Object.assign(global, { Tab, Window });
+
+class TabManager extends TabManagerBase {
+  get(tabId, default_ = undefined) {
+    let nativeTab = tabTracker.getTab(tabId, default_);
+
+    if (nativeTab) {
+      if (!this.canAccessTab(nativeTab)) {
+        throw new ExtensionError(`Invalid tab ID: ${tabId}`);
+      }
+      return this.getWrapper(nativeTab);
+    }
+    return default_;
+  }
+
+  addActiveTabPermission(nativeTab = tabTracker.activeTab) {
+    return super.addActiveTabPermission(nativeTab);
+  }
+
+  revokeActiveTabPermission(nativeTab = tabTracker.activeTab) {
+    return super.revokeActiveTabPermission(nativeTab);
+  }
+
+  canAccessTab(nativeTab) {
+    // Check private browsing access at browser window level.
+    if (!this.extension.canAccessWindow(nativeTab.ownerGlobal)) {
+      return false;
+    }
+    if (
+      this.extension.userContextIsolation &&
+      !this.extension.canAccessContainer(nativeTab.userContextId)
+    ) {
+      return false;
+    }
+    return true;
+  }
+
+  wrapTab(nativeTab) {
+    return new Tab(this.extension, nativeTab, tabTracker.getId(nativeTab));
+  }
+
+  getWrapper(nativeTab) {
+    if (!nativeTab.ownerGlobal.gBrowserInit.isAdoptingTab()) {
+      return super.getWrapper(nativeTab);
+    }
+  }
+}
+
+class WindowManager extends WindowManagerBase {
+  get(windowId, context) {
+    let window = windowTracker.getWindow(windowId, context);
+
+    return this.getWrapper(window);
+  }
+
+  *getAll(context) {
+    for (let window of windowTracker.browserWindows()) {
+      if (!this.canAccessWindow(window, context)) {
+        continue;
+      }
+      let wrapped = this.getWrapper(window);
+      if (wrapped) {
+        yield wrapped;
+      }
+    }
+  }
+
+  wrapWindow(window) {
+    return new Window(this.extension, window, windowTracker.getId(window));
+  }
+}
+
+// eslint-disable-next-line mozilla/balanced-listeners
+extensions.on("startup", (type, extension) => {
+  defineLazyGetter(extension, "tabManager", () => new TabManager(extension));
+  defineLazyGetter(
+    extension,
+    "windowManager",
+    () => new WindowManager(extension)
+  );
+});
diff --git a/browser/components/extensions/parent/ext-browserAction.js b/browser/components/extensions/parent/ext-browserAction.js
new file mode 100644
index 0000000000..92555c54a5
--- /dev/null
+++ b/browser/components/extensions/parent/ext-browserAction.js
@@ -0,0 +1,992 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  CustomizableUI: "resource:///modules/CustomizableUI.sys.mjs",
+  ExtensionTelemetry: "resource://gre/modules/ExtensionTelemetry.sys.mjs",
+  OriginControls: "resource://gre/modules/ExtensionPermissions.sys.mjs",
+  ViewPopup: "resource:///modules/ExtensionPopups.sys.mjs",
+  clearTimeout: "resource://gre/modules/Timer.sys.mjs",
+  setTimeout: "resource://gre/modules/Timer.sys.mjs",
+});
+ChromeUtils.defineModuleGetter(
+  this,
+  "BrowserUsageTelemetry",
+  "resource:///modules/BrowserUsageTelemetry.jsm"
+);
+
+var { DefaultWeakMap, ExtensionError } = ExtensionUtils;
+
+var { ExtensionParent } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionParent.sys.mjs"
+);
+var { BrowserActionBase } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionActions.sys.mjs"
+);
+
+var { IconDetails, StartupCache } = ExtensionParent;
+
+const POPUP_PRELOAD_TIMEOUT_MS = 200;
+
+// WeakMap[Extension -> BrowserAction]
+const browserActionMap = new WeakMap();
+
+XPCOMUtils.defineLazyGetter(this, "browserAreas", () => {
+  return {
+    navbar: CustomizableUI.AREA_NAVBAR,
+    menupanel: CustomizableUI.AREA_ADDONS,
+    tabstrip: CustomizableUI.AREA_TABSTRIP,
+    personaltoolbar: CustomizableUI.AREA_BOOKMARKS,
+  };
+});
+
+function actionWidgetId(widgetId) {
+  return `${widgetId}-browser-action`;
+}
+
+class BrowserAction extends BrowserActionBase {
+  constructor(extension, buttonDelegate) {
+    let tabContext = new TabContext(target => {
+      let window = target.ownerGlobal;
+      if (target === window) {
+        return this.getContextData(null);
+      }
+      return tabContext.get(window);
+    });
+    super(tabContext, extension);
+    this.buttonDelegate = buttonDelegate;
+  }
+
+  updateOnChange(target) {
+    if (target) {
+      let window = target.ownerGlobal;
+      if (target === window || target.selected) {
+        this.buttonDelegate.updateWindow(window);
+      }
+    } else {
+      for (let window of windowTracker.browserWindows()) {
+        this.buttonDelegate.updateWindow(window);
+      }
+    }
+  }
+
+  getTab(tabId) {
+    if (tabId !== null) {
+      return tabTracker.getTab(tabId);
+    }
+    return null;
+  }
+
+  getWindow(windowId) {
+    if (windowId !== null) {
+      return windowTracker.getWindow(windowId);
+    }
+    return null;
+  }
+
+  dispatchClick(tab, clickInfo) {
+    this.buttonDelegate.emit("click", tab, clickInfo);
+  }
+}
+
+this.browserAction = class extends ExtensionAPIPersistent {
+  static for(extension) {
+    return browserActionMap.get(extension);
+  }
+
+  async onManifestEntry(entryName) {
+    let { extension } = this;
+
+    let options =
+      extension.manifest.browser_action || extension.manifest.action;
+
+    this.action = new BrowserAction(extension, this);
+    await this.action.loadIconData();
+
+    this.iconData = new DefaultWeakMap(icons => this.getIconData(icons));
+    this.iconData.set(
+      this.action.getIcon(),
+      await StartupCache.get(
+        extension,
+        ["browserAction", "default_icon_data"],
+        () => this.getIconData(this.action.getIcon())
+      )
+    );
+
+    let widgetId = makeWidgetId(extension.id);
+    this.id = actionWidgetId(widgetId);
+    this.viewId = `PanelUI-webext-${widgetId}-BAV`;
+    this.widget = null;
+
+    this.pendingPopup = null;
+    this.pendingPopupTimeout = null;
+    this.eventQueue = [];
+
+    this.tabManager = extension.tabManager;
+    this.browserStyle = options.browser_style;
+
+    browserActionMap.set(extension, this);
+
+    this.build();
+  }
+
+  static onUpdate(id, manifest) {
+    if (!("browser_action" in manifest || "action" in manifest)) {
+      // If the new version has no browser action then mark this widget as
+      // hidden in the telemetry. If it is already marked hidden then this will
+      // do nothing.
+      BrowserUsageTelemetry.recordWidgetChange(
+        actionWidgetId(makeWidgetId(id)),
+        null,
+        "addon"
+      );
+    }
+  }
+
+  static onDisable(id) {
+    BrowserUsageTelemetry.recordWidgetChange(
+      actionWidgetId(makeWidgetId(id)),
+      null,
+      "addon"
+    );
+  }
+
+  static onUninstall(id) {
+    // If the telemetry already has this widget as hidden then this will not
+    // record anything.
+    BrowserUsageTelemetry.recordWidgetChange(
+      actionWidgetId(makeWidgetId(id)),
+      null,
+      "addon"
+    );
+  }
+
+  onShutdown() {
+    browserActionMap.delete(this.extension);
+    this.action.onShutdown();
+
+    CustomizableUI.destroyWidget(this.id);
+
+    this.clearPopup();
+  }
+
+  build() {
+    let { extension } = this;
+    let widgetId = makeWidgetId(extension.id);
+    let widget = CustomizableUI.createWidget({
+      id: this.id,
+      viewId: this.viewId,
+      type: "custom",
+      webExtension: true,
+      removable: true,
+      label: this.action.getProperty(null, "title"),
+      tooltiptext: this.action.getProperty(null, "title"),
+      defaultArea: browserAreas[this.action.getDefaultArea()],
+      showInPrivateBrowsing: extension.privateBrowsingAllowed,
+      disallowSubView: true,
+
+      // Don't attempt to load properties from the built-in widget string
+      // bundle.
+      localized: false,
+
+      // Build a custom widget that looks like a `unified-extensions-item`
+      // custom element.
+      onBuild(document) {
+        let viewId = widgetId + "-BAP";
+        let button = document.createXULElement("toolbarbutton");
+        button.setAttribute("id", viewId);
+        // Ensure the extension context menuitems are available by setting this
+        // on all button children and the item.
+        button.setAttribute("data-extensionid", extension.id);
+        button.classList.add("unified-extensions-item-action-button");
+
+        let contents = document.createXULElement("vbox");
+        contents.classList.add("unified-extensions-item-contents");
+        contents.setAttribute("move-after-stack", "true");
+
+        let name = document.createXULElement("label");
+        name.classList.add("unified-extensions-item-name");
+        contents.appendChild(name);
+
+        // This deck (and its labels) should be kept in sync with
+        // `browser/base/content/unified-extensions-viewcache.inc.xhtml`.
+        let deck = document.createXULElement("deck");
+        deck.classList.add("unified-extensions-item-message-deck");
+
+        let messageDefault = document.createXULElement("label");
+        messageDefault.classList.add(
+          "unified-extensions-item-message",
+          "unified-extensions-item-message-default"
+        );
+        deck.appendChild(messageDefault);
+
+        let messageHover = document.createXULElement("label");
+        messageHover.classList.add(
+          "unified-extensions-item-message",
+          "unified-extensions-item-message-hover"
+        );
+        deck.appendChild(messageHover);
+
+        let messageHoverForMenuButton = document.createXULElement("label");
+        messageHoverForMenuButton.classList.add(
+          "unified-extensions-item-message",
+          "unified-extensions-item-message-hover-menu-button"
+        );
+        messageHoverForMenuButton.setAttribute(
+          "data-l10n-id",
+          "unified-extensions-item-message-manage"
+        );
+        deck.appendChild(messageHoverForMenuButton);
+
+        contents.appendChild(deck);
+
+        button.appendChild(contents);
+
+        let menuButton = document.createXULElement("toolbarbutton");
+        menuButton.classList.add(
+          "toolbarbutton-1",
+          "unified-extensions-item-menu-button"
+        );
+
+        menuButton.setAttribute(
+          "data-l10n-id",
+          "unified-extensions-item-open-menu"
+        );
+        // Allow the users to quickly move between extension items using
+        // the arrow keys, see: `PanelMultiView._isNavigableWithTabOnly()`.
+        menuButton.setAttribute("data-navigable-with-tab-only", true);
+
+        menuButton.setAttribute("data-extensionid", extension.id);
+        menuButton.setAttribute("closemenu", "none");
+
+        let node = document.createXULElement("toolbaritem");
+        node.classList.add(
+          "toolbaritem-combined-buttons",
+          "unified-extensions-item"
+        );
+        node.setAttribute("view-button-id", viewId);
+        node.setAttribute("data-extensionid", extension.id);
+        node.append(button, menuButton);
+        node.viewButton = button;
+
+        return node;
+      },
+
+      onBeforeCreated: document => {
+        let view = document.createXULElement("panelview");
+        view.id = this.viewId;
+        view.setAttribute("flex", "1");
+        view.setAttribute("extension", true);
+        view.setAttribute("neverhidden", true);
+        view.setAttribute("disallowSubView", true);
+
+        document.getElementById("appMenu-viewCache").appendChild(view);
+
+        if (
+          this.extension.hasPermission("menus") ||
+          this.extension.hasPermission("contextMenus")
+        ) {
+          document.addEventListener("popupshowing", this);
+        }
+      },
+
+      onDestroyed: document => {
+        document.removeEventListener("popupshowing", this);
+
+        let view = document.getElementById(this.viewId);
+        if (view) {
+          this.clearPopup();
+          CustomizableUI.hidePanelForNode(view);
+          view.remove();
+        }
+      },
+
+      onCreated: node => {
+        let actionButton = node.querySelector(
+          ".unified-extensions-item-action-button"
+        );
+        actionButton.classList.add("panel-no-padding");
+        actionButton.classList.add("webextension-browser-action");
+        actionButton.setAttribute("badged", "true");
+        actionButton.setAttribute("constrain-size", "true");
+        actionButton.setAttribute("data-extensionid", this.extension.id);
+
+        actionButton.onmousedown = event => this.handleEvent(event);
+        actionButton.onmouseover = event => this.handleEvent(event);
+        actionButton.onmouseout = event => this.handleEvent(event);
+        actionButton.onauxclick = event => this.handleEvent(event);
+
+        const menuButton = node.querySelector(
+          ".unified-extensions-item-menu-button"
+        );
+        menuButton.setAttribute(
+          "data-l10n-args",
+          JSON.stringify({ extensionName: this.extension.name })
+        );
+
+        menuButton.onblur = event => this.handleMenuButtonEvent(event);
+        menuButton.onfocus = event => this.handleMenuButtonEvent(event);
+        menuButton.onmouseout = event => this.handleMenuButtonEvent(event);
+        menuButton.onmouseover = event => this.handleMenuButtonEvent(event);
+
+        actionButton.onblur = event => this.handleEvent(event);
+        actionButton.onfocus = event => this.handleEvent(event);
+
+        this.updateButton(node, this.action.getContextData(null), true, false);
+      },
+
+      onBeforeCommand: (event, node) => {
+        this.lastClickInfo = {
+          button: event.button || 0,
+          modifiers: clickModifiersFromEvent(event),
+        };
+
+        // The openPopupWithoutUserInteraction flag may be set by openPopup.
+        this.openPopupWithoutUserInteraction =
+          event.detail?.openPopupWithoutUserInteraction === true;
+
+        if (
+          event.target.classList.contains(
+            "unified-extensions-item-action-button"
+          )
+        ) {
+          return "view";
+        } else if (
+          event.target.classList.contains("unified-extensions-item-menu-button")
+        ) {
+          return "command";
+        }
+      },
+
+      onCommand: event => {
+        const { target } = event;
+
+        if (event.button !== 0) {
+          return;
+        }
+
+        // Open the unified extensions context menu.
+        const popup = target.ownerDocument.getElementById(
+          "unified-extensions-context-menu"
+        );
+        // Anchor to the visible part of the button.
+        const anchor = target.firstElementChild;
+        popup.openPopup(
+          anchor,
+          "after_end",
+          0,
+          0,
+          true /* isContextMenu */,
+          false /* attributesOverride */,
+          event
+        );
+      },
+
+      onViewShowing: async event => {
+        const { extension } = this;
+
+        ExtensionTelemetry.browserActionPopupOpen.stopwatchStart(
+          extension,
+          this
+        );
+        let document = event.target.ownerDocument;
+        let tabbrowser = document.defaultView.gBrowser;
+
+        let tab = tabbrowser.selectedTab;
+
+        let popupURL = !this.openPopupWithoutUserInteraction
+          ? this.action.triggerClickOrPopup(tab, this.lastClickInfo)
+          : this.action.getPopupUrl(tab);
+
+        if (popupURL) {
+          try {
+            let popup = this.getPopup(document.defaultView, popupURL);
+            let attachPromise = popup.attach(event.target);
+            event.detail.addBlocker(attachPromise);
+            await attachPromise;
+            ExtensionTelemetry.browserActionPopupOpen.stopwatchFinish(
+              extension,
+              this
+            );
+            if (this.eventQueue.length) {
+              ExtensionTelemetry.browserActionPreloadResult.histogramAdd({
+                category: "popupShown",
+                extension,
+              });
+              this.eventQueue = [];
+            }
+          } catch (e) {
+            ExtensionTelemetry.browserActionPopupOpen.stopwatchCancel(
+              extension,
+              this
+            );
+            Cu.reportError(e);
+            event.preventDefault();
+          }
+        } else {
+          ExtensionTelemetry.browserActionPopupOpen.stopwatchCancel(
+            extension,
+            this
+          );
+          // This isn't not a hack, but it seems to provide the correct behavior
+          // with the fewest complications.
+          event.preventDefault();
+          // Ensure we close any popups this node was in:
+          CustomizableUI.hidePanelForNode(event.target);
+        }
+      },
+    });
+
+    if (this.extension.startupReason != "APP_STARTUP") {
+      // Make sure the browser telemetry has the correct state for this widget.
+      // Defer loading BrowserUsageTelemetry until after startup is complete.
+      ExtensionParent.browserStartupPromise.then(() => {
+        let placement = CustomizableUI.getPlacementOfWidget(widget.id);
+        BrowserUsageTelemetry.recordWidgetChange(
+          widget.id,
+          placement?.area || null,
+          "addon"
+        );
+      });
+    }
+
+    this.widget = widget;
+  }
+
+  /**
+   * Shows the popup. The caller is expected to check if a popup is set before
+   * this is called.
+   *
+   * @param {Window} window Window to show the popup for
+   * @param {boolean} openPopupWithoutUserInteraction
+   *        If the popup was opened without user interaction
+   */
+  async openPopup(window, openPopupWithoutUserInteraction = false) {
+    const widgetForWindow = this.widget.forWindow(window);
+
+    if (!widgetForWindow.node) {
+      return;
+    }
+
+    // We want to focus hidden or minimized windows (both for the API, and to
+    // avoid an issue where showing the popup in a non-focused window
+    // immediately triggers a popuphidden event)
+    window.focus();
+
+    if (widgetForWindow.node.firstElementChild.open) {
+      return;
+    }
+
+    if (this.widget.areaType == CustomizableUI.TYPE_PANEL) {
+      await window.gUnifiedExtensions.togglePanel();
+    }
+
+    // This should already have been checked by callers, but acts as an
+    // an additional safeguard. It also makes sure we don't dispatch a click
+    // if the URL is removed while waiting for the overflow to show above.
+    if (!this.action.getPopupUrl(window.gBrowser.selectedTab)) {
+      return;
+    }
+
+    const event = new window.CustomEvent("command", {
+      bubbles: true,
+      cancelable: true,
+      detail: {
+        openPopupWithoutUserInteraction,
+      },
+    });
+    widgetForWindow.node.firstElementChild.dispatchEvent(event);
+  }
+
+  /**
+   * Triggers this browser action for the given window, with the same effects as
+   * if it were clicked by a user.
+   *
+   * This has no effect if the browser action is disabled for, or not
+   * present in, the given window.
+   *
+   * @param {Window} window
+   */
+  triggerAction(window) {
+    let popup = ViewPopup.for(this.extension, window);
+    if (!this.pendingPopup && popup) {
+      popup.closePopup();
+      return;
+    }
+
+    let tab = window.gBrowser.selectedTab;
+
+    let popupUrl = this.action.triggerClickOrPopup(tab, {
+      button: 0,
+      modifiers: [],
+    });
+    if (popupUrl) {
+      this.openPopup(window);
+    }
+  }
+
+  /**
+   * Handles events on the (secondary) menu/cog button in an extension widget.
+   *
+   * @param {Event} event
+   */
+  handleMenuButtonEvent(event) {
+    let window = event.target.ownerGlobal;
+    let { node } = window.gBrowser && this.widget.forWindow(window);
+    let messageDeck = node?.querySelector(
+      ".unified-extensions-item-message-deck"
+    );
+
+    switch (event.type) {
+      case "focus":
+      case "mouseover": {
+        if (messageDeck) {
+          messageDeck.selectedIndex =
+            window.gUnifiedExtensions.MESSAGE_DECK_INDEX_MENU_HOVER;
+        }
+        break;
+      }
+
+      case "blur":
+      case "mouseout": {
+        if (messageDeck) {
+          messageDeck.selectedIndex =
+            window.gUnifiedExtensions.MESSAGE_DECK_INDEX_DEFAULT;
+        }
+        break;
+      }
+    }
+  }
+
+  handleEvent(event) {
+    // This button is the action/primary button in the custom widget.
+    let button = event.target;
+    let window = button.ownerGlobal;
+
+    switch (event.type) {
+      case "mousedown":
+        if (event.button == 0) {
+          let tab = window.gBrowser.selectedTab;
+
+          // Begin pre-loading the browser for the popup, so it's more likely to
+          // be ready by the time we get a complete click.
+          let popupURL = this.action.getPopupUrl(tab);
+          if (
+            popupURL &&
+            (this.pendingPopup || !ViewPopup.for(this.extension, window))
+          ) {
+            // Add permission for the active tab so it will exist for the popup.
+            this.action.setActiveTabForPreload(tab);
+            this.eventQueue.push("Mousedown");
+            this.pendingPopup = this.getPopup(window, popupURL);
+            window.addEventListener("mouseup", this, true);
+          } else {
+            this.clearPopup();
+          }
+        }
+        break;
+
+      case "mouseup":
+        if (event.button == 0) {
+          this.clearPopupTimeout();
+          // If we have a pending pre-loaded popup, cancel it after we've waited
+          // long enough that we can be relatively certain it won't be opening.
+          if (this.pendingPopup) {
+            let node = window.gBrowser && this.widget.forWindow(window).node;
+            if (node && node.contains(event.originalTarget)) {
+              this.pendingPopupTimeout = setTimeout(
+                () => this.clearPopup(),
+                POPUP_PRELOAD_TIMEOUT_MS
+              );
+            } else {
+              this.clearPopup();
+            }
+          }
+        }
+        break;
+
+      case "focus":
+      case "mouseover": {
+        let tab = window.gBrowser.selectedTab;
+        let popupURL = this.action.getPopupUrl(tab);
+
+        let { node } = window.gBrowser && this.widget.forWindow(window);
+        if (node) {
+          node.querySelector(
+            ".unified-extensions-item-message-deck"
+          ).selectedIndex = window.gUnifiedExtensions.MESSAGE_DECK_INDEX_HOVER;
+        }
+
+        // We don't want to preload the popup on focus (for now).
+        if (event.type === "focus") {
+          break;
+        }
+
+        // Begin pre-loading the browser for the popup, so it's more likely to
+        // be ready by the time we get a complete click.
+        if (
+          popupURL &&
+          (this.pendingPopup || !ViewPopup.for(this.extension, window))
+        ) {
+          this.eventQueue.push("Hover");
+          this.pendingPopup = this.getPopup(window, popupURL, true);
+        }
+        break;
+      }
+
+      case "blur":
+      case "mouseout": {
+        let { node } = window.gBrowser && this.widget.forWindow(window);
+        if (node) {
+          node.querySelector(
+            ".unified-extensions-item-message-deck"
+          ).selectedIndex =
+            window.gUnifiedExtensions.MESSAGE_DECK_INDEX_DEFAULT;
+        }
+
+        // We don't want to clear the popup on blur for now.
+        if (event.type === "blur") {
+          break;
+        }
+
+        if (this.pendingPopup) {
+          if (this.eventQueue.length) {
+            ExtensionTelemetry.browserActionPreloadResult.histogramAdd({
+              category: `clearAfter${this.eventQueue.pop()}`,
+              extension: this.extension,
+            });
+            this.eventQueue = [];
+          }
+          this.clearPopup();
+        }
+        break;
+      }
+
+      case "popupshowing":
+        const menu = event.target;
+        const trigger = menu.triggerNode;
+        const node = window.document.getElementById(this.id);
+        const contexts = [
+          "toolbar-context-menu",
+          "customizationPanelItemContextMenu",
+        ];
+
+        if (contexts.includes(menu.id) && node && node.contains(trigger)) {
+          this.updateContextMenu(menu);
+        }
+        break;
+
+      case "auxclick":
+        if (event.button !== 1) {
+          return;
+        }
+
+        let tab = window.gBrowser.selectedTab;
+        if (this.action.getProperty(tab, "enabled")) {
+          this.action.setActiveTabForPreload(null);
+          this.tabManager.addActiveTabPermission(tab);
+          this.action.dispatchClick(tab, {
+            button: 1,
+            modifiers: clickModifiersFromEvent(event),
+          });
+          // Ensure we close any popups this node was in:
+          CustomizableUI.hidePanelForNode(event.target);
+        }
+        break;
+    }
+  }
+
+  /**
+   * Updates the given context menu with the extension's actions.
+   *
+   * @param {Element} menu
+   *        The context menu element that should be updated.
+   */
+  updateContextMenu(menu) {
+    const action =
+      this.extension.manifestVersion < 3 ? "onBrowserAction" : "onAction";
+
+    global.actionContextMenu({
+      extension: this.extension,
+      [action]: true,
+      menu,
+    });
+  }
+
+  /**
+   * Returns a potentially pre-loaded popup for the given URL in the given
+   * window. If a matching pre-load popup already exists, returns that.
+   * Otherwise, initializes a new one.
+   *
+   * If a pre-load popup exists which does not match, it is destroyed before a
+   * new one is created.
+   *
+   * @param {Window} window
+   *        The browser window in which to create the popup.
+   * @param {string} popupURL
+   *        The URL to load into the popup.
+   * @param {boolean} [blockParser = false]
+   *        True if the HTML parser should initially be blocked.
+   * @returns {ViewPopup}
+   */
+  getPopup(window, popupURL, blockParser = false) {
+    this.clearPopupTimeout();
+    let { pendingPopup } = this;
+    this.pendingPopup = null;
+
+    if (pendingPopup) {
+      if (
+        pendingPopup.window === window &&
+        pendingPopup.popupURL === popupURL
+      ) {
+        if (!blockParser) {
+          pendingPopup.unblockParser();
+        }
+
+        return pendingPopup;
+      }
+      pendingPopup.destroy();
+    }
+
+    return new ViewPopup(
+      this.extension,
+      window,
+      popupURL,
+      this.browserStyle,
+      false,
+      blockParser
+    );
+  }
+
+  /**
+   * Clears any pending pre-loaded popup and related timeouts.
+   */
+  clearPopup() {
+    this.clearPopupTimeout();
+    this.action.setActiveTabForPreload(null);
+    if (this.pendingPopup) {
+      this.pendingPopup.destroy();
+      this.pendingPopup = null;
+    }
+  }
+
+  /**
+   * Clears any pending timeouts to clear stale, pre-loaded popups.
+   */
+  clearPopupTimeout() {
+    if (this.pendingPopup) {
+      this.pendingPopup.window.removeEventListener("mouseup", this, true);
+    }
+
+    if (this.pendingPopupTimeout) {
+      clearTimeout(this.pendingPopupTimeout);
+      this.pendingPopupTimeout = null;
+    }
+  }
+
+  // Update the toolbar button |node| with the tab context data
+  // in |tabData|.
+  updateButton(node, tabData, sync = false, attention = false) {
+    // This is the primary/action button in the custom widget.
+    let button = node.querySelector(".unified-extensions-item-action-button");
+    let extensionTitle = tabData.title || this.extension.name;
+
+    let policy = WebExtensionPolicy.getByID(this.extension.id);
+    let messages = OriginControls.getStateMessageIDs({
+      policy,
+      tab: node.ownerGlobal.gBrowser.selectedTab,
+      isAction: true,
+      hasPopup: !!tabData.popup,
+    });
+
+    let callback = () => {
+      // This is set on the node so that it looks good in the toolbar.
+      node.toggleAttribute("attention", attention);
+
+      node.ownerDocument.l10n.setAttributes(
+        button,
+        attention
+          ? "origin-controls-toolbar-button-permission-needed"
+          : "origin-controls-toolbar-button",
+        { extensionTitle }
+      );
+
+      button.querySelector(".unified-extensions-item-name").textContent =
+        this.extension?.name;
+
+      if (messages) {
+        const messageDefaultElement = button.querySelector(
+          ".unified-extensions-item-message-default"
+        );
+        node.ownerDocument.l10n.setAttributes(
+          messageDefaultElement,
+          messages.default
+        );
+
+        const messageHoverElement = button.querySelector(
+          ".unified-extensions-item-message-hover"
+        );
+        node.ownerDocument.l10n.setAttributes(
+          messageHoverElement,
+          messages.onHover || messages.default
+        );
+      }
+
+      if (tabData.badgeText) {
+        button.setAttribute("badge", tabData.badgeText);
+      } else {
+        button.removeAttribute("badge");
+      }
+
+      if (tabData.enabled) {
+        button.removeAttribute("disabled");
+      } else {
+        button.setAttribute("disabled", "true");
+      }
+
+      let serializeColor = ([r, g, b, a]) =>
+        `rgba(${r}, ${g}, ${b}, ${a / 255})`;
+      button.setAttribute(
+        "badgeStyle",
+        [
+          `background-color: ${serializeColor(tabData.badgeBackgroundColor)}`,
+          `color: ${serializeColor(this.action.getTextColor(tabData))}`,
+        ].join("; ")
+      );
+
+      let style = this.iconData.get(tabData.icon);
+      button.setAttribute("style", style);
+    };
+    if (sync) {
+      callback();
+    } else {
+      node.ownerGlobal.requestAnimationFrame(callback);
+    }
+  }
+
+  getIconData(icons) {
+    let getIcon = (icon, theme) => {
+      if (typeof icon === "object") {
+        return IconDetails.escapeUrl(icon[theme]);
+      }
+      return IconDetails.escapeUrl(icon);
+    };
+
+    let getStyle = (name, icon) => {
+      return `
+        --webextension-${name}: url("${getIcon(icon, "default")}");
+        --webextension-${name}-light: url("${getIcon(icon, "light")}");
+        --webextension-${name}-dark: url("${getIcon(icon, "dark")}");
+      `;
+    };
+
+    let icon16 = IconDetails.getPreferredIcon(icons, this.extension, 16).icon;
+    let icon32 = IconDetails.getPreferredIcon(icons, this.extension, 32).icon;
+    let icon64 = IconDetails.getPreferredIcon(icons, this.extension, 64).icon;
+
+    return `
+        ${getStyle("menupanel-image", icon32)}
+        ${getStyle("menupanel-image-2x", icon64)}
+        ${getStyle("toolbar-image", icon16)}
+        ${getStyle("toolbar-image-2x", icon32)}
+      `;
+  }
+
+  /**
+   * Update the toolbar button for a given window.
+   *
+   * @param {ChromeWindow} window
+   *        Browser chrome window.
+   */
+  updateWindow(window) {
+    let node = this.widget.forWindow(window).node;
+    if (node) {
+      let tab = window.gBrowser.selectedTab;
+      this.updateButton(
+        node,
+        this.action.getContextData(tab),
+        false,
+        OriginControls.getAttention(this.extension.policy, window)
+      );
+    }
+  }
+
+  PERSISTENT_EVENTS = {
+    onClicked({ context, fire }) {
+      const { extension } = this;
+      const { tabManager } = extension;
+      async function listener(_event, tab, clickInfo) {
+        if (fire.wakeup) {
+          await fire.wakeup();
+        }
+        // TODO: we should double-check if the tab is already being closed by the time
+        // the background script got started and we converted the primed listener.
+        context?.withPendingBrowser(tab.linkedBrowser, () =>
+          fire.sync(tabManager.convert(tab), clickInfo)
+        );
+      }
+      this.on("click", listener);
+      return {
+        unregister: () => {
+          this.off("click", listener);
+        },
+        convert(newFire, extContext) {
+          fire = newFire;
+          context = extContext;
+        },
+      };
+    },
+  };
+
+  getAPI(context) {
+    let { extension } = context;
+    let { action } = this;
+    let namespace = extension.manifestVersion < 3 ? "browserAction" : "action";
+
+    return {
+      [namespace]: {
+        ...action.api(context),
+
+        onClicked: new EventManager({
+          context,
+          // module name is "browserAction" because it the name used in the
+          // ext-browser.json, indipendently from the manifest version.
+          module: "browserAction",
+          event: "onClicked",
+          inputHandling: true,
+          extensionApi: this,
+        }).api(),
+
+        openPopup: async options => {
+          const isHandlingUserInput =
+            context.callContextData?.isHandlingUserInput;
+
+          if (
+            !Services.prefs.getBoolPref(
+              "extensions.openPopupWithoutUserGesture.enabled"
+            ) &&
+            !isHandlingUserInput
+          ) {
+            throw new ExtensionError("openPopup requires a user gesture");
+          }
+
+          const window =
+            typeof options?.windowId === "number"
+              ? windowTracker.getWindow(options.windowId, context)
+              : windowTracker.getTopNormalWindow(context);
+
+          if (this.action.getPopupUrl(window.gBrowser.selectedTab, true)) {
+            await this.openPopup(window, !isHandlingUserInput);
+          }
+        },
+      },
+    };
+  }
+};
+
+global.browserActionFor = this.browserAction.for;
diff --git a/browser/components/extensions/parent/ext-chrome-settings-overrides.js b/browser/components/extensions/parent/ext-chrome-settings-overrides.js
new file mode 100644
index 0000000000..6c9b35d66c
--- /dev/null
+++ b/browser/components/extensions/parent/ext-chrome-settings-overrides.js
@@ -0,0 +1,577 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var { ExtensionPreferencesManager } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionPreferencesManager.sys.mjs"
+);
+var { ExtensionParent } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionParent.sys.mjs"
+);
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionControlledPopup:
+    "resource:///modules/ExtensionControlledPopup.sys.mjs",
+  ExtensionPermissions: "resource://gre/modules/ExtensionPermissions.sys.mjs",
+  ExtensionSettingsStore:
+    "resource://gre/modules/ExtensionSettingsStore.sys.mjs",
+});
+
+ChromeUtils.defineModuleGetter(
+  this,
+  "HomePage",
+  "resource:///modules/HomePage.jsm"
+);
+
+const DEFAULT_SEARCH_STORE_TYPE = "default_search";
+const DEFAULT_SEARCH_SETTING_NAME = "defaultSearch";
+
+const HOMEPAGE_PREF = "browser.startup.homepage";
+const HOMEPAGE_PRIVATE_ALLOWED =
+  "browser.startup.homepage_override.privateAllowed";
+const HOMEPAGE_EXTENSION_CONTROLLED =
+  "browser.startup.homepage_override.extensionControlled";
+const HOMEPAGE_CONFIRMED_TYPE = "homepageNotification";
+const HOMEPAGE_SETTING_TYPE = "prefs";
+const HOMEPAGE_SETTING_NAME = "homepage_override";
+
+XPCOMUtils.defineLazyGetter(this, "homepagePopup", () => {
+  return new ExtensionControlledPopup({
+    confirmedType: HOMEPAGE_CONFIRMED_TYPE,
+    observerTopic: "browser-open-homepage-start",
+    popupnotificationId: "extension-homepage-notification",
+    settingType: HOMEPAGE_SETTING_TYPE,
+    settingKey: HOMEPAGE_SETTING_NAME,
+    descriptionId: "extension-homepage-notification-description",
+    descriptionMessageId: "homepageControlled.message",
+    learnMoreMessageId: "homepageControlled.learnMore",
+    learnMoreLink: "extension-home",
+    preferencesLocation: "home-homeOverride",
+    preferencesEntrypoint: "addon-manage-home-override",
+    async beforeDisableAddon(popup, win) {
+      // Disabling an add-on should remove the tabs that it has open, but we want
+      // to open the new homepage in this tab (which might get closed).
+      //   1. Replace the tab's URL with about:blank, wait for it to change
+      //   2. Now that this tab isn't associated with the add-on, disable the add-on
+      //   3. Trigger the browser's homepage method
+      let gBrowser = win.gBrowser;
+      let tab = gBrowser.selectedTab;
+      await replaceUrlInTab(gBrowser, tab, Services.io.newURI("about:blank"));
+      Services.prefs.addObserver(HOMEPAGE_PREF, async function prefObserver() {
+        Services.prefs.removeObserver(HOMEPAGE_PREF, prefObserver);
+        let loaded = waitForTabLoaded(tab);
+        win.BrowserHome();
+        await loaded;
+        // Manually trigger an event in case this is controlled again.
+        popup.open();
+      });
+    },
+  });
+});
+
+// When the browser starts up it will trigger the observer topic we're expecting
+// but that happens before our observer has been registered. To handle the
+// startup case we need to check if the preferences are set to load the homepage
+// and check if the homepage is active, then show the doorhanger in that case.
+async function handleInitialHomepagePopup(extensionId, homepageUrl) {
+  // browser.startup.page == 1 is show homepage.
+  if (
+    Services.prefs.getIntPref("browser.startup.page") == 1 &&
+    windowTracker.topWindow
+  ) {
+    let { gBrowser } = windowTracker.topWindow;
+    let tab = gBrowser.selectedTab;
+    let currentUrl = gBrowser.currentURI.spec;
+    // When the first window is still loading the URL might be about:blank.
+    // Wait for that the actual page to load before checking the URL, unless
+    // the homepage is set to about:blank.
+    if (currentUrl != homepageUrl && currentUrl == "about:blank") {
+      await waitForTabLoaded(tab);
+      currentUrl = gBrowser.currentURI.spec;
+    }
+    // Once the page has loaded, if necessary and the active tab hasn't changed,
+    // then show the popup now.
+    if (currentUrl == homepageUrl && gBrowser.selectedTab == tab) {
+      homepagePopup.open();
+      return;
+    }
+  }
+  homepagePopup.addObserver(extensionId);
+}
+
+/**
+ * Handles the homepage url setting for an extension.
+ *
+ * @param {object} extension
+ *   The extension setting the hompage url.
+ * @param {string} homepageUrl
+ *   The homepage url to set.
+ */
+async function handleHomepageUrl(extension, homepageUrl) {
+  // For new installs and enabling a disabled addon, we will show
+  // the prompt.  We clear the confirmation in onDisabled and
+  // onUninstalled, so in either ADDON_INSTALL or ADDON_ENABLE it
+  // is already cleared, resulting in the prompt being shown if
+  // necessary the next time the homepage is shown.
+
+  // For localizing the homepageUrl, or otherwise updating the value
+  // we need to always set the setting here.
+  let inControl = await ExtensionPreferencesManager.setSetting(
+    extension.id,
+    "homepage_override",
+    homepageUrl
+  );
+
+  if (inControl) {
+    Services.prefs.setBoolPref(
+      HOMEPAGE_PRIVATE_ALLOWED,
+      extension.privateBrowsingAllowed
+    );
+    // Also set this now as an upgraded browser will need this.
+    Services.prefs.setBoolPref(HOMEPAGE_EXTENSION_CONTROLLED, true);
+    if (extension.startupReason == "APP_STARTUP") {
+      handleInitialHomepagePopup(extension.id, homepageUrl);
+    } else {
+      homepagePopup.addObserver(extension.id);
+    }
+  }
+
+  // We need to monitor permission change and update the preferences.
+  // eslint-disable-next-line mozilla/balanced-listeners
+  extension.on("add-permissions", async (ignoreEvent, permissions) => {
+    if (permissions.permissions.includes("internal:privateBrowsingAllowed")) {
+      let item = await ExtensionPreferencesManager.getSetting(
+        "homepage_override"
+      );
+      if (item && item.id == extension.id) {
+        Services.prefs.setBoolPref(HOMEPAGE_PRIVATE_ALLOWED, true);
+      }
+    }
+  });
+  // eslint-disable-next-line mozilla/balanced-listeners
+  extension.on("remove-permissions", async (ignoreEvent, permissions) => {
+    if (permissions.permissions.includes("internal:privateBrowsingAllowed")) {
+      let item = await ExtensionPreferencesManager.getSetting(
+        "homepage_override"
+      );
+      if (item && item.id == extension.id) {
+        Services.prefs.setBoolPref(HOMEPAGE_PRIVATE_ALLOWED, false);
+      }
+    }
+  });
+}
+
+// When an extension starts up, a search engine may asynchronously be
+// registered, without blocking the startup. When an extension is
+// uninstalled, we need to wait for this registration to finish
+// before running the uninstallation handler.
+// Map[extension id -> Promise]
+var pendingSearchSetupTasks = new Map();
+
+this.chrome_settings_overrides = class extends ExtensionAPI {
+  static async processDefaultSearchSetting(action, id) {
+    await ExtensionSettingsStore.initialize();
+    let item = ExtensionSettingsStore.getSetting(
+      DEFAULT_SEARCH_STORE_TYPE,
+      DEFAULT_SEARCH_SETTING_NAME,
+      id
+    );
+    if (!item) {
+      return;
+    }
+    let control = await ExtensionSettingsStore.getLevelOfControl(
+      id,
+      DEFAULT_SEARCH_STORE_TYPE,
+      DEFAULT_SEARCH_SETTING_NAME
+    );
+    item = ExtensionSettingsStore[action](
+      id,
+      DEFAULT_SEARCH_STORE_TYPE,
+      DEFAULT_SEARCH_SETTING_NAME
+    );
+    if (item && control == "controlled_by_this_extension") {
+      try {
+        let engine = Services.search.getEngineByName(
+          item.value || item.initialValue
+        );
+        if (engine) {
+          await Services.search.setDefault(
+            engine,
+            action == "enable"
+              ? Ci.nsISearchService.CHANGE_REASON_ADDON_INSTALL
+              : Ci.nsISearchService.CHANGE_REASON_ADDON_UNINSTALL
+          );
+        }
+      } catch (e) {
+        Cu.reportError(e);
+      }
+    }
+  }
+
+  static async removeEngine(id) {
+    try {
+      await Services.search.removeWebExtensionEngine(id);
+    } catch (e) {
+      Cu.reportError(e);
+    }
+  }
+
+  static removeSearchSettings(id) {
+    return Promise.all([
+      this.processDefaultSearchSetting("removeSetting", id),
+      this.removeEngine(id),
+    ]);
+  }
+
+  static async onUninstall(id) {
+    let searchStartupPromise = pendingSearchSetupTasks.get(id);
+    if (searchStartupPromise) {
+      await searchStartupPromise.catch(Cu.reportError);
+    }
+    // Note: We do not have to manage the homepage setting here
+    // as it is managed by the ExtensionPreferencesManager.
+    return Promise.all([
+      this.removeSearchSettings(id),
+      homepagePopup.clearConfirmation(id),
+    ]);
+  }
+
+  static async onUpdate(id, manifest) {
+    if (!manifest?.chrome_settings_overrides?.homepage) {
+      // New or changed values are handled during onManifest.
+      ExtensionPreferencesManager.removeSetting(id, "homepage_override");
+    }
+
+    let search_provider = manifest?.chrome_settings_overrides?.search_provider;
+
+    if (!search_provider) {
+      // Remove setting and engine from search if necessary.
+      this.removeSearchSettings(id);
+    } else if (!search_provider.is_default) {
+      // Remove the setting, but keep the engine in search.
+      chrome_settings_overrides.processDefaultSearchSetting(
+        "removeSetting",
+        id
+      );
+    }
+  }
+
+  static async onDisable(id) {
+    homepagePopup.clearConfirmation(id);
+
+    await chrome_settings_overrides.processDefaultSearchSetting("disable", id);
+    await chrome_settings_overrides.removeEngine(id);
+  }
+
+  async onManifestEntry(entryName) {
+    let { extension } = this;
+    let { manifest } = extension;
+    let homepageUrl = manifest.chrome_settings_overrides.homepage;
+
+    // If this is a page we ignore, just skip the homepage setting completely.
+    if (homepageUrl) {
+      const ignoreHomePageUrl = await HomePage.shouldIgnore(homepageUrl);
+
+      if (ignoreHomePageUrl) {
+        Services.telemetry.recordEvent(
+          "homepage",
+          "preference",
+          "ignore",
+          "set_blocked_extension",
+          {
+            webExtensionId: extension.id,
+          }
+        );
+      } else {
+        await handleHomepageUrl(extension, homepageUrl);
+      }
+    }
+    if (manifest.chrome_settings_overrides.search_provider) {
+      // Registering a search engine can potentially take a long while,
+      // or not complete at all (when searchInitialized is never resolved),
+      // so we are deliberately not awaiting the returned promise here.
+      let searchStartupPromise =
+        this.processSearchProviderManifestEntry().finally(() => {
+          if (
+            pendingSearchSetupTasks.get(extension.id) === searchStartupPromise
+          ) {
+            pendingSearchSetupTasks.delete(extension.id);
+            // This is primarily for tests so that we know when an extension
+            // has finished initialising.
+            ExtensionParent.apiManager.emit("searchEngineProcessed", extension);
+          }
+        });
+
+      // Save the promise so we can await at onUninstall.
+      pendingSearchSetupTasks.set(extension.id, searchStartupPromise);
+    }
+  }
+
+  async ensureSetting(engineName, disable = false) {
+    let { extension } = this;
+    // Ensure the addon always has a setting
+    await ExtensionSettingsStore.initialize();
+    let item = ExtensionSettingsStore.getSetting(
+      DEFAULT_SEARCH_STORE_TYPE,
+      DEFAULT_SEARCH_SETTING_NAME,
+      extension.id
+    );
+    if (!item) {
+      let defaultEngine = await Services.search.getDefault();
+      item = await ExtensionSettingsStore.addSetting(
+        extension.id,
+        DEFAULT_SEARCH_STORE_TYPE,
+        DEFAULT_SEARCH_SETTING_NAME,
+        engineName,
+        () => defaultEngine.name
+      );
+      // If there was no setting, we're fixing old behavior in this api.
+      // A lack of a setting would mean it was disabled before, disable it now.
+      disable =
+        disable ||
+        ["ADDON_UPGRADE", "ADDON_DOWNGRADE", "ADDON_ENABLE"].includes(
+          extension.startupReason
+        );
+    }
+
+    // Ensure the item is disabled (either if exists and is not default or if it does not
+    // exist yet).
+    if (disable) {
+      item = await ExtensionSettingsStore.disable(
+        extension.id,
+        DEFAULT_SEARCH_STORE_TYPE,
+        DEFAULT_SEARCH_SETTING_NAME
+      );
+    }
+    return item;
+  }
+
+  async promptDefaultSearch(engineName) {
+    let { extension } = this;
+    // Don't ask if it is already the current engine
+    let engine = Services.search.getEngineByName(engineName);
+    let defaultEngine = await Services.search.getDefault();
+    if (defaultEngine.name == engine.name) {
+      return;
+    }
+    // Ensures the setting exists and is disabled.  If the
+    // user somehow bypasses the prompt, we do not want this
+    // setting enabled for this extension.
+    await this.ensureSetting(engineName, true);
+
+    let subject = {
+      wrappedJSObject: {
+        // This is a hack because we don't have the browser of
+        // the actual install. This means the popup might show
+        // in a different window. Will be addressed in a followup bug.
+        // As well, we still notify if no topWindow exists to support
+        // testing from xpcshell.
+        browser: windowTracker.topWindow?.gBrowser.selectedBrowser,
+        id: extension.id,
+        name: extension.name,
+        icon: extension.getPreferredIcon(32),
+        currentEngine: defaultEngine.name,
+        newEngine: engineName,
+        async respond(allow) {
+          if (allow) {
+            await chrome_settings_overrides.processDefaultSearchSetting(
+              "enable",
+              extension.id
+            );
+            await Services.search.setDefault(
+              Services.search.getEngineByName(engineName),
+              Ci.nsISearchService.CHANGE_REASON_ADDON_INSTALL
+            );
+          }
+          // For testing
+          Services.obs.notifyObservers(
+            null,
+            "webextension-defaultsearch-prompt-response"
+          );
+        },
+      },
+    };
+    Services.obs.notifyObservers(subject, "webextension-defaultsearch-prompt");
+  }
+
+  async processSearchProviderManifestEntry() {
+    let { extension } = this;
+    let { manifest } = extension;
+    let searchProvider = manifest.chrome_settings_overrides.search_provider;
+
+    // If we're not being requested to be set as default, then all we need
+    // to do is to add the engine to the service. The search service can cope
+    // with receiving added engines before it is initialised, so we don't have
+    // to wait for it.  Search Service will also prevent overriding a builtin
+    // engine appropriately.
+    if (!searchProvider.is_default) {
+      await this.addSearchEngine();
+      return;
+    }
+
+    await searchInitialized;
+    if (!this.extension) {
+      Cu.reportError(
+        `Extension shut down before search provider was registered`
+      );
+      return;
+    }
+
+    let engineName = searchProvider.name.trim();
+    let result = await Services.search.maybeSetAndOverrideDefault(extension);
+    // This will only be set to true when the specified engine is an app-provided
+    // engine, or when it is an allowed add-on defined in the list stored in
+    // SearchDefaultOverrideAllowlistHandler.
+    if (result.canChangeToAppProvided) {
+      await this.setDefault(engineName, true);
+    }
+    if (!result.canInstallEngine) {
+      // This extension is overriding an app-provided one, so we don't
+      // add its engine as well.
+      return;
+    }
+    await this.addSearchEngine();
+    if (extension.startupReason === "ADDON_INSTALL") {
+      await this.promptDefaultSearch(engineName);
+    } else {
+      // Needs to be called every time to handle reenabling.
+      await this.setDefault(engineName);
+    }
+  }
+
+  async setDefault(engineName, skipEnablePrompt = false) {
+    let { extension } = this;
+
+    if (extension.startupReason === "ADDON_INSTALL") {
+      // We should only get here if an extension is setting an app-provided
+      // engine to default and we are ignoring the addons other engine settings.
+      // In this case we do not show the prompt to the user.
+      let item = await this.ensureSetting(engineName);
+      await Services.search.setDefault(
+        Services.search.getEngineByName(item.value),
+        Ci.nsISearchService.CHANGE_REASON_ADDON_INSTALL
+      );
+    } else if (
+      ["ADDON_UPGRADE", "ADDON_DOWNGRADE", "ADDON_ENABLE"].includes(
+        extension.startupReason
+      )
+    ) {
+      // We would be called for every extension being enabled, we should verify
+      // that it has control and only then set it as default
+      let control = await ExtensionSettingsStore.getLevelOfControl(
+        extension.id,
+        DEFAULT_SEARCH_STORE_TYPE,
+        DEFAULT_SEARCH_SETTING_NAME
+      );
+
+      // Check for an inconsistency between the value returned by getLevelOfcontrol
+      // and the current engine actually set.
+      if (
+        control === "controlled_by_this_extension" &&
+        Services.search.defaultEngine.name !== engineName
+      ) {
+        // Check for and fix any inconsistency between the extensions settings storage
+        // and the current engine actually set.  If settings claims the extension is default
+        // but the search service claims otherwise, select what the search service claims
+        // (See Bug 1767550).
+        const allSettings = ExtensionSettingsStore.getAllSettings(
+          DEFAULT_SEARCH_STORE_TYPE,
+          DEFAULT_SEARCH_SETTING_NAME
+        );
+        for (const setting of allSettings) {
+          if (setting.value !== Services.search.defaultEngine.name) {
+            await ExtensionSettingsStore.disable(
+              setting.id,
+              DEFAULT_SEARCH_STORE_TYPE,
+              DEFAULT_SEARCH_SETTING_NAME
+            );
+          }
+        }
+        control = await ExtensionSettingsStore.getLevelOfControl(
+          extension.id,
+          DEFAULT_SEARCH_STORE_TYPE,
+          DEFAULT_SEARCH_SETTING_NAME
+        );
+      }
+
+      if (control === "controlled_by_this_extension") {
+        await Services.search.setDefault(
+          Services.search.getEngineByName(engineName),
+          Ci.nsISearchService.CHANGE_REASON_ADDON_INSTALL
+        );
+      } else if (control === "controllable_by_this_extension") {
+        if (skipEnablePrompt) {
+          // For overriding app-provided engines, we don't prompt, so set
+          // the default straight away.
+          await chrome_settings_overrides.processDefaultSearchSetting(
+            "enable",
+            extension.id
+          );
+          await Services.search.setDefault(
+            Services.search.getEngineByName(engineName),
+            Ci.nsISearchService.CHANGE_REASON_ADDON_INSTALL
+          );
+        } else if (extension.startupReason == "ADDON_ENABLE") {
+          // This extension has precedence, but is not in control.  Ask the user.
+          await this.promptDefaultSearch(engineName);
+        }
+      }
+    }
+  }
+
+  async addSearchEngine() {
+    let { extension } = this;
+    try {
+      await Services.search.addEnginesFromExtension(extension);
+    } catch (e) {
+      Cu.reportError(e);
+      return false;
+    }
+    return true;
+  }
+};
+
+ExtensionPreferencesManager.addSetting("homepage_override", {
+  prefNames: [
+    HOMEPAGE_PREF,
+    HOMEPAGE_EXTENSION_CONTROLLED,
+    HOMEPAGE_PRIVATE_ALLOWED,
+  ],
+  // ExtensionPreferencesManager will call onPrefsChanged when control changes
+  // and it updates the preferences. We are passed the item from
+  // ExtensionSettingsStore that details what is in control. If there is an id
+  // then control has changed to an extension, if there is no id then control
+  // has been returned to the user.
+  async onPrefsChanged(item) {
+    if (item.id) {
+      homepagePopup.addObserver(item.id);
+
+      let policy = ExtensionParent.WebExtensionPolicy.getByID(item.id);
+      let allowed = policy && policy.privateBrowsingAllowed;
+      if (!policy) {
+        // We'll generally hit this path during safe mode changes.
+        let perms = await ExtensionPermissions.get(item.id);
+        allowed = perms.permissions.includes("internal:privateBrowsingAllowed");
+      }
+      Services.prefs.setBoolPref(HOMEPAGE_PRIVATE_ALLOWED, allowed);
+      Services.prefs.setBoolPref(HOMEPAGE_EXTENSION_CONTROLLED, true);
+    } else {
+      homepagePopup.removeObserver();
+
+      Services.prefs.clearUserPref(HOMEPAGE_PRIVATE_ALLOWED);
+      Services.prefs.clearUserPref(HOMEPAGE_EXTENSION_CONTROLLED);
+    }
+  },
+  setCallback(value) {
+    // Setting the pref will result in onPrefsChanged being called, which
+    // will then set HOMEPAGE_PRIVATE_ALLOWED.  We want to ensure that this
+    // pref will be set/unset as apropriate.
+    return {
+      [HOMEPAGE_PREF]: value,
+      [HOMEPAGE_EXTENSION_CONTROLLED]: !!value,
+      [HOMEPAGE_PRIVATE_ALLOWED]: false,
+    };
+  },
+});
diff --git a/browser/components/extensions/parent/ext-commands.js b/browser/components/extensions/parent/ext-commands.js
new file mode 100644
index 0000000000..88e7dae307
--- /dev/null
+++ b/browser/components/extensions/parent/ext-commands.js
@@ -0,0 +1,82 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionShortcuts: "resource://gre/modules/ExtensionShortcuts.sys.mjs",
+});
+
+this.commands = class extends ExtensionAPIPersistent {
+  PERSISTENT_EVENTS = {
+    onCommand({ fire }) {
+      let listener = (eventName, commandName) => {
+        fire.async(commandName);
+      };
+      this.on("command", listener);
+      return {
+        unregister: () => this.off("command", listener),
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+    onChanged({ fire }) {
+      let listener = (eventName, changeInfo) => {
+        fire.async(changeInfo);
+      };
+      this.on("shortcutChanged", listener);
+      return {
+        unregister: () => this.off("shortcutChanged", listener),
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+  };
+
+  static onUninstall(extensionId) {
+    return ExtensionShortcuts.removeCommandsFromStorage(extensionId);
+  }
+
+  async onManifestEntry(entryName) {
+    let shortcuts = new ExtensionShortcuts({
+      extension: this.extension,
+      onCommand: name => this.emit("command", name),
+      onShortcutChanged: changeInfo => this.emit("shortcutChanged", changeInfo),
+    });
+    this.extension.shortcuts = shortcuts;
+    await shortcuts.loadCommands();
+    await shortcuts.register();
+  }
+
+  onShutdown() {
+    this.extension.shortcuts.unregister();
+  }
+
+  getAPI(context) {
+    return {
+      commands: {
+        getAll: () => this.extension.shortcuts.allCommands(),
+        update: args => this.extension.shortcuts.updateCommand(args),
+        reset: name => this.extension.shortcuts.resetCommand(name),
+        onCommand: new EventManager({
+          context,
+          module: "commands",
+          event: "onCommand",
+          inputHandling: true,
+          extensionApi: this,
+        }).api(),
+        onChanged: new EventManager({
+          context,
+          module: "commands",
+          event: "onChanged",
+          extensionApi: this,
+        }).api(),
+      },
+    };
+  }
+};
diff --git a/browser/components/extensions/parent/ext-devtools-inspectedWindow.js b/browser/components/extensions/parent/ext-devtools-inspectedWindow.js
new file mode 100644
index 0000000000..9da54b9cfc
--- /dev/null
+++ b/browser/components/extensions/parent/ext-devtools-inspectedWindow.js
@@ -0,0 +1,53 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var { SpreadArgs } = ExtensionCommon;
+
+this.devtools_inspectedWindow = class extends ExtensionAPI {
+  getAPI(context) {
+    // TODO - Bug 1448878: retrieve a more detailed callerInfo object,
+    // like the filename and lineNumber of the actual extension called
+    // in the child process.
+    const callerInfo = {
+      addonId: context.extension.id,
+      url: context.extension.baseURI.spec,
+    };
+
+    return {
+      devtools: {
+        inspectedWindow: {
+          async eval(expression, options) {
+            const toolboxEvalOptions = await getToolboxEvalOptions(context);
+            const evalOptions = Object.assign({}, options, toolboxEvalOptions);
+
+            const commands = await context.getDevToolsCommands();
+            const evalResult = await commands.inspectedWindowCommand.eval(
+              callerInfo,
+              expression,
+              evalOptions
+            );
+
+            // TODO(rpl): check for additional undocumented behaviors on chrome
+            // (e.g. if we should also print error to the console or set lastError?).
+            return new SpreadArgs([evalResult.value, evalResult.exceptionInfo]);
+          },
+          async reload(options) {
+            const { ignoreCache, userAgent, injectedScript } = options || {};
+
+            const commands = await context.getDevToolsCommands();
+            commands.inspectedWindowCommand.reload(callerInfo, {
+              ignoreCache,
+              userAgent,
+              injectedScript,
+            });
+          },
+        },
+      },
+    };
+  }
+};
diff --git a/browser/components/extensions/parent/ext-devtools-network.js b/browser/components/extensions/parent/ext-devtools-network.js
new file mode 100644
index 0000000000..5c69b4a03b
--- /dev/null
+++ b/browser/components/extensions/parent/ext-devtools-network.js
@@ -0,0 +1,82 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var { SpreadArgs } = ExtensionCommon;
+
+var { ExtensionError } = ExtensionUtils;
+
+this.devtools_network = class extends ExtensionAPI {
+  getAPI(context) {
+    return {
+      devtools: {
+        network: {
+          onNavigated: new EventManager({
+            context,
+            name: "devtools.onNavigated",
+            register: fire => {
+              const listener = url => {
+                fire.async(url);
+              };
+
+              const promise = context.addOnNavigatedListener(listener);
+              return () => {
+                promise.then(() => {
+                  context.removeOnNavigatedListener(listener);
+                });
+              };
+            },
+          }).api(),
+
+          getHAR: function () {
+            return context.devToolsToolbox.getHARFromNetMonitor();
+          },
+
+          onRequestFinished: new EventManager({
+            context,
+            name: "devtools.network.onRequestFinished",
+            register: fire => {
+              const listener = data => {
+                fire.async(data);
+              };
+
+              const toolbox = context.devToolsToolbox;
+              toolbox.addRequestFinishedListener(listener);
+
+              return () => {
+                toolbox.removeRequestFinishedListener(listener);
+              };
+            },
+          }).api(),
+
+          // The following method is used internally to allow the request API
+          // piece that is running in the child process to ask the parent process
+          // to fetch response content from the back-end.
+          Request: {
+            async getContent(requestId) {
+              return context.devToolsToolbox
+                .fetchResponseContent(requestId)
+                .then(
+                  ({ content }) =>
+                    new SpreadArgs([content.text, content.mimeType])
+                )
+                .catch(err => {
+                  const debugName = context.extension.policy.debugName;
+                  const errorMsg =
+                    "Unexpected error while fetching response content";
+                  Cu.reportError(
+                    `${debugName}: ${errorMsg} for ${requestId}: ${err}`
+                  );
+                  throw new ExtensionError(errorMsg);
+                });
+            },
+          },
+        },
+      },
+    };
+  }
+};
diff --git a/browser/components/extensions/parent/ext-devtools-panels.js b/browser/components/extensions/parent/ext-devtools-panels.js
new file mode 100644
index 0000000000..9f0dba5c25
--- /dev/null
+++ b/browser/components/extensions/parent/ext-devtools-panels.js
@@ -0,0 +1,691 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var { ExtensionParent } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionParent.sys.mjs"
+);
+
+ChromeUtils.defineESModuleGetters(this, {
+  BroadcastConduit: "resource://gre/modules/ConduitsParent.sys.mjs",
+});
+
+var { watchExtensionProxyContextLoad } = ExtensionParent;
+
+var { promiseDocumentLoaded } = ExtensionUtils;
+
+const WEBEXT_PANELS_URL = "chrome://browser/content/webext-panels.xhtml";
+
+class BaseDevToolsPanel {
+  constructor(context, panelOptions) {
+    const toolbox = context.devToolsToolbox;
+    if (!toolbox) {
+      // This should never happen when this constructor is called with a valid
+      // devtools extension context.
+      throw Error("Missing mandatory toolbox");
+    }
+
+    this.context = context;
+    this.extension = context.extension;
+    this.toolbox = toolbox;
+    this.viewType = "devtools_panel";
+    this.panelOptions = panelOptions;
+    this.id = panelOptions.id;
+
+    this.unwatchExtensionProxyContextLoad = null;
+
+    // References to the panel browser XUL element and the toolbox window global which
+    // contains the devtools panel UI.
+    this.browser = null;
+    this.browserContainerWindow = null;
+  }
+
+  async createBrowserElement(window) {
+    const { toolbox } = this;
+    const { extension } = this.context;
+    const { url } = this.panelOptions || { url: "about:blank" };
+
+    this.browser = await window.getBrowser({
+      extension,
+      extensionUrl: url,
+      browserStyle: false,
+      viewType: "devtools_panel",
+      browserInsertedData: {
+        devtoolsToolboxInfo: {
+          toolboxPanelId: this.id,
+          inspectedWindowTabId: getTargetTabIdForToolbox(toolbox),
+        },
+      },
+    });
+
+    let hasTopLevelContext = false;
+
+    // Listening to new proxy contexts.
+    this.unwatchExtensionProxyContextLoad = watchExtensionProxyContextLoad(
+      this,
+      context => {
+        // Keep track of the toolbox and target associated to the context, which is
+        // needed by the API methods implementation.
+        context.devToolsToolbox = toolbox;
+
+        if (!hasTopLevelContext) {
+          hasTopLevelContext = true;
+
+          // Resolve the promise when the root devtools_panel context has been created.
+          if (this._resolveTopLevelContext) {
+            this._resolveTopLevelContext(context);
+          }
+        }
+      }
+    );
+
+    this.browser.fixupAndLoadURIString(url, {
+      triggeringPrincipal: this.context.principal,
+    });
+  }
+
+  destroyBrowserElement() {
+    const { browser, unwatchExtensionProxyContextLoad } = this;
+    if (unwatchExtensionProxyContextLoad) {
+      this.unwatchExtensionProxyContextLoad = null;
+      unwatchExtensionProxyContextLoad();
+    }
+
+    if (browser) {
+      browser.remove();
+      this.browser = null;
+    }
+  }
+}
+
+/**
+ * Represents an addon devtools panel in the main process.
+ *
+ * @param {ExtensionChildProxyContext} context
+ *        A devtools extension proxy context running in a main process.
+ * @param {object} options
+ * @param {string} options.id
+ *        The id of the addon devtools panel.
+ * @param {string} options.icon
+ *        The icon of the addon devtools panel.
+ * @param {string} options.title
+ *        The title of the addon devtools panel.
+ * @param {string} options.url
+ *        The url of the addon devtools panel, relative to the extension base URL.
+ */
+class ParentDevToolsPanel extends BaseDevToolsPanel {
+  constructor(context, panelOptions) {
+    super(context, panelOptions);
+
+    this.visible = false;
+    this.destroyed = false;
+
+    this.context.callOnClose(this);
+
+    this.conduit = new BroadcastConduit(this, {
+      id: `${this.id}-parent`,
+      send: ["PanelHidden", "PanelShown"],
+    });
+
+    this.onToolboxPanelSelect = this.onToolboxPanelSelect.bind(this);
+    this.onToolboxHostWillChange = this.onToolboxHostWillChange.bind(this);
+    this.onToolboxHostChanged = this.onToolboxHostChanged.bind(this);
+
+    this.waitTopLevelContext = new Promise(resolve => {
+      this._resolveTopLevelContext = resolve;
+    });
+
+    this.panelAdded = false;
+    this.addPanel();
+  }
+
+  addPanel() {
+    const { icon, title } = this.panelOptions;
+    const extensionName = this.context.extension.name;
+
+    this.toolbox.addAdditionalTool({
+      id: this.id,
+      extensionId: this.context.extension.id,
+      url: WEBEXT_PANELS_URL,
+      icon: icon,
+      label: title,
+      // panelLabel is used to set the aria-label attribute (See Bug 1570645).
+      panelLabel: title,
+      tooltip: `DevTools Panel added by "${extensionName}" add-on.`,
+      isToolSupported: toolbox => toolbox.commands.descriptorFront.isLocalTab,
+      build: (window, toolbox) => {
+        if (toolbox !== this.toolbox) {
+          throw new Error(
+            "Unexpected toolbox received on addAdditionalTool build property"
+          );
+        }
+
+        const destroy = this.buildPanel(window);
+
+        return { toolbox, destroy };
+      },
+    });
+
+    this.panelAdded = true;
+  }
+
+  buildPanel(window) {
+    const { toolbox } = this;
+
+    this.createBrowserElement(window);
+
+    // Store the last panel's container element (used to restore it when the toolbox
+    // host is switched between docked and undocked).
+    this.browserContainerWindow = window;
+
+    toolbox.on("select", this.onToolboxPanelSelect);
+    toolbox.on("host-will-change", this.onToolboxHostWillChange);
+    toolbox.on("host-changed", this.onToolboxHostChanged);
+
+    // Return a cleanup method that is when the panel is destroyed, e.g.
+    // - when addon devtool panel has been disabled by the user from the toolbox preferences,
+    //   its ParentDevToolsPanel instance is still valid, but the built devtools panel is removed from
+    //   the toolbox (and re-built again if the user re-enables it from the toolbox preferences panel)
+    // - when the creator context has been destroyed, the ParentDevToolsPanel close method is called,
+    //   it removes the tool definition from the toolbox, which will call this destroy method.
+    return () => {
+      this.destroyBrowserElement();
+      this.browserContainerWindow = null;
+      toolbox.off("select", this.onToolboxPanelSelect);
+      toolbox.off("host-will-change", this.onToolboxHostWillChange);
+      toolbox.off("host-changed", this.onToolboxHostChanged);
+    };
+  }
+
+  onToolboxHostWillChange() {
+    // NOTE: Using a content iframe here breaks the devtools panel
+    // switching between docked and undocked mode,
+    // because of a swapFrameLoader exception (see bug 1075490),
+    // destroy the browser and recreate it after the toolbox host has been
+    // switched is a reasonable workaround to fix the issue on release and beta
+    // Firefox versions (at least until the underlying bug can be fixed).
+    if (this.browser) {
+      // Fires a panel.onHidden event before destroying the browser element because
+      // the toolbox hosts is changing.
+      if (this.visible) {
+        this.conduit.sendPanelHidden(this.id);
+      }
+
+      this.destroyBrowserElement();
+    }
+  }
+
+  async onToolboxHostChanged() {
+    if (this.browserContainerWindow) {
+      this.createBrowserElement(this.browserContainerWindow);
+
+      // Fires a panel.onShown event once the browser element has been recreated
+      // after the toolbox hosts has been changed (needed to provide the new window
+      // object to the extension page that has created the devtools panel).
+      if (this.visible) {
+        await this.waitTopLevelContext;
+        this.conduit.sendPanelShown(this.id);
+      }
+    }
+  }
+
+  async onToolboxPanelSelect(id) {
+    if (!this.waitTopLevelContext || !this.panelAdded) {
+      return;
+    }
+
+    // Wait that the panel is fully loaded and emit show.
+    await this.waitTopLevelContext;
+
+    if (!this.visible && id === this.id) {
+      this.visible = true;
+      this.conduit.sendPanelShown(this.id);
+    } else if (this.visible && id !== this.id) {
+      this.visible = false;
+      this.conduit.sendPanelHidden(this.id);
+    }
+  }
+
+  close() {
+    const { toolbox } = this;
+
+    if (!toolbox) {
+      throw new Error("Unable to destroy a closed devtools panel");
+    }
+
+    this.conduit.close();
+
+    // Explicitly remove the panel if it is registered and the toolbox is not
+    // closing itself.
+    if (this.panelAdded && toolbox.isToolRegistered(this.id)) {
+      this.destroyBrowserElement();
+      toolbox.removeAdditionalTool(this.id);
+    }
+
+    this.waitTopLevelContext = null;
+    this._resolveTopLevelContext = null;
+    this.context = null;
+    this.toolbox = null;
+    this.browser = null;
+    this.browserContainerWindow = null;
+  }
+
+  destroyBrowserElement() {
+    super.destroyBrowserElement();
+
+    // If the panel has been removed or disabled (e.g. from the toolbox preferences
+    // or during the toolbox switching between docked and undocked),
+    // we need to re-initialize the waitTopLevelContext Promise.
+    this.waitTopLevelContext = new Promise(resolve => {
+      this._resolveTopLevelContext = resolve;
+    });
+  }
+}
+
+class DevToolsSelectionObserver extends EventEmitter {
+  constructor(context) {
+    if (!context.devToolsToolbox) {
+      // This should never happen when this constructor is called with a valid
+      // devtools extension context.
+      throw Error("Missing mandatory toolbox");
+    }
+
+    super();
+    context.callOnClose(this);
+
+    this.toolbox = context.devToolsToolbox;
+    this.onSelected = this.onSelected.bind(this);
+    this.initialized = false;
+  }
+
+  on(...args) {
+    this.lazyInit();
+    super.on.apply(this, args);
+  }
+
+  once(...args) {
+    this.lazyInit();
+    super.once.apply(this, args);
+  }
+
+  async lazyInit() {
+    if (!this.initialized) {
+      this.initialized = true;
+      this.toolbox.on("selection-changed", this.onSelected);
+    }
+  }
+
+  close() {
+    if (this.destroyed) {
+      throw new Error("Unable to close a destroyed DevToolsSelectionObserver");
+    }
+
+    if (this.initialized) {
+      this.toolbox.off("selection-changed", this.onSelected);
+    }
+
+    this.toolbox = null;
+    this.destroyed = true;
+  }
+
+  onSelected() {
+    this.emit("selectionChanged");
+  }
+}
+
+/**
+ * Represents an addon devtools inspector sidebar in the main process.
+ *
+ * @param {ExtensionChildProxyContext} context
+ *        A devtools extension proxy context running in a main process.
+ * @param {object} options
+ * @param {string} options.id
+ *        The id of the addon devtools sidebar.
+ * @param {string} options.title
+ *        The title of the addon devtools sidebar.
+ */
+class ParentDevToolsInspectorSidebar extends BaseDevToolsPanel {
+  constructor(context, panelOptions) {
+    super(context, panelOptions);
+
+    this.visible = false;
+    this.destroyed = false;
+
+    this.context.callOnClose(this);
+
+    this.conduit = new BroadcastConduit(this, {
+      id: `${this.id}-parent`,
+      send: ["InspectorSidebarHidden", "InspectorSidebarShown"],
+    });
+
+    this.onSidebarSelect = this.onSidebarSelect.bind(this);
+    this.onSidebarCreated = this.onSidebarCreated.bind(this);
+    this.onExtensionPageMount = this.onExtensionPageMount.bind(this);
+    this.onExtensionPageUnmount = this.onExtensionPageUnmount.bind(this);
+    this.onToolboxHostWillChange = this.onToolboxHostWillChange.bind(this);
+    this.onToolboxHostChanged = this.onToolboxHostChanged.bind(this);
+
+    this.toolbox.once(
+      `extension-sidebar-created-${this.id}`,
+      this.onSidebarCreated
+    );
+    this.toolbox.on("inspector-sidebar-select", this.onSidebarSelect);
+    this.toolbox.on("host-will-change", this.onToolboxHostWillChange);
+    this.toolbox.on("host-changed", this.onToolboxHostChanged);
+
+    // Set by setObject if the sidebar has not been created yet.
+    this._initializeSidebar = null;
+
+    // Set by _updateLastExpressionResult to keep track of the last
+    // object value grip (to release the previous selected actor
+    // on the remote debugging server when the actor changes).
+    this._lastExpressionResult = null;
+
+    this.toolbox.registerInspectorExtensionSidebar(this.id, {
+      title: panelOptions.title,
+    });
+  }
+
+  close() {
+    if (this.destroyed) {
+      throw new Error("Unable to close a destroyed DevToolsSelectionObserver");
+    }
+
+    this.conduit.close();
+
+    if (this.extensionSidebar) {
+      this.extensionSidebar.off(
+        "extension-page-mount",
+        this.onExtensionPageMount
+      );
+      this.extensionSidebar.off(
+        "extension-page-unmount",
+        this.onExtensionPageUnmount
+      );
+    }
+
+    if (this.browser) {
+      this.destroyBrowserElement();
+      this.browser = null;
+      this.containerEl = null;
+    }
+
+    this.toolbox.off(
+      `extension-sidebar-created-${this.id}`,
+      this.onSidebarCreated
+    );
+    this.toolbox.off("inspector-sidebar-select", this.onSidebarSelect);
+    this.toolbox.off("host-changed", this.onToolboxHostChanged);
+    this.toolbox.off("host-will-change", this.onToolboxHostWillChange);
+
+    this.toolbox.unregisterInspectorExtensionSidebar(this.id);
+    this.extensionSidebar = null;
+    this._lazySidebarInit = null;
+
+    this.destroyed = true;
+  }
+
+  onToolboxHostWillChange() {
+    if (this.browser) {
+      this.destroyBrowserElement();
+    }
+  }
+
+  onToolboxHostChanged() {
+    if (this.containerEl && this.panelOptions.url) {
+      this.createBrowserElement(this.containerEl.contentWindow);
+    }
+  }
+
+  onExtensionPageMount(containerEl) {
+    this.containerEl = containerEl;
+
+    // Wait the webext-panel.xhtml page to have been loaded in the
+    // inspector sidebar panel.
+    promiseDocumentLoaded(containerEl.contentDocument).then(() => {
+      this.createBrowserElement(containerEl.contentWindow);
+    });
+  }
+
+  onExtensionPageUnmount() {
+    this.containerEl = null;
+    this.destroyBrowserElement();
+  }
+
+  onSidebarCreated(sidebar) {
+    this.extensionSidebar = sidebar;
+
+    sidebar.on("extension-page-mount", this.onExtensionPageMount);
+    sidebar.on("extension-page-unmount", this.onExtensionPageUnmount);
+
+    const { _lazySidebarInit } = this;
+    this._lazySidebarInit = null;
+
+    if (typeof _lazySidebarInit === "function") {
+      _lazySidebarInit();
+    }
+  }
+
+  onSidebarSelect(id) {
+    if (!this.extensionSidebar) {
+      return;
+    }
+
+    if (!this.visible && id === this.id) {
+      this.visible = true;
+      this.conduit.sendInspectorSidebarShown(this.id);
+    } else if (this.visible && id !== this.id) {
+      this.visible = false;
+      this.conduit.sendInspectorSidebarHidden(this.id);
+    }
+  }
+
+  setPage(extensionPageURL) {
+    this.panelOptions.url = extensionPageURL;
+
+    if (this.extensionSidebar) {
+      if (this.browser) {
+        // Just load the new extension page url in the existing browser, if
+        // it already exists.
+        this.browser.fixupAndLoadURIString(this.panelOptions.url, {
+          triggeringPrincipal: this.context.extension.principal,
+        });
+      } else {
+        // The browser element doesn't exist yet, but the sidebar has been
+        // already created (e.g. because the inspector was already selected
+        // in a open toolbox and the extension has been installed/reloaded/updated).
+        this.extensionSidebar.setExtensionPage(WEBEXT_PANELS_URL);
+      }
+    } else {
+      // Defer the sidebar.setExtensionPage call.
+      this._setLazySidebarInit(() =>
+        this.extensionSidebar.setExtensionPage(WEBEXT_PANELS_URL)
+      );
+    }
+  }
+
+  setObject(object, rootTitle) {
+    delete this.panelOptions.url;
+
+    this._updateLastExpressionResult(null);
+
+    // Nest the object inside an object, as the value of the `rootTitle` property.
+    if (rootTitle) {
+      object = { [rootTitle]: object };
+    }
+
+    if (this.extensionSidebar) {
+      this.extensionSidebar.setObject(object);
+    } else {
+      // Defer the sidebar.setObject call.
+      this._setLazySidebarInit(() => this.extensionSidebar.setObject(object));
+    }
+  }
+
+  _setLazySidebarInit(cb) {
+    this._lazySidebarInit = cb;
+  }
+
+  setExpressionResult(expressionResult, rootTitle) {
+    delete this.panelOptions.url;
+
+    this._updateLastExpressionResult(expressionResult);
+
+    if (this.extensionSidebar) {
+      this.extensionSidebar.setExpressionResult(expressionResult, rootTitle);
+    } else {
+      // Defer the sidebar.setExpressionResult call.
+      this._setLazySidebarInit(() => {
+        this.extensionSidebar.setExpressionResult(expressionResult, rootTitle);
+      });
+    }
+  }
+
+  _updateLastExpressionResult(newExpressionResult = null) {
+    const { _lastExpressionResult } = this;
+
+    this._lastExpressionResult = newExpressionResult;
+
+    const oldActor = _lastExpressionResult && _lastExpressionResult.actorID;
+    const newActor = newExpressionResult && newExpressionResult.actorID;
+
+    // Release the previously active actor on the remote debugging server.
+    if (
+      oldActor &&
+      oldActor !== newActor &&
+      typeof _lastExpressionResult.release === "function"
+    ) {
+      _lastExpressionResult.release();
+    }
+  }
+}
+
+const sidebarsById = new Map();
+
+this.devtools_panels = class extends ExtensionAPI {
+  getAPI(context) {
+    // TODO - Bug 1448878: retrieve a more detailed callerInfo object,
+    // like the filename and lineNumber of the actual extension called
+    // in the child process.
+    const callerInfo = {
+      addonId: context.extension.id,
+      url: context.extension.baseURI.spec,
+    };
+
+    // An incremental "per context" id used in the generated devtools panel id.
+    let nextPanelId = 0;
+
+    const toolboxSelectionObserver = new DevToolsSelectionObserver(context);
+
+    function newBasePanelId() {
+      return `${context.extension.id}-${context.contextId}-${nextPanelId++}`;
+    }
+
+    return {
+      devtools: {
+        panels: {
+          elements: {
+            onSelectionChanged: new EventManager({
+              context,
+              name: "devtools.panels.elements.onSelectionChanged",
+              register: fire => {
+                const listener = eventName => {
+                  fire.async();
+                };
+                toolboxSelectionObserver.on("selectionChanged", listener);
+                return () => {
+                  toolboxSelectionObserver.off("selectionChanged", listener);
+                };
+              },
+            }).api(),
+            createSidebarPane(title) {
+              const id = `devtools-inspector-sidebar-${makeWidgetId(
+                newBasePanelId()
+              )}`;
+
+              const parentSidebar = new ParentDevToolsInspectorSidebar(
+                context,
+                { title, id }
+              );
+              sidebarsById.set(id, parentSidebar);
+
+              context.callOnClose({
+                close() {
+                  sidebarsById.delete(id);
+                },
+              });
+
+              // Resolved to the devtools sidebar id into the child addon process,
+              // where it will be used to identify the messages related
+              // to the panel API onShown/onHidden events.
+              return Promise.resolve(id);
+            },
+            // The following methods are used internally to allow the sidebar API
+            // piece that is running in the child process to asks the parent process
+            // to execute the sidebar methods.
+            Sidebar: {
+              setPage(sidebarId, extensionPageURL) {
+                const sidebar = sidebarsById.get(sidebarId);
+                return sidebar.setPage(extensionPageURL);
+              },
+              setObject(sidebarId, jsonObject, rootTitle) {
+                const sidebar = sidebarsById.get(sidebarId);
+                return sidebar.setObject(jsonObject, rootTitle);
+              },
+              async setExpression(sidebarId, evalExpression, rootTitle) {
+                const sidebar = sidebarsById.get(sidebarId);
+
+                const toolboxEvalOptions = await getToolboxEvalOptions(context);
+
+                const commands = await context.getDevToolsCommands();
+                const target = commands.targetCommand.targetFront;
+                const consoleFront = await target.getFront("console");
+                toolboxEvalOptions.consoleFront = consoleFront;
+
+                const evalResult = await commands.inspectedWindowCommand.eval(
+                  callerInfo,
+                  evalExpression,
+                  toolboxEvalOptions
+                );
+
+                let jsonObject;
+
+                if (evalResult.exceptionInfo) {
+                  jsonObject = evalResult.exceptionInfo;
+
+                  return sidebar.setObject(jsonObject, rootTitle);
+                }
+
+                return sidebar.setExpressionResult(evalResult, rootTitle);
+              },
+            },
+          },
+          create(title, icon, url) {
+            // Get a fallback icon from the manifest data.
+            if (icon === "") {
+              icon = context.extension.getPreferredIcon(128);
+            }
+
+            icon = context.extension.baseURI.resolve(icon);
+            url = context.extension.baseURI.resolve(url);
+
+            const id = `webext-devtools-panel-${makeWidgetId(
+              newBasePanelId()
+            )}`;
+
+            new ParentDevToolsPanel(context, { title, icon, url, id });
+
+            // Resolved to the devtools panel id into the child addon process,
+            // where it will be used to identify the messages related
+            // to the panel API onShown/onHidden events.
+            return Promise.resolve(id);
+          },
+        },
+      },
+    };
+  }
+};
diff --git a/browser/components/extensions/parent/ext-devtools.js b/browser/components/extensions/parent/ext-devtools.js
new file mode 100644
index 0000000000..98efd25489
--- /dev/null
+++ b/browser/components/extensions/parent/ext-devtools.js
@@ -0,0 +1,510 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/**
+ * This module provides helpers used by the other specialized `ext-devtools-*.js` modules
+ * and the implementation of the `devtools_page`.
+ */
+
+ChromeUtils.defineESModuleGetters(this, {
+  DevToolsShim: "chrome://devtools-startup/content/DevToolsShim.sys.mjs",
+});
+
+var { ExtensionParent } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionParent.sys.mjs"
+);
+
+var { HiddenExtensionPage, watchExtensionProxyContextLoad } = ExtensionParent;
+
+// Get the devtools preference given the extension id.
+function getDevToolsPrefBranchName(extensionId) {
+  return `devtools.webextensions.${extensionId}`;
+}
+
+/**
+ * Retrieve the tabId for the given devtools toolbox.
+ *
+ * @param {Toolbox} toolbox
+ *   A devtools toolbox instance.
+ *
+ * @returns {number}
+ *   The corresponding WebExtensions tabId.
+ */
+global.getTargetTabIdForToolbox = toolbox => {
+  let { descriptorFront } = toolbox.commands;
+
+  if (!descriptorFront.isLocalTab) {
+    throw new Error(
+      "Unexpected target type: only local tabs are currently supported."
+    );
+  }
+
+  let parentWindow = descriptorFront.localTab.linkedBrowser.ownerGlobal;
+  let tab = parentWindow.gBrowser.getTabForBrowser(
+    descriptorFront.localTab.linkedBrowser
+  );
+
+  return tabTracker.getId(tab);
+};
+
+// Get the WebExtensionInspectedWindowActor eval options (needed to provide the $0 and inspect
+// binding provided to the evaluated js code).
+global.getToolboxEvalOptions = async function (context) {
+  const options = {};
+  const toolbox = context.devToolsToolbox;
+  const selectedNode = toolbox.selection;
+
+  if (selectedNode && selectedNode.nodeFront) {
+    // If there is a selected node in the inspector, we hand over
+    // its actor id to the eval request in order to provide the "$0" binding.
+    options.toolboxSelectedNodeActorID = selectedNode.nodeFront.actorID;
+  }
+
+  // Provide the console actor ID to implement the "inspect" binding.
+  const consoleFront = await toolbox.target.getFront("console");
+  options.toolboxConsoleActorID = consoleFront.actor;
+
+  return options;
+};
+
+/**
+ * The DevToolsPage represents the "devtools_page" related to a particular
+ * Toolbox and WebExtension.
+ *
+ * The devtools_page contexts are invisible WebExtensions contexts, similar to the
+ * background page, associated to a single developer toolbox (e.g. If an add-on
+ * registers a devtools_page and the user opens 3 developer toolbox in 3 webpages,
+ * 3 devtools_page contexts will be created for that add-on).
+ *
+ * @param {Extension}              extension
+ *   The extension that owns the devtools_page.
+ * @param {object}                 options
+ * @param {Toolbox}                options.toolbox
+ *   The developer toolbox instance related to this devtools_page.
+ * @param {string}                 options.url
+ *   The path to the devtools page html page relative to the extension base URL.
+ * @param {DevToolsPageDefinition} options.devToolsPageDefinition
+ *   The instance of the devToolsPageDefinition class related to this DevToolsPage.
+ */
+class DevToolsPage extends HiddenExtensionPage {
+  constructor(extension, options) {
+    super(extension, "devtools_page");
+
+    this.url = extension.baseURI.resolve(options.url);
+    this.toolbox = options.toolbox;
+    this.devToolsPageDefinition = options.devToolsPageDefinition;
+
+    this.unwatchExtensionProxyContextLoad = null;
+
+    this.waitForTopLevelContext = new Promise(resolve => {
+      this.resolveTopLevelContext = resolve;
+    });
+  }
+
+  async build() {
+    await this.createBrowserElement();
+
+    // Listening to new proxy contexts.
+    this.unwatchExtensionProxyContextLoad = watchExtensionProxyContextLoad(
+      this,
+      context => {
+        // Keep track of the toolbox and target associated to the context, which is
+        // needed by the API methods implementation.
+        context.devToolsToolbox = this.toolbox;
+
+        if (!this.topLevelContext) {
+          this.topLevelContext = context;
+
+          // Ensure this devtools page is destroyed, when the top level context proxy is
+          // closed.
+          this.topLevelContext.callOnClose(this);
+
+          this.resolveTopLevelContext(context);
+        }
+      }
+    );
+
+    extensions.emit("extension-browser-inserted", this.browser, {
+      devtoolsToolboxInfo: {
+        inspectedWindowTabId: getTargetTabIdForToolbox(this.toolbox),
+        themeName: DevToolsShim.getTheme(),
+      },
+    });
+
+    this.browser.fixupAndLoadURIString(this.url, {
+      triggeringPrincipal: this.extension.principal,
+    });
+
+    await this.waitForTopLevelContext;
+  }
+
+  close() {
+    if (this.closed) {
+      throw new Error("Unable to shutdown a closed DevToolsPage instance");
+    }
+
+    this.closed = true;
+
+    // Unregister the devtools page instance from the devtools page definition.
+    this.devToolsPageDefinition.forgetForToolbox(this.toolbox);
+
+    // Unregister it from the resources to cleanup when the context has been closed.
+    if (this.topLevelContext) {
+      this.topLevelContext.forgetOnClose(this);
+    }
+
+    // Stop watching for any new proxy contexts from the devtools page.
+    if (this.unwatchExtensionProxyContextLoad) {
+      this.unwatchExtensionProxyContextLoad();
+      this.unwatchExtensionProxyContextLoad = null;
+    }
+
+    super.shutdown();
+  }
+}
+
+/**
+ * The DevToolsPageDefinitions class represents the "devtools_page" manifest property
+ * of a WebExtension.
+ *
+ * A DevToolsPageDefinition instance is created automatically when a WebExtension
+ * which contains the "devtools_page" manifest property has been loaded, and it is
+ * automatically destroyed when the related WebExtension has been unloaded,
+ * and so there will be at most one DevtoolsPageDefinition per add-on.
+ *
+ * Every time a developer tools toolbox is opened, the DevToolsPageDefinition creates
+ * and keep track of a DevToolsPage instance (which represents the actual devtools_page
+ * instance related to that particular toolbox).
+ *
+ * @param {Extension} extension
+ *   The extension that owns the devtools_page.
+ * @param {string}    url
+ *   The path to the devtools page html page relative to the extension base URL.
+ */
+class DevToolsPageDefinition {
+  constructor(extension, url) {
+    this.url = url;
+    this.extension = extension;
+
+    // Map[Toolbox -> DevToolsPage]
+    this.devtoolsPageForToolbox = new Map();
+  }
+
+  onThemeChanged(themeName) {
+    Services.ppmm.broadcastAsyncMessage("Extension:DevToolsThemeChanged", {
+      themeName,
+    });
+  }
+
+  buildForToolbox(toolbox) {
+    if (
+      !this.extension.canAccessWindow(
+        toolbox.commands.descriptorFront.localTab.ownerGlobal
+      )
+    ) {
+      // We should never create a devtools page for a toolbox related to a private browsing window
+      // if the extension is not allowed to access it.
+      return;
+    }
+
+    if (this.devtoolsPageForToolbox.has(toolbox)) {
+      return Promise.reject(
+        new Error("DevtoolsPage has been already created for this toolbox")
+      );
+    }
+
+    const devtoolsPage = new DevToolsPage(this.extension, {
+      toolbox,
+      url: this.url,
+      devToolsPageDefinition: this,
+    });
+
+    // If this is the first DevToolsPage, subscribe to the theme-changed event
+    if (this.devtoolsPageForToolbox.size === 0) {
+      DevToolsShim.on("theme-changed", this.onThemeChanged);
+    }
+    this.devtoolsPageForToolbox.set(toolbox, devtoolsPage);
+
+    return devtoolsPage.build();
+  }
+
+  shutdownForToolbox(toolbox) {
+    if (this.devtoolsPageForToolbox.has(toolbox)) {
+      const devtoolsPage = this.devtoolsPageForToolbox.get(toolbox);
+      devtoolsPage.close();
+
+      // `devtoolsPage.close()` should remove the instance from the map,
+      // raise an exception if it is still there.
+      if (this.devtoolsPageForToolbox.has(toolbox)) {
+        throw new Error(
+          `Leaked DevToolsPage instance for target "${toolbox.commands.descriptorFront.url}", extension "${this.extension.policy.debugName}"`
+        );
+      }
+
+      // If this was the last DevToolsPage, unsubscribe from the theme-changed event
+      if (this.devtoolsPageForToolbox.size === 0) {
+        DevToolsShim.off("theme-changed", this.onThemeChanged);
+      }
+      this.extension.emit("devtools-page-shutdown", toolbox);
+    }
+  }
+
+  forgetForToolbox(toolbox) {
+    this.devtoolsPageForToolbox.delete(toolbox);
+  }
+
+  /**
+   * Build the devtools_page instances for all the existing toolboxes
+   * (if the toolbox target is supported).
+   */
+  build() {
+    // Iterate over the existing toolboxes and create the devtools page for them
+    // (if the toolbox target is supported).
+    for (let toolbox of DevToolsShim.getToolboxes()) {
+      if (
+        !toolbox.commands.descriptorFront.isLocalTab ||
+        !this.extension.canAccessWindow(
+          toolbox.commands.descriptorFront.localTab.ownerGlobal
+        )
+      ) {
+        // Skip any non-local tab and private browsing windows if the extension
+        // is not allowed to access them.
+        continue;
+      }
+
+      // Ensure that the WebExtension is listed in the toolbox options.
+      toolbox.registerWebExtension(this.extension.uuid, {
+        name: this.extension.name,
+        pref: `${getDevToolsPrefBranchName(this.extension.id)}.enabled`,
+      });
+
+      this.buildForToolbox(toolbox);
+    }
+  }
+
+  /**
+   * Shutdown all the devtools_page instances.
+   */
+  shutdown() {
+    for (let toolbox of this.devtoolsPageForToolbox.keys()) {
+      this.shutdownForToolbox(toolbox);
+    }
+
+    if (this.devtoolsPageForToolbox.size > 0) {
+      throw new Error(
+        `Leaked ${this.devtoolsPageForToolbox.size} DevToolsPage instances in devtoolsPageForToolbox Map`
+      );
+    }
+  }
+}
+
+this.devtools = class extends ExtensionAPI {
+  constructor(extension) {
+    super(extension);
+
+    this._initialized = false;
+
+    // DevToolsPageDefinition instance (created in onManifestEntry).
+    this.pageDefinition = null;
+
+    this.onToolboxReady = this.onToolboxReady.bind(this);
+    this.onToolboxDestroy = this.onToolboxDestroy.bind(this);
+
+    /* eslint-disable mozilla/balanced-listeners */
+    extension.on("add-permissions", (ignoreEvent, permissions) => {
+      if (permissions.permissions.includes("devtools")) {
+        Services.prefs.setBoolPref(
+          `${getDevToolsPrefBranchName(extension.id)}.enabled`,
+          true
+        );
+
+        this._initialize();
+      }
+    });
+
+    extension.on("remove-permissions", (ignoreEvent, permissions) => {
+      if (permissions.permissions.includes("devtools")) {
+        Services.prefs.setBoolPref(
+          `${getDevToolsPrefBranchName(extension.id)}.enabled`,
+          false
+        );
+
+        this._uninitialize();
+      }
+    });
+  }
+
+  onManifestEntry() {
+    this._initialize();
+  }
+
+  static onUninstall(extensionId) {
+    // Remove the preference branch on uninstall.
+    const prefBranch = Services.prefs.getBranch(
+      `${getDevToolsPrefBranchName(extensionId)}.`
+    );
+
+    prefBranch.deleteBranch("");
+  }
+
+  _initialize() {
+    const { extension } = this;
+
+    if (!extension.hasPermission("devtools") || this._initialized) {
+      return;
+    }
+
+    this.initDevToolsPref();
+
+    // Create the devtools_page definition.
+    this.pageDefinition = new DevToolsPageDefinition(
+      extension,
+      extension.manifest.devtools_page
+    );
+
+    // Build the extension devtools_page on all existing toolboxes (if the extension
+    // devtools_page is not disabled by the related preference).
+    if (!this.isDevToolsPageDisabled()) {
+      this.pageDefinition.build();
+    }
+
+    DevToolsShim.on("toolbox-ready", this.onToolboxReady);
+    DevToolsShim.on("toolbox-destroy", this.onToolboxDestroy);
+    this._initialized = true;
+  }
+
+  _uninitialize() {
+    // devtoolsPrefBranch is set in onManifestEntry, and nullified
+    // later in onShutdown.  If it isn't set, then onManifestEntry
+    // did not initialize devtools for the extension.
+    if (!this._initialized) {
+      return;
+    }
+
+    DevToolsShim.off("toolbox-ready", this.onToolboxReady);
+    DevToolsShim.off("toolbox-destroy", this.onToolboxDestroy);
+
+    // Shutdown the extension devtools_page from all existing toolboxes.
+    this.pageDefinition.shutdown();
+    this.pageDefinition = null;
+
+    // Iterate over the existing toolboxes and unlist the devtools webextension from them.
+    for (let toolbox of DevToolsShim.getToolboxes()) {
+      toolbox.unregisterWebExtension(this.extension.uuid);
+    }
+
+    this.uninitDevToolsPref();
+    this._initialized = false;
+  }
+
+  onShutdown() {
+    this._uninitialize();
+  }
+
+  getAPI(context) {
+    return {
+      devtools: {},
+    };
+  }
+
+  onToolboxReady(toolbox) {
+    if (
+      !toolbox.commands.descriptorFront.isLocalTab ||
+      !this.extension.canAccessWindow(
+        toolbox.commands.descriptorFront.localTab.ownerGlobal
+      )
+    ) {
+      // Skip any non-local (as remote tabs are not yet supported, see Bug 1304378 for additional details
+      // related to remote targets support), and private browsing windows if the extension
+      // is not allowed to access them.
+      return;
+    }
+
+    // Ensure that the WebExtension is listed in the toolbox options.
+    toolbox.registerWebExtension(this.extension.uuid, {
+      name: this.extension.name,
+      pref: `${getDevToolsPrefBranchName(this.extension.id)}.enabled`,
+    });
+
+    // Do not build the devtools page if the extension has been disabled
+    // (e.g. based on the devtools preference).
+    if (toolbox.isWebExtensionEnabled(this.extension.uuid)) {
+      this.pageDefinition.buildForToolbox(toolbox);
+    }
+  }
+
+  onToolboxDestroy(toolbox) {
+    if (!toolbox.commands.descriptorFront.isLocalTab) {
+      // Only local tabs are currently supported (See Bug 1304378 for additional details
+      // related to remote targets support).
+      return;
+    }
+
+    this.pageDefinition.shutdownForToolbox(toolbox);
+  }
+
+  /**
+   * Initialize the DevTools preferences branch for the extension and
+   * start to observe it for changes on the "enabled" preference.
+   */
+  initDevToolsPref() {
+    const prefBranch = Services.prefs.getBranch(
+      `${getDevToolsPrefBranchName(this.extension.id)}.`
+    );
+
+    // Initialize the devtools extension preference if it doesn't exist yet.
+    if (prefBranch.getPrefType("enabled") === prefBranch.PREF_INVALID) {
+      prefBranch.setBoolPref("enabled", true);
+    }
+
+    this.devtoolsPrefBranch = prefBranch;
+    this.devtoolsPrefBranch.addObserver("enabled", this);
+  }
+
+  /**
+   * Stop from observing the DevTools preferences branch for the extension.
+   */
+  uninitDevToolsPref() {
+    this.devtoolsPrefBranch.removeObserver("enabled", this);
+    this.devtoolsPrefBranch = null;
+  }
+
+  /**
+   * Test if the extension's devtools_page has been disabled using the
+   * DevTools preference.
+   *
+   * @returns {boolean}
+   *          true if the devtools_page for this extension is disabled.
+   */
+  isDevToolsPageDisabled() {
+    return !this.devtoolsPrefBranch.getBoolPref("enabled", false);
+  }
+
+  /**
+   * Observes the changed preferences on the DevTools preferences branch
+   * related to the extension.
+   *
+   * @param {nsIPrefBranch} subject  The observed preferences branch.
+   * @param {string}        topic    The notified topic.
+   * @param {string}        prefName The changed preference name.
+   */
+  observe(subject, topic, prefName) {
+    // We are currently interested only in the "enabled" preference from the
+    // WebExtension devtools preferences branch.
+    if (subject !== this.devtoolsPrefBranch || prefName !== "enabled") {
+      return;
+    }
+
+    // Shutdown or build the devtools_page on any existing toolbox.
+    if (this.isDevToolsPageDisabled()) {
+      this.pageDefinition.shutdown();
+    } else {
+      this.pageDefinition.build();
+    }
+  }
+};
diff --git a/browser/components/extensions/parent/ext-find.js b/browser/components/extensions/parent/ext-find.js
new file mode 100644
index 0000000000..5397caa85b
--- /dev/null
+++ b/browser/components/extensions/parent/ext-find.js
@@ -0,0 +1,272 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* global tabTracker */
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  PrivateBrowsingUtils: "resource://gre/modules/PrivateBrowsingUtils.sys.mjs",
+});
+
+var { ExtensionError } = ExtensionUtils;
+
+// A mapping of top-level ExtFind actors to arrays of results in each subframe.
+let findResults = new WeakMap();
+
+function getActorForBrowsingContext(browsingContext) {
+  let windowGlobal = browsingContext.currentWindowGlobal;
+  return windowGlobal ? windowGlobal.getActor("ExtFind") : null;
+}
+
+function getTopLevelActor(browser) {
+  return getActorForBrowsingContext(browser.browsingContext);
+}
+
+function gatherActors(browsingContext) {
+  let list = [];
+
+  let actor = getActorForBrowsingContext(browsingContext);
+  if (actor) {
+    list.push({ actor, result: null });
+  }
+
+  let children = browsingContext.children;
+  for (let child of children) {
+    list.push(...gatherActors(child));
+  }
+
+  return list;
+}
+
+function mergeFindResults(params, list) {
+  let finalResult = {
+    count: 0,
+  };
+
+  if (params.includeRangeData) {
+    finalResult.rangeData = [];
+  }
+  if (params.includeRectData) {
+    finalResult.rectData = [];
+  }
+
+  let currentFramePos = -1;
+  for (let item of list) {
+    if (item.result.count == 0) {
+      continue;
+    }
+
+    // The framePos is incremented for each different document that has matches.
+    currentFramePos++;
+
+    finalResult.count += item.result.count;
+    if (params.includeRangeData && item.result.rangeData) {
+      for (let range of item.result.rangeData) {
+        range.framePos = currentFramePos;
+      }
+
+      finalResult.rangeData.push(...item.result.rangeData);
+    }
+
+    if (params.includeRectData && item.result.rectData) {
+      finalResult.rectData.push(...item.result.rectData);
+    }
+  }
+
+  return finalResult;
+}
+
+function sendMessageToAllActors(browser, message, params) {
+  for (let { actor } of gatherActors(browser.browsingContext)) {
+    actor.sendAsyncMessage("ext-Finder:" + message, params);
+  }
+}
+
+async function getFindResultsForActor(findContext, message, params) {
+  findContext.result = await findContext.actor.sendQuery(
+    "ext-Finder:" + message,
+    params
+  );
+  return findContext;
+}
+
+function queryAllActors(browser, message, params) {
+  let promises = [];
+  for (let findContext of gatherActors(browser.browsingContext)) {
+    promises.push(getFindResultsForActor(findContext, message, params));
+  }
+  return Promise.all(promises);
+}
+
+async function collectFindResults(browser, findResults, params) {
+  let results = await queryAllActors(browser, "CollectResults", params);
+  findResults.set(getTopLevelActor(browser), results);
+  return mergeFindResults(params, results);
+}
+
+async function runHighlight(browser, params) {
+  let hasResults = false;
+  let foundResults = false;
+  let list = findResults.get(getTopLevelActor(browser));
+  if (!list) {
+    return Promise.reject({ message: "no search results to highlight" });
+  }
+
+  let highlightPromises = [];
+
+  let index = params.rangeIndex;
+  const highlightAll = typeof index != "number";
+
+  for (let c = 0; c < list.length; c++) {
+    if (list[c].result.count) {
+      hasResults = true;
+    }
+
+    let actor = list[c].actor;
+    if (highlightAll) {
+      // Highlight all ranges.
+      highlightPromises.push(
+        actor.sendQuery("ext-Finder:HighlightResults", params)
+      );
+    } else if (!foundResults && index < list[c].result.count) {
+      foundResults = true;
+      params.rangeIndex = index;
+      highlightPromises.push(
+        actor.sendQuery("ext-Finder:HighlightResults", params)
+      );
+    } else {
+      highlightPromises.push(
+        actor.sendQuery("ext-Finder:ClearHighlighting", params)
+      );
+    }
+
+    index -= list[c].result.count;
+  }
+
+  let responses = await Promise.all(highlightPromises);
+  if (hasResults) {
+    if (responses.includes("OutOfRange") || index >= 0) {
+      return Promise.reject({ message: "index supplied was out of range" });
+    } else if (responses.includes("Success")) {
+      return;
+    }
+  }
+
+  return Promise.reject({ message: "no search results to highlight" });
+}
+
+/**
+ * runFindOperation
+ * Utility for `find` and `highlightResults`.
+ *
+ * @param {BaseContext} context - context the find operation runs in.
+ * @param {object} params - params to pass to message sender.
+ * @param {string} message - identifying component of message name.
+ *
+ * @returns {Promise} a promise that will be resolved or rejected based on the
+ *          data received by the message listener.
+ */
+function runFindOperation(context, params, message) {
+  let { tabId } = params;
+  let tab = tabId ? tabTracker.getTab(tabId) : tabTracker.activeTab;
+  let browser = tab.linkedBrowser;
+  tabId = tabId || tabTracker.getId(tab);
+  if (
+    !context.privateBrowsingAllowed &&
+    PrivateBrowsingUtils.isBrowserPrivate(browser)
+  ) {
+    return Promise.reject({ message: `Unable to search: ${tabId}` });
+  }
+  // We disallow find in about: urls.
+  if (
+    tab.linkedBrowser.contentPrincipal.isSystemPrincipal ||
+    (["about", "chrome", "resource"].includes(
+      tab.linkedBrowser.currentURI.scheme
+    ) &&
+      tab.linkedBrowser.currentURI.spec != "about:blank")
+  ) {
+    return Promise.reject({ message: `Unable to search: ${tabId}` });
+  }
+
+  if (message == "HighlightResults") {
+    return runHighlight(browser, params);
+  } else if (message == "CollectResults") {
+    // Remove prior highlights before starting a new find operation.
+    findResults.delete(getTopLevelActor(browser));
+    return collectFindResults(browser, findResults, params);
+  }
+}
+
+this.find = class extends ExtensionAPI {
+  getAPI(context) {
+    return {
+      find: {
+        /**
+         * browser.find.find
+         * Searches document and its frames for a given queryphrase and stores all found
+         * Range objects in an array accessible by other browser.find methods.
+         *
+         * @param {string} queryphrase - The string to search for.
+         * @param {object} params optional - may contain any of the following properties,
+         *   all of which are optional:
+         *   {number} tabId - Tab to query.  Defaults to the active tab.
+         *   {boolean} caseSensitive - Highlight only ranges with case sensitive match.
+         *   {boolean} entireWord - Highlight only ranges that match entire word.
+         *   {boolean} includeRangeData - Whether to return range data.
+         *   {boolean} includeRectData - Whether to return rectangle data.
+         *
+         * @returns {object} data received by the message listener that includes:
+         *   {number} count - number of results found.
+         *   {array} rangeData (if opted) - serialized representation of ranges found.
+         *   {array} rectData (if opted) - rect data of ranges found.
+         */
+        find(queryphrase, params) {
+          params = params || {};
+          params.queryphrase = queryphrase;
+          return runFindOperation(context, params, "CollectResults");
+        },
+
+        /**
+         * browser.find.highlightResults
+         * Highlights range(s) found in previous browser.find.find.
+         *
+         * @param {object} params optional - may contain any of the following properties,
+         *   all of which are optional:
+         *   {number} rangeIndex - Found range to be highlighted. Default highlights all ranges.
+         *   {number} tabId - Tab to highlight.  Defaults to the active tab.
+         *   {boolean} noScroll - Don't scroll to highlighted item.
+         *
+         * @returns {string} - data received by the message listener that may be:
+         *   "Success" - Highlighting succeeded.
+         *   "OutOfRange" - The index supplied was out of range.
+         *   "NoResults" - There were no search results to highlight.
+         */
+        highlightResults(params) {
+          params = params || {};
+          return runFindOperation(context, params, "HighlightResults");
+        },
+
+        /**
+         * browser.find.removeHighlighting
+         * Removes all highlighting from previous search.
+         *
+         * @param {number} tabId optional
+         *                 Tab to clear highlighting in.  Defaults to the active tab.
+         */
+        removeHighlighting(tabId) {
+          let tab = tabId ? tabTracker.getTab(tabId) : tabTracker.activeTab;
+          if (
+            !context.privateBrowsingAllowed &&
+            PrivateBrowsingUtils.isBrowserPrivate(tab.linkedBrowser)
+          ) {
+            throw new ExtensionError(`Invalid tab ID: ${tabId}`);
+          }
+          sendMessageToAllActors(tab.linkedBrowser, "ClearHighlighting", {});
+        },
+      },
+    };
+  }
+};
diff --git a/browser/components/extensions/parent/ext-history.js b/browser/components/extensions/parent/ext-history.js
new file mode 100644
index 0000000000..b7e24aecaa
--- /dev/null
+++ b/browser/components/extensions/parent/ext-history.js
@@ -0,0 +1,326 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  PlacesUtils: "resource://gre/modules/PlacesUtils.sys.mjs",
+});
+
+var { normalizeTime } = ExtensionCommon;
+
+let nsINavHistoryService = Ci.nsINavHistoryService;
+const TRANSITION_TO_TRANSITION_TYPES_MAP = new Map([
+  ["link", nsINavHistoryService.TRANSITION_LINK],
+  ["typed", nsINavHistoryService.TRANSITION_TYPED],
+  ["auto_bookmark", nsINavHistoryService.TRANSITION_BOOKMARK],
+  ["auto_subframe", nsINavHistoryService.TRANSITION_EMBED],
+  ["manual_subframe", nsINavHistoryService.TRANSITION_FRAMED_LINK],
+  ["reload", nsINavHistoryService.TRANSITION_RELOAD],
+]);
+
+let TRANSITION_TYPE_TO_TRANSITIONS_MAP = new Map();
+for (let [transition, transitionType] of TRANSITION_TO_TRANSITION_TYPES_MAP) {
+  TRANSITION_TYPE_TO_TRANSITIONS_MAP.set(transitionType, transition);
+}
+
+const getTransitionType = transition => {
+  // cannot set a default value for the transition argument as the framework sets it to null
+  transition = transition || "link";
+  let transitionType = TRANSITION_TO_TRANSITION_TYPES_MAP.get(transition);
+  if (!transitionType) {
+    throw new Error(
+      `|${transition}| is not a supported transition for history`
+    );
+  }
+  return transitionType;
+};
+
+const getTransition = transitionType => {
+  return TRANSITION_TYPE_TO_TRANSITIONS_MAP.get(transitionType) || "link";
+};
+
+/*
+ * Converts a mozIStorageRow into a HistoryItem
+ */
+const convertRowToHistoryItem = row => {
+  return {
+    id: row.getResultByName("guid"),
+    url: row.getResultByName("url"),
+    title: row.getResultByName("page_title"),
+    lastVisitTime: PlacesUtils.toDate(
+      row.getResultByName("last_visit_date")
+    ).getTime(),
+    visitCount: row.getResultByName("visit_count"),
+  };
+};
+
+/*
+ * Converts a mozIStorageRow into a VisitItem
+ */
+const convertRowToVisitItem = row => {
+  return {
+    id: row.getResultByName("guid"),
+    visitId: String(row.getResultByName("id")),
+    visitTime: PlacesUtils.toDate(row.getResultByName("visit_date")).getTime(),
+    referringVisitId: String(row.getResultByName("from_visit")),
+    transition: getTransition(row.getResultByName("visit_type")),
+  };
+};
+
+/*
+ * Converts a mozIStorageResultSet into an array of objects
+ */
+const accumulateNavHistoryResults = (resultSet, converter, results) => {
+  let row;
+  while ((row = resultSet.getNextRow())) {
+    results.push(converter(row));
+  }
+};
+
+function executeAsyncQuery(historyQuery, options, resultConverter) {
+  let results = [];
+  return new Promise((resolve, reject) => {
+    PlacesUtils.history.asyncExecuteLegacyQuery(historyQuery, options, {
+      handleResult(resultSet) {
+        accumulateNavHistoryResults(resultSet, resultConverter, results);
+      },
+      handleError(error) {
+        reject(
+          new Error(
+            "Async execution error (" + error.result + "): " + error.message
+          )
+        );
+      },
+      handleCompletion(reason) {
+        resolve(results);
+      },
+    });
+  });
+}
+
+this.history = class extends ExtensionAPIPersistent {
+  PERSISTENT_EVENTS = {
+    onVisited({ fire }) {
+      const listener = events => {
+        for (const event of events) {
+          const visit = {
+            id: event.pageGuid,
+            url: event.url,
+            title: event.lastKnownTitle || "",
+            lastVisitTime: event.visitTime,
+            visitCount: event.visitCount,
+            typedCount: event.typedCount,
+          };
+          fire.sync(visit);
+        }
+      };
+
+      PlacesUtils.observers.addListener(["page-visited"], listener);
+      return {
+        unregister() {
+          PlacesUtils.observers.removeListener(["page-visited"], listener);
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+    onVisitRemoved({ fire }) {
+      const listener = events => {
+        const removedURLs = [];
+
+        for (const event of events) {
+          switch (event.type) {
+            case "history-cleared": {
+              fire.sync({ allHistory: true, urls: [] });
+              break;
+            }
+            case "page-removed": {
+              if (!event.isPartialVisistsRemoval) {
+                removedURLs.push(event.url);
+              }
+              break;
+            }
+          }
+        }
+
+        if (removedURLs.length) {
+          fire.sync({ allHistory: false, urls: removedURLs });
+        }
+      };
+
+      PlacesUtils.observers.addListener(
+        ["history-cleared", "page-removed"],
+        listener
+      );
+      return {
+        unregister() {
+          PlacesUtils.observers.removeListener(
+            ["history-cleared", "page-removed"],
+            listener
+          );
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+    onTitleChanged({ fire }) {
+      const listener = events => {
+        for (const event of events) {
+          const titleChanged = {
+            id: event.pageGuid,
+            url: event.url,
+            title: event.title,
+          };
+          fire.sync(titleChanged);
+        }
+      };
+
+      PlacesUtils.observers.addListener(["page-title-changed"], listener);
+      return {
+        unregister() {
+          PlacesUtils.observers.removeListener(
+            ["page-title-changed"],
+            listener
+          );
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+  };
+
+  getAPI(context) {
+    return {
+      history: {
+        addUrl: function (details) {
+          let transition, date;
+          try {
+            transition = getTransitionType(details.transition);
+          } catch (error) {
+            return Promise.reject({ message: error.message });
+          }
+          if (details.visitTime) {
+            date = normalizeTime(details.visitTime);
+          }
+          let pageInfo = {
+            title: details.title,
+            url: details.url,
+            visits: [
+              {
+                transition,
+                date,
+              },
+            ],
+          };
+          try {
+            return PlacesUtils.history.insert(pageInfo).then(() => undefined);
+          } catch (error) {
+            return Promise.reject({ message: error.message });
+          }
+        },
+
+        deleteAll: function () {
+          return PlacesUtils.history.clear();
+        },
+
+        deleteRange: function (filter) {
+          let newFilter = {
+            beginDate: normalizeTime(filter.startTime),
+            endDate: normalizeTime(filter.endTime),
+          };
+          // History.removeVisitsByFilter returns a boolean, but our API should return nothing
+          return PlacesUtils.history
+            .removeVisitsByFilter(newFilter)
+            .then(() => undefined);
+        },
+
+        deleteUrl: function (details) {
+          let url = details.url;
+          // History.remove returns a boolean, but our API should return nothing
+          return PlacesUtils.history.remove(url).then(() => undefined);
+        },
+
+        search: function (query) {
+          let beginTime =
+            query.startTime == null
+              ? PlacesUtils.toPRTime(Date.now() - 24 * 60 * 60 * 1000)
+              : PlacesUtils.toPRTime(normalizeTime(query.startTime));
+          let endTime =
+            query.endTime == null
+              ? Number.MAX_VALUE
+              : PlacesUtils.toPRTime(normalizeTime(query.endTime));
+          if (beginTime > endTime) {
+            return Promise.reject({
+              message: "The startTime cannot be after the endTime",
+            });
+          }
+
+          let options = PlacesUtils.history.getNewQueryOptions();
+          options.includeHidden = true;
+          options.sortingMode = options.SORT_BY_DATE_DESCENDING;
+          options.maxResults = query.maxResults || 100;
+
+          let historyQuery = PlacesUtils.history.getNewQuery();
+          historyQuery.searchTerms = query.text;
+          historyQuery.beginTime = beginTime;
+          historyQuery.endTime = endTime;
+          return executeAsyncQuery(
+            historyQuery,
+            options,
+            convertRowToHistoryItem
+          );
+        },
+
+        getVisits: function (details) {
+          let url = details.url;
+          if (!url) {
+            return Promise.reject({
+              message: "A URL must be provided for getVisits",
+            });
+          }
+
+          let options = PlacesUtils.history.getNewQueryOptions();
+          options.includeHidden = true;
+          options.sortingMode = options.SORT_BY_DATE_DESCENDING;
+          options.resultType = options.RESULTS_AS_VISIT;
+
+          let historyQuery = PlacesUtils.history.getNewQuery();
+          historyQuery.uri = Services.io.newURI(url);
+          return executeAsyncQuery(
+            historyQuery,
+            options,
+            convertRowToVisitItem
+          );
+        },
+
+        onVisited: new EventManager({
+          context,
+          module: "history",
+          event: "onVisited",
+          extensionApi: this,
+        }).api(),
+
+        onVisitRemoved: new EventManager({
+          context,
+          module: "history",
+          event: "onVisitRemoved",
+          extensionApi: this,
+        }).api(),
+
+        onTitleChanged: new EventManager({
+          context,
+          module: "history",
+          event: "onTitleChanged",
+          extensionApi: this,
+        }).api(),
+      },
+    };
+  }
+};
diff --git a/browser/components/extensions/parent/ext-menus.js b/browser/components/extensions/parent/ext-menus.js
new file mode 100644
index 0000000000..74ce398b48
--- /dev/null
+++ b/browser/components/extensions/parent/ext-menus.js
@@ -0,0 +1,1471 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  PlacesUtils: "resource://gre/modules/PlacesUtils.sys.mjs",
+  PrivateBrowsingUtils: "resource://gre/modules/PrivateBrowsingUtils.sys.mjs",
+});
+
+var { DefaultMap, ExtensionError, parseMatchPatterns } = ExtensionUtils;
+
+var { ExtensionParent } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionParent.sys.mjs"
+);
+
+var { IconDetails, StartupCache } = ExtensionParent;
+
+const ACTION_MENU_TOP_LEVEL_LIMIT = 6;
+
+// Map[Extension -> Map[ID -> MenuItem]]
+// Note: we want to enumerate all the menu items so
+// this cannot be a weak map.
+var gMenuMap = new Map();
+
+// Map[Extension -> Map[ID -> MenuCreateProperties]]
+// The map object for each extension is a reference to the same
+// object in StartupCache.menus.  This provides a non-async
+// getter for that object.
+var gStartupCache = new Map();
+
+// Map[Extension -> MenuItem]
+var gRootItems = new Map();
+
+// Map[Extension -> ID[]]
+// Menu IDs that were eligible for being shown in the current menu.
+var gShownMenuItems = new DefaultMap(() => []);
+
+// Map[Extension -> Set[Contexts]]
+// A DefaultMap (keyed by extension) which keeps track of the
+// contexts with a subscribed onShown event listener.
+var gOnShownSubscribers = new DefaultMap(() => new Set());
+
+// If id is not specified for an item we use an integer.
+var gNextMenuItemID = 0;
+
+// Used to assign unique names to radio groups.
+var gNextRadioGroupID = 0;
+
+// The max length of a menu item's label.
+var gMaxLabelLength = 64;
+
+var gMenuBuilder = {
+  // When a new menu is opened, this function is called and
+  // we populate the |xulMenu| with all the items from extensions
+  // to be displayed. We always clear all the items again when
+  // popuphidden fires.
+  build(contextData) {
+    contextData = this.maybeOverrideContextData(contextData);
+    let xulMenu = contextData.menu;
+    xulMenu.addEventListener("popuphidden", this);
+    this.xulMenu = xulMenu;
+    for (let [, root] of gRootItems) {
+      this.createAndInsertTopLevelElements(root, contextData, null);
+    }
+    this.afterBuildingMenu(contextData);
+
+    if (
+      contextData.webExtContextData &&
+      !contextData.webExtContextData.showDefaults
+    ) {
+      // Wait until nsContextMenu.js has toggled the visibility of the default
+      // menu items before hiding the default items.
+      Promise.resolve().then(() => this.hideDefaultMenuItems());
+    }
+  },
+
+  maybeOverrideContextData(contextData) {
+    let { webExtContextData } = contextData;
+    if (!webExtContextData || !webExtContextData.overrideContext) {
+      return contextData;
+    }
+    let contextDataBase = {
+      menu: contextData.menu,
+      // eslint-disable-next-line no-use-before-define
+      originalViewType: getContextViewType(contextData),
+      originalViewUrl: contextData.inFrame
+        ? contextData.frameUrl
+        : contextData.pageUrl,
+      webExtContextData,
+    };
+    if (webExtContextData.overrideContext === "bookmark") {
+      return {
+        ...contextDataBase,
+        bookmarkId: webExtContextData.bookmarkId,
+        onBookmark: true,
+      };
+    }
+    if (webExtContextData.overrideContext === "tab") {
+      // TODO: Handle invalid tabs more gracefully (instead of throwing).
+      let tab = tabTracker.getTab(webExtContextData.tabId);
+      return {
+        ...contextDataBase,
+        tab,
+        pageUrl: tab.linkedBrowser.currentURI.spec,
+        onTab: true,
+      };
+    }
+    throw new Error(
+      `Unexpected overrideContext: ${webExtContextData.overrideContext}`
+    );
+  },
+
+  canAccessContext(extension, contextData) {
+    if (!extension.privateBrowsingAllowed) {
+      let nativeTab = contextData.tab;
+      if (
+        nativeTab &&
+        PrivateBrowsingUtils.isBrowserPrivate(nativeTab.linkedBrowser)
+      ) {
+        return false;
+      } else if (
+        PrivateBrowsingUtils.isWindowPrivate(contextData.menu.ownerGlobal)
+      ) {
+        return false;
+      }
+    }
+    return true;
+  },
+
+  createAndInsertTopLevelElements(root, contextData, nextSibling) {
+    let rootElements;
+    if (!this.canAccessContext(root.extension, contextData)) {
+      return;
+    }
+    if (
+      contextData.onAction ||
+      contextData.onBrowserAction ||
+      contextData.onPageAction
+    ) {
+      if (contextData.extension.id !== root.extension.id) {
+        return;
+      }
+      rootElements = this.buildTopLevelElements(
+        root,
+        contextData,
+        ACTION_MENU_TOP_LEVEL_LIMIT,
+        false
+      );
+
+      // Action menu items are prepended to the menu, followed by a separator.
+      nextSibling = nextSibling || this.xulMenu.firstElementChild;
+      if (rootElements.length && !this.itemsToCleanUp.has(nextSibling)) {
+        rootElements.push(
+          this.xulMenu.ownerDocument.createXULElement("menuseparator")
+        );
+      }
+    } else if (contextData.webExtContextData) {
+      let { extensionId, showDefaults, overrideContext } =
+        contextData.webExtContextData;
+      if (extensionId === root.extension.id) {
+        rootElements = this.buildTopLevelElements(
+          root,
+          contextData,
+          Infinity,
+          false
+        );
+        if (!nextSibling) {
+          // The extension menu should be rendered at the top. If we use
+          // a navigation group (on non-macOS), the extension menu should
+          // come after that to avoid styling issues.
+          if (AppConstants.platform == "macosx") {
+            nextSibling = this.xulMenu.firstElementChild;
+          } else {
+            nextSibling = this.xulMenu.querySelector(
+              ":scope > #context-sep-navigation + *"
+            );
+          }
+        }
+        if (
+          rootElements.length &&
+          showDefaults &&
+          !this.itemsToCleanUp.has(nextSibling)
+        ) {
+          rootElements.push(
+            this.xulMenu.ownerDocument.createXULElement("menuseparator")
+          );
+        }
+      } else if (!showDefaults && !overrideContext) {
+        // When the default menu items should be hidden, menu items from other
+        // extensions should be hidden too.
+        return;
+      }
+      // Fall through to show default extension menu items.
+    }
+    if (!rootElements) {
+      rootElements = this.buildTopLevelElements(root, contextData, 1, true);
+      if (
+        rootElements.length &&
+        !this.itemsToCleanUp.has(this.xulMenu.lastElementChild)
+      ) {
+        // All extension menu items are appended at the end.
+        // Prepend separator if this is the first extension menu item.
+        rootElements.unshift(
+          this.xulMenu.ownerDocument.createXULElement("menuseparator")
+        );
+      }
+    }
+
+    if (!rootElements.length) {
+      return;
+    }
+
+    if (nextSibling) {
+      nextSibling.before(...rootElements);
+    } else {
+      this.xulMenu.append(...rootElements);
+    }
+    for (let item of rootElements) {
+      this.itemsToCleanUp.add(item);
+    }
+  },
+
+  buildElementWithChildren(item, contextData) {
+    const element = this.buildSingleElement(item, contextData);
+    const children = this.buildChildren(item, contextData);
+    if (children.length) {
+      element.firstElementChild.append(...children);
+    }
+    return element;
+  },
+
+  buildChildren(item, contextData) {
+    let groupName;
+    let children = [];
+    for (let child of item.children) {
+      if (child.type == "radio" && !child.groupName) {
+        if (!groupName) {
+          groupName = `webext-radio-group-${gNextRadioGroupID++}`;
+        }
+        child.groupName = groupName;
+      } else {
+        groupName = null;
+      }
+
+      if (child.enabledForContext(contextData)) {
+        children.push(this.buildElementWithChildren(child, contextData));
+      }
+    }
+    return children;
+  },
+
+  buildTopLevelElements(root, contextData, maxCount, forceManifestIcons) {
+    let children = this.buildChildren(root, contextData);
+
+    // TODO: Fix bug 1492969 and remove this whole if block.
+    if (
+      children.length === 1 &&
+      maxCount === 1 &&
+      forceManifestIcons &&
+      AppConstants.platform === "linux" &&
+      children[0].getAttribute("type") === "checkbox"
+    ) {
+      // Keep single checkbox items in the submenu on Linux since
+      // the extension icon overlaps the checkbox otherwise.
+      maxCount = 0;
+    }
+
+    if (children.length > maxCount) {
+      // Move excess items into submenu.
+      let rootElement = this.buildSingleElement(root, contextData);
+      rootElement.setAttribute("ext-type", "top-level-menu");
+      rootElement.firstElementChild.append(...children.splice(maxCount - 1));
+      children.push(rootElement);
+    }
+
+    if (forceManifestIcons) {
+      for (let rootElement of children) {
+        // Display the extension icon on the root element.
+        if (
+          root.extension.manifest.icons &&
+          rootElement.getAttribute("type") !== "checkbox"
+        ) {
+          this.setMenuItemIcon(
+            rootElement,
+            root.extension,
+            contextData,
+            root.extension.manifest.icons
+          );
+        } else {
+          this.removeMenuItemIcon(rootElement);
+        }
+      }
+    }
+    return children;
+  },
+
+  buildSingleElement(item, contextData) {
+    let doc = contextData.menu.ownerDocument;
+    let element;
+    if (item.children.length) {
+      element = this.createMenuElement(doc, item);
+    } else if (item.type == "separator") {
+      element = doc.createXULElement("menuseparator");
+    } else {
+      element = doc.createXULElement("menuitem");
+    }
+
+    return this.customizeElement(element, item, contextData);
+  },
+
+  createMenuElement(doc, item) {
+    let element = doc.createXULElement("menu");
+    // Menu elements need to have a menupopup child for its menu items.
+    let menupopup = doc.createXULElement("menupopup");
+    element.appendChild(menupopup);
+    return element;
+  },
+
+  customizeElement(element, item, contextData) {
+    let label = item.title;
+    if (label) {
+      let accessKey;
+      label = label.replace(/&([\S\s]|$)/g, (_, nextChar, i) => {
+        if (nextChar === "&") {
+          return "&";
+        }
+        if (accessKey === undefined) {
+          if (nextChar === "%" && label.charAt(i + 2) === "s") {
+            accessKey = "";
+          } else {
+            accessKey = nextChar;
+          }
+        }
+        return nextChar;
+      });
+      element.setAttribute("accesskey", accessKey || "");
+
+      if (contextData.isTextSelected && label.indexOf("%s") > -1) {
+        let selection = contextData.selectionText.trim();
+        // The rendering engine will truncate the title if it's longer than 64 characters.
+        // But if it makes sense let's try truncate selection text only, to handle cases like
+        // 'look up "%s" in MyDictionary' more elegantly.
+
+        let codePointsToRemove = 0;
+
+        let selectionArray = Array.from(selection);
+
+        let completeLabelLength = label.length - 2 + selectionArray.length;
+        if (completeLabelLength > gMaxLabelLength) {
+          codePointsToRemove = completeLabelLength - gMaxLabelLength;
+        }
+
+        if (codePointsToRemove) {
+          let ellipsis = "\u2026";
+          try {
+            ellipsis = Services.prefs.getComplexValue(
+              "intl.ellipsis",
+              Ci.nsIPrefLocalizedString
+            ).data;
+          } catch (e) {}
+          codePointsToRemove += 1;
+          selection =
+            selectionArray.slice(0, -codePointsToRemove).join("") + ellipsis;
+        }
+
+        label = label.replace(/%s/g, selection);
+      }
+
+      element.setAttribute("label", label);
+    }
+
+    element.setAttribute("id", item.elementId);
+
+    if ("icons" in item) {
+      if (item.icons) {
+        this.setMenuItemIcon(element, item.extension, contextData, item.icons);
+      } else {
+        this.removeMenuItemIcon(element);
+      }
+    }
+
+    if (item.type == "checkbox") {
+      element.setAttribute("type", "checkbox");
+      if (item.checked) {
+        element.setAttribute("checked", "true");
+      }
+    } else if (item.type == "radio") {
+      element.setAttribute("type", "radio");
+      element.setAttribute("name", item.groupName);
+      if (item.checked) {
+        element.setAttribute("checked", "true");
+      }
+    }
+
+    if (!item.enabled) {
+      element.setAttribute("disabled", "true");
+    }
+
+    element.addEventListener(
+      "command",
+      event => {
+        if (event.target !== event.currentTarget) {
+          return;
+        }
+        const wasChecked = item.checked;
+        if (item.type == "checkbox") {
+          item.checked = !item.checked;
+        } else if (item.type == "radio") {
+          // Deselect all radio items in the current radio group.
+          for (let child of item.parent.children) {
+            if (child.type == "radio" && child.groupName == item.groupName) {
+              child.checked = false;
+            }
+          }
+          // Select the clicked radio item.
+          item.checked = true;
+        }
+
+        let { webExtContextData } = contextData;
+        if (
+          contextData.tab &&
+          // If the menu context was overridden by the extension, do not grant
+          // activeTab since the extension also controls the tabId.
+          (!webExtContextData ||
+            webExtContextData.extensionId !== item.extension.id)
+        ) {
+          item.tabManager.addActiveTabPermission(contextData.tab);
+        }
+
+        let info = item.getClickInfo(contextData, wasChecked);
+        info.modifiers = clickModifiersFromEvent(event);
+
+        info.button = event.button;
+
+        let _execute_action =
+          item.extension.manifestVersion < 3
+            ? "_execute_browser_action"
+            : "_execute_action";
+
+        // Allow menus to open various actions supported in webext prior
+        // to notifying onclicked.
+        let actionFor = {
+          [_execute_action]: global.browserActionFor,
+          _execute_page_action: global.pageActionFor,
+          _execute_sidebar_action: global.sidebarActionFor,
+        }[item.command];
+        if (actionFor) {
+          let win = event.target.ownerGlobal;
+          actionFor(item.extension).triggerAction(win);
+          return;
+        }
+
+        item.extension.emit(
+          "webext-menu-menuitem-click",
+          info,
+          contextData.tab
+        );
+      },
+      { once: true }
+    );
+
+    // Don't publish the ID of the root because the root element is
+    // auto-generated.
+    if (item.parent) {
+      gShownMenuItems.get(item.extension).push(item.id);
+    }
+
+    return element;
+  },
+
+  setMenuItemIcon(element, extension, contextData, icons) {
+    let parentWindow = contextData.menu.ownerGlobal;
+
+    let { icon } = IconDetails.getPreferredIcon(
+      icons,
+      extension,
+      16 * parentWindow.devicePixelRatio
+    );
+
+    // The extension icons in the manifest are not pre-resolved, since
+    // they're sometimes used by the add-on manager when the extension is
+    // not enabled, and its URLs are not resolvable.
+    let resolvedURL = extension.baseURI.resolve(icon);
+
+    if (element.localName == "menu") {
+      element.setAttribute("class", "menu-iconic");
+    } else if (element.localName == "menuitem") {
+      element.setAttribute("class", "menuitem-iconic");
+    }
+
+    element.setAttribute("image", resolvedURL);
+  },
+
+  // Undo changes from setMenuItemIcon.
+  removeMenuItemIcon(element) {
+    element.removeAttribute("class");
+    element.removeAttribute("image");
+  },
+
+  rebuildMenu(extension) {
+    let { contextData } = this;
+    if (!contextData) {
+      // This happens if the menu is not visible.
+      return;
+    }
+
+    // Find the group of existing top-level items (usually 0 or 1 items)
+    // and remember its position for when the new items are inserted.
+    let elementIdPrefix = `${makeWidgetId(extension.id)}-menuitem-`;
+    let nextSibling = null;
+    for (let item of this.itemsToCleanUp) {
+      if (item.id && item.id.startsWith(elementIdPrefix)) {
+        nextSibling = item.nextSibling;
+        item.remove();
+        this.itemsToCleanUp.delete(item);
+      }
+    }
+
+    let root = gRootItems.get(extension);
+    if (root) {
+      this.createAndInsertTopLevelElements(root, contextData, nextSibling);
+    }
+
+    this.xulMenu.showHideSeparators?.();
+  },
+
+  // This should be called once, after constructing the top-level menus, if any.
+  afterBuildingMenu(contextData) {
+    let dispatchOnShownEvent = extension => {
+      if (!this.canAccessContext(extension, contextData)) {
+        return;
+      }
+
+      // Note: gShownMenuItems is a DefaultMap, so .get(extension) causes the
+      // extension to be stored in the map even if there are currently no
+      // shown menu items. This ensures that the onHidden event can be fired
+      // when the menu is closed.
+      let menuIds = gShownMenuItems.get(extension);
+      extension.emit("webext-menu-shown", menuIds, contextData);
+    };
+
+    if (
+      contextData.onAction ||
+      contextData.onBrowserAction ||
+      contextData.onPageAction
+    ) {
+      dispatchOnShownEvent(contextData.extension);
+    } else {
+      for (const extension of gOnShownSubscribers.keys()) {
+        dispatchOnShownEvent(extension);
+      }
+    }
+
+    this.contextData = contextData;
+  },
+
+  hideDefaultMenuItems() {
+    for (let item of this.xulMenu.children) {
+      if (!this.itemsToCleanUp.has(item)) {
+        item.hidden = true;
+      }
+    }
+
+    if (this.xulMenu.showHideSeparators) {
+      this.xulMenu.showHideSeparators();
+    }
+  },
+
+  handleEvent(event) {
+    if (this.xulMenu != event.target || event.type != "popuphidden") {
+      return;
+    }
+
+    delete this.xulMenu;
+    delete this.contextData;
+
+    let target = event.target;
+    target.removeEventListener("popuphidden", this);
+    for (let item of this.itemsToCleanUp) {
+      item.remove();
+    }
+    this.itemsToCleanUp.clear();
+    for (let extension of gShownMenuItems.keys()) {
+      extension.emit("webext-menu-hidden");
+    }
+    gShownMenuItems.clear();
+  },
+
+  itemsToCleanUp: new Set(),
+};
+
+// Called from pageAction or browserAction popup.
+global.actionContextMenu = function (contextData) {
+  contextData.tab = tabTracker.activeTab;
+  contextData.pageUrl = contextData.tab.linkedBrowser.currentURI.spec;
+  gMenuBuilder.build(contextData);
+};
+
+const contextsMap = {
+  onAudio: "audio",
+  onEditable: "editable",
+  inFrame: "frame",
+  onImage: "image",
+  onLink: "link",
+  onPassword: "password",
+  isTextSelected: "selection",
+  onVideo: "video",
+
+  onBookmark: "bookmark",
+  onAction: "action",
+  onBrowserAction: "browser_action",
+  onPageAction: "page_action",
+  onTab: "tab",
+  inToolsMenu: "tools_menu",
+};
+
+const getMenuContexts = contextData => {
+  let contexts = new Set();
+
+  for (const [key, value] of Object.entries(contextsMap)) {
+    if (contextData[key]) {
+      contexts.add(value);
+    }
+  }
+
+  if (contexts.size === 0) {
+    contexts.add("page");
+  }
+
+  // New non-content contexts supported in Firefox are not part of "all".
+  if (
+    !contextData.onBookmark &&
+    !contextData.onTab &&
+    !contextData.inToolsMenu
+  ) {
+    contexts.add("all");
+  }
+
+  return contexts;
+};
+
+function getContextViewType(contextData) {
+  if ("originalViewType" in contextData) {
+    return contextData.originalViewType;
+  }
+  if (
+    contextData.webExtBrowserType === "popup" ||
+    contextData.webExtBrowserType === "sidebar"
+  ) {
+    return contextData.webExtBrowserType;
+  }
+  if (contextData.tab && contextData.menu.id === "contentAreaContextMenu") {
+    return "tab";
+  }
+  return undefined;
+}
+
+function addMenuEventInfo(info, contextData, extension, includeSensitiveData) {
+  info.viewType = getContextViewType(contextData);
+  if (contextData.onVideo) {
+    info.mediaType = "video";
+  } else if (contextData.onAudio) {
+    info.mediaType = "audio";
+  } else if (contextData.onImage) {
+    info.mediaType = "image";
+  }
+  if (contextData.frameId !== undefined) {
+    info.frameId = contextData.frameId;
+  }
+  if (contextData.onBookmark) {
+    info.bookmarkId = contextData.bookmarkId;
+  }
+  info.editable = contextData.onEditable || false;
+  if (includeSensitiveData) {
+    // menus.getTargetElement requires the "menus" permission, so do not set
+    // targetElementId for extensions with only the "contextMenus" permission.
+    if (contextData.timeStamp && extension.hasPermission("menus")) {
+      // Convert to integer, in case the DOMHighResTimeStamp has a fractional part.
+      info.targetElementId = Math.floor(contextData.timeStamp);
+    }
+    if (contextData.onLink) {
+      info.linkText = contextData.linkText;
+      info.linkUrl = contextData.linkUrl;
+    }
+    if (contextData.onAudio || contextData.onImage || contextData.onVideo) {
+      info.srcUrl = contextData.srcUrl;
+    }
+    if (!contextData.onBookmark) {
+      info.pageUrl = contextData.pageUrl;
+    }
+    if (contextData.inFrame) {
+      info.frameUrl = contextData.frameUrl;
+    }
+    if (contextData.isTextSelected) {
+      info.selectionText = contextData.selectionText;
+    }
+  }
+  // If the context was overridden, then frameUrl should be the URL of the
+  // document in which the menu was opened (instead of undefined, even if that
+  // document is not in a frame).
+  if (contextData.originalViewUrl) {
+    info.frameUrl = contextData.originalViewUrl;
+  }
+}
+
+class MenuItem {
+  constructor(extension, createProperties, isRoot = false) {
+    this.extension = extension;
+    this.children = [];
+    this.parent = null;
+    this.tabManager = extension.tabManager;
+
+    this.setDefaults();
+    this.setProps(createProperties);
+
+    if (!this.hasOwnProperty("_id")) {
+      this.id = gNextMenuItemID++;
+    }
+    // If the item is not the root and has no parent
+    // it must be a child of the root.
+    if (!isRoot && !this.parent) {
+      this.root.addChild(this);
+    }
+  }
+
+  static mergeProps(obj, properties) {
+    for (let propName in properties) {
+      if (properties[propName] === null) {
+        // Omitted optional argument.
+        continue;
+      }
+      obj[propName] = properties[propName];
+    }
+
+    if ("icons" in properties && properties.icons === null && obj.icons) {
+      obj.icons = null;
+    }
+  }
+
+  setProps(createProperties) {
+    MenuItem.mergeProps(this, createProperties);
+
+    if (createProperties.documentUrlPatterns != null) {
+      this.documentUrlMatchPattern = parseMatchPatterns(
+        this.documentUrlPatterns,
+        {
+          restrictSchemes: this.extension.restrictSchemes,
+        }
+      );
+    }
+
+    if (createProperties.targetUrlPatterns != null) {
+      this.targetUrlMatchPattern = parseMatchPatterns(this.targetUrlPatterns, {
+        // restrictSchemes default to false when matching links instead of pages
+        // (see Bug 1280370 for a rationale).
+        restrictSchemes: false,
+      });
+    }
+
+    // If a child MenuItem does not specify any contexts, then it should
+    // inherit the contexts specified from its parent.
+    if (createProperties.parentId && !createProperties.contexts) {
+      this.contexts = this.parent.contexts;
+    }
+  }
+
+  setDefaults() {
+    this.setProps({
+      type: "normal",
+      checked: false,
+      contexts: ["all"],
+      enabled: true,
+      visible: true,
+    });
+  }
+
+  set id(id) {
+    if (this.hasOwnProperty("_id")) {
+      throw new ExtensionError("ID of a MenuItem cannot be changed");
+    }
+    let isIdUsed = gMenuMap.get(this.extension).has(id);
+    if (isIdUsed) {
+      throw new ExtensionError(`ID already exists: ${id}`);
+    }
+    this._id = id;
+  }
+
+  get id() {
+    return this._id;
+  }
+
+  get elementId() {
+    let id = this.id;
+    // If the ID is an integer, it is auto-generated and globally unique.
+    // If the ID is a string, it is only unique within one extension and the
+    // ID needs to be concatenated with the extension ID.
+    if (typeof id !== "number") {
+      // To avoid collisions with numeric IDs, add a prefix to string IDs.
+      id = `_${id}`;
+    }
+    return `${makeWidgetId(this.extension.id)}-menuitem-${id}`;
+  }
+
+  ensureValidParentId(parentId) {
+    if (parentId === undefined) {
+      return;
+    }
+    let menuMap = gMenuMap.get(this.extension);
+    if (!menuMap.has(parentId)) {
+      throw new ExtensionError(
+        `Could not find any MenuItem with id: ${parentId}`
+      );
+    }
+    for (let item = menuMap.get(parentId); item; item = item.parent) {
+      if (item === this) {
+        throw new ExtensionError(
+          "MenuItem cannot be an ancestor (or self) of its new parent."
+        );
+      }
+    }
+  }
+
+  /**
+   * When updating menu properties we need to ensure parents exist
+   * in the cache map before children.  That allows the menus to be
+   * created in the correct sequence on startup.  This reparents the
+   * tree starting from this instance of MenuItem.
+   */
+  reparentInCache() {
+    let { id, extension } = this;
+    let cachedMap = gStartupCache.get(extension);
+    let createProperties = cachedMap.get(id);
+    cachedMap.delete(id);
+    cachedMap.set(id, createProperties);
+
+    for (let child of this.children) {
+      child.reparentInCache();
+    }
+  }
+
+  set parentId(parentId) {
+    this.ensureValidParentId(parentId);
+
+    if (this.parent) {
+      this.parent.detachChild(this);
+    }
+
+    if (parentId === undefined) {
+      this.root.addChild(this);
+    } else {
+      let menuMap = gMenuMap.get(this.extension);
+      menuMap.get(parentId).addChild(this);
+    }
+  }
+
+  get parentId() {
+    return this.parent ? this.parent.id : undefined;
+  }
+
+  addChild(child) {
+    if (child.parent) {
+      throw new Error("Child MenuItem already has a parent.");
+    }
+    this.children.push(child);
+    child.parent = this;
+  }
+
+  detachChild(child) {
+    let idx = this.children.indexOf(child);
+    if (idx < 0) {
+      throw new Error("Child MenuItem not found, it cannot be removed.");
+    }
+    this.children.splice(idx, 1);
+    child.parent = null;
+  }
+
+  get root() {
+    let extension = this.extension;
+    if (!gRootItems.has(extension)) {
+      let root = new MenuItem(
+        extension,
+        { title: extension.name },
+        /* isRoot = */ true
+      );
+      gRootItems.set(extension, root);
+    }
+
+    return gRootItems.get(extension);
+  }
+
+  remove() {
+    if (this.parent) {
+      this.parent.detachChild(this);
+    }
+    let children = this.children.slice(0);
+    for (let child of children) {
+      child.remove();
+    }
+
+    let menuMap = gMenuMap.get(this.extension);
+    menuMap.delete(this.id);
+    // Menu items are saved if !extension.persistentBackground.
+    if (gStartupCache.get(this.extension)?.delete(this.id)) {
+      StartupCache.save();
+    }
+    if (this.root == this) {
+      gRootItems.delete(this.extension);
+    }
+  }
+
+  getClickInfo(contextData, wasChecked) {
+    let info = {
+      menuItemId: this.id,
+    };
+    if (this.parent) {
+      info.parentMenuItemId = this.parentId;
+    }
+
+    addMenuEventInfo(info, contextData, this.extension, true);
+
+    if (this.type === "checkbox" || this.type === "radio") {
+      info.checked = this.checked;
+      info.wasChecked = wasChecked;
+    }
+
+    return info;
+  }
+
+  enabledForContext(contextData) {
+    if (!this.visible) {
+      return false;
+    }
+    let contexts = getMenuContexts(contextData);
+    if (!this.contexts.some(n => contexts.has(n))) {
+      return false;
+    }
+
+    if (
+      this.viewTypes &&
+      !this.viewTypes.includes(getContextViewType(contextData))
+    ) {
+      return false;
+    }
+
+    let docPattern = this.documentUrlMatchPattern;
+    // When viewTypes is specified, the menu item is expected to be restricted
+    // to documents. So let documentUrlPatterns always apply to the URL of the
+    // document in which the menu was opened. When maybeOverrideContextData
+    // changes the context, contextData.pageUrl does not reflect that URL any
+    // more, so use contextData.originalViewUrl instead.
+    if (docPattern && this.viewTypes && contextData.originalViewUrl) {
+      if (
+        !docPattern.matches(Services.io.newURI(contextData.originalViewUrl))
+      ) {
+        return false;
+      }
+      docPattern = null; // Null it so that it won't be used with pageURI below.
+    }
+
+    if (contextData.onBookmark) {
+      return this.extension.hasPermission("bookmarks");
+    }
+
+    let pageURI = Services.io.newURI(
+      contextData[contextData.inFrame ? "frameUrl" : "pageUrl"]
+    );
+    if (docPattern && !docPattern.matches(pageURI)) {
+      return false;
+    }
+
+    let targetPattern = this.targetUrlMatchPattern;
+    if (targetPattern) {
+      let targetURIs = [];
+      if (contextData.onImage || contextData.onAudio || contextData.onVideo) {
+        // TODO: double check if srcUrl is always set when we need it
+        targetURIs.push(Services.io.newURI(contextData.srcUrl));
+      }
+      // contextData.linkURI may be null despite contextData.onLink, when
+      // contextData.linkUrl is an invalid URL.
+      if (contextData.onLink && contextData.linkURI) {
+        targetURIs.push(contextData.linkURI);
+      }
+      if (!targetURIs.some(targetURI => targetPattern.matches(targetURI))) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+}
+
+// windowTracker only looks as browser windows, but we're also interested in
+// the Library window.  Helper for menuTracker below.
+const libraryTracker = {
+  libraryWindowType: "Places:Organizer",
+
+  isLibraryWindow(window) {
+    let winType = window.document.documentElement.getAttribute("windowtype");
+    return winType === this.libraryWindowType;
+  },
+
+  init(listener) {
+    this._listener = listener;
+    Services.ww.registerNotification(this);
+
+    // See WindowTrackerBase#*browserWindows in ext-tabs-base.js for why we
+    // can't use the enumerator's windowtype filter.
+    for (let window of Services.wm.getEnumerator("")) {
+      if (window.document.readyState === "complete") {
+        if (this.isLibraryWindow(window)) {
+          this.notify(window);
+        }
+      } else {
+        window.addEventListener("load", this, { once: true });
+      }
+    }
+  },
+
+  // cleanupWindow is called on any library window that's open.
+  uninit(cleanupWindow) {
+    Services.ww.unregisterNotification(this);
+
+    for (let window of Services.wm.getEnumerator("")) {
+      window.removeEventListener("load", this);
+      try {
+        if (this.isLibraryWindow(window)) {
+          cleanupWindow(window);
+        }
+      } catch (e) {
+        Cu.reportError(e);
+      }
+    }
+  },
+
+  // Gets notifications from Services.ww.registerNotification.
+  // Defer actually doing anything until the window's loaded, though.
+  observe(window, topic) {
+    if (topic === "domwindowopened") {
+      window.addEventListener("load", this, { once: true });
+    }
+  },
+
+  // Gets the load event for new windows(registered in observe()).
+  handleEvent(event) {
+    let window = event.target.defaultView;
+    if (this.isLibraryWindow(window)) {
+      this.notify(window);
+    }
+  },
+
+  notify(window) {
+    try {
+      this._listener.call(null, window);
+    } catch (e) {
+      Cu.reportError(e);
+    }
+  },
+};
+
+// While any extensions are active, this Tracker registers to observe/listen
+// for menu events from both Tools and context menus, both content and chrome.
+const menuTracker = {
+  menuIds: ["placesContext", "menu_ToolsPopup", "tabContextMenu"],
+
+  register() {
+    Services.obs.addObserver(this, "on-build-contextmenu");
+    for (const window of windowTracker.browserWindows()) {
+      this.onWindowOpen(window);
+    }
+    windowTracker.addOpenListener(this.onWindowOpen);
+    libraryTracker.init(this.onLibraryOpen);
+  },
+
+  unregister() {
+    Services.obs.removeObserver(this, "on-build-contextmenu");
+    for (const window of windowTracker.browserWindows()) {
+      this.cleanupWindow(window);
+    }
+    windowTracker.removeOpenListener(this.onWindowOpen);
+    libraryTracker.uninit(this.cleanupLibrary);
+  },
+
+  observe(subject, topic, data) {
+    subject = subject.wrappedJSObject;
+    gMenuBuilder.build(subject);
+  },
+
+  async onWindowOpen(window) {
+    for (const id of menuTracker.menuIds) {
+      const menu = window.document.getElementById(id);
+      menu.addEventListener("popupshowing", menuTracker);
+    }
+
+    const sidebarHeader = window.document.getElementById(
+      "sidebar-switcher-target"
+    );
+    sidebarHeader.addEventListener("SidebarShown", menuTracker.onSidebarShown);
+
+    await window.SidebarUI.promiseInitialized;
+
+    if (
+      !window.closed &&
+      window.SidebarUI.currentID === "viewBookmarksSidebar"
+    ) {
+      menuTracker.onSidebarShown({ currentTarget: sidebarHeader });
+    }
+  },
+
+  cleanupWindow(window) {
+    for (const id of this.menuIds) {
+      const menu = window.document.getElementById(id);
+      menu.removeEventListener("popupshowing", this);
+    }
+
+    const sidebarHeader = window.document.getElementById(
+      "sidebar-switcher-target"
+    );
+    sidebarHeader.removeEventListener("SidebarShown", this.onSidebarShown);
+
+    if (window.SidebarUI.currentID === "viewBookmarksSidebar") {
+      let sidebarBrowser = window.SidebarUI.browser;
+      sidebarBrowser.removeEventListener("load", this.onSidebarShown);
+      const menu =
+        sidebarBrowser.contentDocument.getElementById("placesContext");
+      menu.removeEventListener("popupshowing", this.onBookmarksContextMenu);
+    }
+  },
+
+  onSidebarShown(event) {
+    // The event target is an element in a browser window, so |window| will be
+    // the browser window that contains the sidebar.
+    const window = event.currentTarget.ownerGlobal;
+    if (window.SidebarUI.currentID === "viewBookmarksSidebar") {
+      let sidebarBrowser = window.SidebarUI.browser;
+      if (sidebarBrowser.contentDocument.readyState !== "complete") {
+        // SidebarUI.currentID may be updated before the bookmark sidebar's
+        // document has finished loading. This sometimes happens when the
+        // sidebar is automatically shown when a new window is opened.
+        sidebarBrowser.addEventListener("load", menuTracker.onSidebarShown, {
+          once: true,
+        });
+        return;
+      }
+      const menu =
+        sidebarBrowser.contentDocument.getElementById("placesContext");
+      menu.addEventListener("popupshowing", menuTracker.onBookmarksContextMenu);
+    }
+  },
+
+  onLibraryOpen(window) {
+    const menu = window.document.getElementById("placesContext");
+    menu.addEventListener("popupshowing", menuTracker.onBookmarksContextMenu);
+  },
+
+  cleanupLibrary(window) {
+    const menu = window.document.getElementById("placesContext");
+    menu.removeEventListener(
+      "popupshowing",
+      menuTracker.onBookmarksContextMenu
+    );
+  },
+
+  handleEvent(event) {
+    const menu = event.target;
+
+    if (menu.id === "placesContext") {
+      const trigger = menu.triggerNode;
+      if (!trigger._placesNode?.bookmarkGuid) {
+        return;
+      }
+
+      gMenuBuilder.build({
+        menu,
+        bookmarkId: trigger._placesNode.bookmarkGuid,
+        onBookmark: true,
+      });
+    }
+    if (menu.id === "menu_ToolsPopup") {
+      const tab = tabTracker.activeTab;
+      const pageUrl = tab.linkedBrowser.currentURI.spec;
+      gMenuBuilder.build({ menu, tab, pageUrl, inToolsMenu: true });
+    }
+    if (menu.id === "tabContextMenu") {
+      const tab = menu.ownerGlobal.TabContextMenu.contextTab;
+      const pageUrl = tab.linkedBrowser.currentURI.spec;
+      gMenuBuilder.build({ menu, tab, pageUrl, onTab: true });
+    }
+  },
+
+  onBookmarksContextMenu(event) {
+    const menu = event.target;
+    const tree = menu.triggerNode.parentElement;
+    const cell = tree.getCellAt(event.x, event.y);
+    const node = tree.view.nodeForTreeIndex(cell.row);
+    const bookmarkId = node && PlacesUtils.getConcreteItemGuid(node);
+
+    if (!bookmarkId || PlacesUtils.isVirtualLeftPaneItem(bookmarkId)) {
+      return;
+    }
+
+    gMenuBuilder.build({ menu, bookmarkId, onBookmark: true });
+  },
+};
+
+this.menusInternal = class extends ExtensionAPIPersistent {
+  constructor(extension) {
+    super(extension);
+
+    if (!gMenuMap.size) {
+      menuTracker.register();
+    }
+    gMenuMap.set(extension, new Map());
+  }
+
+  restoreFromCache() {
+    let { extension } = this;
+    // ensure extension has not shutdown
+    if (!this.extension) {
+      return;
+    }
+    for (let createProperties of gStartupCache.get(extension).values()) {
+      // The order of menu creation is significant, see reparentInCache.
+      let menuItem = new MenuItem(extension, createProperties);
+      gMenuMap.get(extension).set(menuItem.id, menuItem);
+    }
+    // Used for testing
+    extension.emit("webext-menus-created", gMenuMap.get(extension));
+  }
+
+  async onStartup() {
+    let { extension } = this;
+    if (extension.persistentBackground) {
+      return;
+    }
+    // Using the map retains insertion order.
+    let cachedMenus = await StartupCache.menus.get(extension.id, () => {
+      return new Map();
+    });
+    gStartupCache.set(extension, cachedMenus);
+    if (!cachedMenus.size) {
+      return;
+    }
+
+    this.restoreFromCache();
+  }
+
+  onShutdown() {
+    let { extension } = this;
+
+    if (gMenuMap.has(extension)) {
+      gMenuMap.delete(extension);
+      gRootItems.delete(extension);
+      gShownMenuItems.delete(extension);
+      gStartupCache.delete(extension);
+      gOnShownSubscribers.delete(extension);
+      if (!gMenuMap.size) {
+        menuTracker.unregister();
+      }
+    }
+  }
+
+  PERSISTENT_EVENTS = {
+    onShown({ fire }) {
+      let { extension } = this;
+      let listener = (event, menuIds, contextData) => {
+        let info = {
+          menuIds,
+          contexts: Array.from(getMenuContexts(contextData)),
+        };
+
+        let nativeTab = contextData.tab;
+
+        // The menus.onShown event is fired before the user has consciously
+        // interacted with an extension, so we require permissions before
+        // exposing sensitive contextual data.
+        let contextUrl = contextData.inFrame
+          ? contextData.frameUrl
+          : contextData.pageUrl;
+        let includeSensitiveData =
+          (nativeTab &&
+            extension.tabManager.hasActiveTabPermission(nativeTab)) ||
+          (contextUrl && extension.allowedOrigins.matches(contextUrl));
+
+        addMenuEventInfo(info, contextData, extension, includeSensitiveData);
+
+        let tab = nativeTab && extension.tabManager.convert(nativeTab);
+        fire.sync(info, tab);
+      };
+      gOnShownSubscribers.get(extension).add(listener);
+      extension.on("webext-menu-shown", listener);
+      return {
+        unregister() {
+          const listeners = gOnShownSubscribers.get(extension);
+          listeners.delete(listener);
+          if (listeners.size === 0) {
+            gOnShownSubscribers.delete(extension);
+          }
+          extension.off("webext-menu-shown", listener);
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+    onHidden({ fire }) {
+      let { extension } = this;
+      let listener = () => {
+        fire.sync();
+      };
+      extension.on("webext-menu-hidden", listener);
+      return {
+        unregister() {
+          extension.off("webext-menu-hidden", listener);
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+    onClicked({ context, fire }) {
+      let { extension } = this;
+      let listener = async (event, info, nativeTab) => {
+        let { linkedBrowser } = nativeTab || tabTracker.activeTab;
+        let tab = nativeTab && extension.tabManager.convert(nativeTab);
+        if (fire.wakeup) {
+          // force the wakeup, thus the call to convert to get the context.
+          await fire.wakeup();
+          // If while waiting the tab disappeared we bail out.
+          if (
+            !linkedBrowser.ownerGlobal.gBrowser.getTabForBrowser(linkedBrowser)
+          ) {
+            Cu.reportError(
+              `menus.onClicked: target tab closed during background startup.`
+            );
+            return;
+          }
+        }
+        context.withPendingBrowser(linkedBrowser, () => fire.sync(info, tab));
+      };
+
+      extension.on("webext-menu-menuitem-click", listener);
+      return {
+        unregister() {
+          extension.off("webext-menu-menuitem-click", listener);
+        },
+        convert(_fire, _context) {
+          fire = _fire;
+          context = _context;
+        },
+      };
+    },
+  };
+
+  getAPI(context) {
+    let { extension } = context;
+
+    const menus = {
+      refresh() {
+        gMenuBuilder.rebuildMenu(extension);
+      },
+
+      onShown: new EventManager({
+        context,
+        module: "menusInternal",
+        event: "onShown",
+        name: "menus.onShown",
+        extensionApi: this,
+      }).api(),
+      onHidden: new EventManager({
+        context,
+        module: "menusInternal",
+        event: "onHidden",
+        name: "menus.onHidden",
+        extensionApi: this,
+      }).api(),
+    };
+
+    return {
+      contextMenus: menus,
+      menus,
+      menusInternal: {
+        create(createProperties) {
+          // event pages require id
+          if (!extension.persistentBackground) {
+            if (!createProperties.id) {
+              throw new ExtensionError(
+                "menus.create requires an id for non-persistent background scripts."
+              );
+            }
+            if (gMenuMap.get(extension).has(createProperties.id)) {
+              throw new ExtensionError(
+                `The menu id ${createProperties.id} already exists in menus.create.`
+              );
+            }
+          }
+
+          // Note that the id is required by the schema. If the addon did not set
+          // it, the implementation of menus.create in the child will add it for
+          // extensions with persistent backgrounds, but not otherwise.
+          let menuItem = new MenuItem(extension, createProperties);
+          gMenuMap.get(extension).set(menuItem.id, menuItem);
+          if (!extension.persistentBackground) {
+            // Only cache properties that are necessary.
+            let cached = {};
+            MenuItem.mergeProps(cached, createProperties);
+            gStartupCache.get(extension).set(menuItem.id, cached);
+            StartupCache.save();
+          }
+        },
+
+        update(id, updateProperties) {
+          let menuItem = gMenuMap.get(extension).get(id);
+          if (!menuItem) {
+            return;
+          }
+          menuItem.setProps(updateProperties);
+
+          // Update the startup cache for non-persistent extensions.
+          if (extension.persistentBackground) {
+            return;
+          }
+
+          let cached = gStartupCache.get(extension).get(id);
+          let reparent =
+            updateProperties.parentId != null &&
+            cached.parentId != updateProperties.parentId;
+          MenuItem.mergeProps(cached, updateProperties);
+          if (reparent) {
+            // The order of menu creation is significant, see reparentInCache.
+            menuItem.reparentInCache();
+          }
+          StartupCache.save();
+        },
+
+        remove(id) {
+          let menuItem = gMenuMap.get(extension).get(id);
+          if (menuItem) {
+            menuItem.remove();
+          }
+        },
+
+        removeAll() {
+          let root = gRootItems.get(extension);
+          if (root) {
+            root.remove();
+          }
+          // Should be empty, just extra assurance.
+          if (!extension.persistentBackground) {
+            let cached = gStartupCache.get(extension);
+            if (cached.size) {
+              cached.clear();
+              StartupCache.save();
+            }
+          }
+        },
+
+        onClicked: new EventManager({
+          context,
+          module: "menusInternal",
+          event: "onClicked",
+          name: "menus.onClicked",
+          extensionApi: this,
+        }).api(),
+      },
+    };
+  }
+};
diff --git a/browser/components/extensions/parent/ext-normandyAddonStudy.js b/browser/components/extensions/parent/ext-normandyAddonStudy.js
new file mode 100644
index 0000000000..0fcca4c678
--- /dev/null
+++ b/browser/components/extensions/parent/ext-normandyAddonStudy.js
@@ -0,0 +1,84 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { AddonStudies } = ChromeUtils.importESModule(
+  "resource://normandy/lib/AddonStudies.sys.mjs"
+);
+const { ClientID } = ChromeUtils.importESModule(
+  "resource://gre/modules/ClientID.sys.mjs"
+);
+
+ChromeUtils.defineESModuleGetters(this, {
+  AddonManager: "resource://gre/modules/AddonManager.sys.mjs",
+});
+
+this.normandyAddonStudy = class extends ExtensionAPI {
+  getAPI(context) {
+    let { extension } = context;
+
+    return {
+      normandyAddonStudy: {
+        /**
+         * Returns a study object for the current study.
+         *
+         * @returns {Study}
+         */
+        async getStudy() {
+          const studies = await AddonStudies.getAll();
+          return studies.find(study => study.addonId === extension.id);
+        },
+
+        /**
+         * Marks the study as ended and then uninstalls the addon.
+         *
+         * @param {string} reason Why the study is ending
+         */
+        async endStudy(reason) {
+          const study = await this.getStudy();
+
+          // Mark the study as ended
+          await AddonStudies.markAsEnded(study, reason);
+
+          // Uninstall the addon
+          const addon = await AddonManager.getAddonByID(study.addonId);
+          if (addon) {
+            await addon.uninstall();
+          }
+        },
+
+        /**
+         * Returns an object with metadata about the client which may
+         * be required for constructing survey URLs.
+         *
+         * @returns {object}
+         */
+        async getClientMetadata() {
+          return {
+            updateChannel: Services.appinfo.defaultUpdateChannel,
+            fxVersion: Services.appinfo.version,
+            clientID: await ClientID.getClientID(),
+          };
+        },
+
+        onUnenroll: new EventManager({
+          context,
+          name: "normandyAddonStudy.onUnenroll",
+          register: fire => {
+            const listener = async reason => {
+              await fire.async(reason);
+            };
+
+            AddonStudies.addUnenrollListener(extension.id, listener);
+
+            return () => {
+              AddonStudies.removeUnenrollListener(extension.id, listener);
+            };
+          },
+        }).api(),
+      },
+    };
+  }
+};
diff --git a/browser/components/extensions/parent/ext-omnibox.js b/browser/components/extensions/parent/ext-omnibox.js
new file mode 100644
index 0000000000..363db67325
--- /dev/null
+++ b/browser/components/extensions/parent/ext-omnibox.js
@@ -0,0 +1,177 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionSearchHandler:
+    "resource://gre/modules/ExtensionSearchHandler.sys.mjs",
+});
+
+this.omnibox = class extends ExtensionAPIPersistent {
+  PERSISTENT_EVENTS = {
+    onInputStarted({ fire }) {
+      let { extension } = this;
+      let listener = eventName => {
+        fire.sync();
+      };
+      extension.on(ExtensionSearchHandler.MSG_INPUT_STARTED, listener);
+      return {
+        unregister() {
+          extension.off(ExtensionSearchHandler.MSG_INPUT_STARTED, listener);
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+    onInputCancelled({ fire }) {
+      let { extension } = this;
+      let listener = eventName => {
+        fire.sync();
+      };
+      extension.on(ExtensionSearchHandler.MSG_INPUT_CANCELLED, listener);
+      return {
+        unregister() {
+          extension.off(ExtensionSearchHandler.MSG_INPUT_CANCELLED, listener);
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+    onInputEntered({ fire }) {
+      let { extension } = this;
+      let listener = (eventName, text, disposition) => {
+        fire.sync(text, disposition);
+      };
+      extension.on(ExtensionSearchHandler.MSG_INPUT_ENTERED, listener);
+      return {
+        unregister() {
+          extension.off(ExtensionSearchHandler.MSG_INPUT_ENTERED, listener);
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+    onInputChanged({ fire }) {
+      let { extension } = this;
+      let listener = (eventName, text, id) => {
+        fire.sync(text, id);
+      };
+      extension.on(ExtensionSearchHandler.MSG_INPUT_CHANGED, listener);
+      return {
+        unregister() {
+          extension.off(ExtensionSearchHandler.MSG_INPUT_CHANGED, listener);
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+    onDeleteSuggestion({ fire }) {
+      let { extension } = this;
+      let listener = (eventName, text) => {
+        fire.sync(text);
+      };
+      extension.on(ExtensionSearchHandler.MSG_INPUT_DELETED, listener);
+      return {
+        unregister() {
+          extension.off(ExtensionSearchHandler.MSG_INPUT_DELETED, listener);
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+  };
+
+  onManifestEntry(entryName) {
+    let { extension } = this;
+    let { manifest } = extension;
+
+    let keyword = manifest.omnibox.keyword;
+    try {
+      // This will throw if the keyword is already registered.
+      ExtensionSearchHandler.registerKeyword(keyword, extension);
+      this.keyword = keyword;
+    } catch (e) {
+      extension.manifestError(e.message);
+    }
+  }
+
+  onShutdown() {
+    ExtensionSearchHandler.unregisterKeyword(this.keyword);
+  }
+
+  getAPI(context) {
+    return {
+      omnibox: {
+        setDefaultSuggestion: suggestion => {
+          try {
+            // This will throw if the keyword failed to register.
+            ExtensionSearchHandler.setDefaultSuggestion(
+              this.keyword,
+              suggestion
+            );
+          } catch (e) {
+            return Promise.reject(e.message);
+          }
+        },
+
+        onInputStarted: new EventManager({
+          context,
+          module: "omnibox",
+          event: "onInputStarted",
+          extensionApi: this,
+        }).api(),
+
+        onInputCancelled: new EventManager({
+          context,
+          module: "omnibox",
+          event: "onInputCancelled",
+          extensionApi: this,
+        }).api(),
+
+        onInputEntered: new EventManager({
+          context,
+          module: "omnibox",
+          event: "onInputEntered",
+          extensionApi: this,
+        }).api(),
+
+        onInputChanged: new EventManager({
+          context,
+          module: "omnibox",
+          event: "onInputChanged",
+          extensionApi: this,
+        }).api(),
+
+        onDeleteSuggestion: new EventManager({
+          context,
+          module: "omnibox",
+          event: "onDeleteSuggestion",
+          extensionApi: this,
+        }).api(),
+
+        // Internal APIs.
+        addSuggestions: (id, suggestions) => {
+          try {
+            ExtensionSearchHandler.addSuggestions(
+              this.keyword,
+              id,
+              suggestions
+            );
+          } catch (e) {
+            // Silently fail because the extension developer can not know for sure if the user
+            // has already invalidated the callback when asynchronously providing suggestions.
+          }
+        },
+      },
+    };
+  }
+};
diff --git a/browser/components/extensions/parent/ext-pageAction.js b/browser/components/extensions/parent/ext-pageAction.js
new file mode 100644
index 0000000000..bfd8d14fd2
--- /dev/null
+++ b/browser/components/extensions/parent/ext-pageAction.js
@@ -0,0 +1,391 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionTelemetry: "resource://gre/modules/ExtensionTelemetry.sys.mjs",
+  PanelPopup: "resource:///modules/ExtensionPopups.sys.mjs",
+});
+ChromeUtils.defineModuleGetter(
+  this,
+  "PageActions",
+  "resource:///modules/PageActions.jsm"
+);
+ChromeUtils.defineModuleGetter(
+  this,
+  "BrowserUsageTelemetry",
+  "resource:///modules/BrowserUsageTelemetry.jsm"
+);
+
+var { DefaultWeakMap } = ExtensionUtils;
+
+var { ExtensionParent } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionParent.sys.mjs"
+);
+var { PageActionBase } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionActions.sys.mjs"
+);
+
+// WeakMap[Extension -> PageAction]
+let pageActionMap = new WeakMap();
+
+class PageAction extends PageActionBase {
+  constructor(extension, buttonDelegate) {
+    let tabContext = new TabContext(tab => this.getContextData(null));
+    super(tabContext, extension);
+    this.buttonDelegate = buttonDelegate;
+  }
+
+  updateOnChange(target) {
+    this.buttonDelegate.updateButton(target.ownerGlobal);
+  }
+
+  dispatchClick(tab, clickInfo) {
+    this.buttonDelegate.emit("click", tab, clickInfo);
+  }
+
+  getTab(tabId) {
+    if (tabId !== null) {
+      return tabTracker.getTab(tabId);
+    }
+    return null;
+  }
+}
+
+this.pageAction = class extends ExtensionAPIPersistent {
+  static for(extension) {
+    return pageActionMap.get(extension);
+  }
+
+  static onUpdate(id, manifest) {
+    if (!("page_action" in manifest)) {
+      // If the new version has no page action then mark this widget as hidden
+      // in the telemetry. If it is already marked hidden then this will do
+      // nothing.
+      BrowserUsageTelemetry.recordWidgetChange(makeWidgetId(id), null, "addon");
+    }
+  }
+
+  static onDisable(id) {
+    BrowserUsageTelemetry.recordWidgetChange(makeWidgetId(id), null, "addon");
+  }
+
+  static onUninstall(id) {
+    // If the telemetry already has this widget as hidden then this will not
+    // record anything.
+    BrowserUsageTelemetry.recordWidgetChange(makeWidgetId(id), null, "addon");
+  }
+
+  async onManifestEntry(entryName) {
+    let { extension } = this;
+    let options = extension.manifest.page_action;
+
+    this.action = new PageAction(extension, this);
+    await this.action.loadIconData();
+
+    let widgetId = makeWidgetId(extension.id);
+    this.id = widgetId + "-page-action";
+
+    this.tabManager = extension.tabManager;
+
+    this.browserStyle = options.browser_style;
+
+    pageActionMap.set(extension, this);
+
+    this.lastValues = new DefaultWeakMap(() => ({}));
+
+    if (!this.browserPageAction) {
+      let onPlacedHandler = (buttonNode, isPanel) => {
+        // eslint-disable-next-line mozilla/balanced-listeners
+        buttonNode.addEventListener("auxclick", event => {
+          if (event.button !== 1 || event.target.disabled) {
+            return;
+          }
+
+          // The panel is not automatically closed when middle-clicked.
+          if (isPanel) {
+            buttonNode.closest("#pageActionPanel").hidePopup();
+          }
+          let window = event.target.ownerGlobal;
+          let tab = window.gBrowser.selectedTab;
+          this.tabManager.addActiveTabPermission(tab);
+          this.action.dispatchClick(tab, {
+            button: event.button,
+            modifiers: clickModifiersFromEvent(event),
+          });
+        });
+      };
+
+      this.browserPageAction = PageActions.addAction(
+        new PageActions.Action({
+          id: widgetId,
+          extensionID: extension.id,
+          title: this.action.getProperty(null, "title"),
+          iconURL: this.action.getProperty(null, "icon"),
+          pinnedToUrlbar: this.action.getPinned(),
+          disabled: !this.action.getProperty(null, "enabled"),
+          onCommand: (event, buttonNode) => {
+            this.handleClick(event.target.ownerGlobal, {
+              button: event.button || 0,
+              modifiers: clickModifiersFromEvent(event),
+            });
+          },
+          onBeforePlacedInWindow: browserWindow => {
+            if (
+              this.extension.hasPermission("menus") ||
+              this.extension.hasPermission("contextMenus")
+            ) {
+              browserWindow.document.addEventListener("popupshowing", this);
+            }
+          },
+          onPlacedInPanel: buttonNode => onPlacedHandler(buttonNode, true),
+          onPlacedInUrlbar: buttonNode => onPlacedHandler(buttonNode, false),
+          onRemovedFromWindow: browserWindow => {
+            browserWindow.document.removeEventListener("popupshowing", this);
+          },
+        })
+      );
+
+      if (this.extension.startupReason != "APP_STARTUP") {
+        // Make sure the browser telemetry has the correct state for this widget.
+        // Defer loading BrowserUsageTelemetry until after startup is complete.
+        ExtensionParent.browserStartupPromise.then(() => {
+          BrowserUsageTelemetry.recordWidgetChange(
+            widgetId,
+            this.browserPageAction.pinnedToUrlbar
+              ? "page-action-buttons"
+              : null,
+            "addon"
+          );
+        });
+      }
+
+      // If the page action is only enabled in some URLs, do pattern matching in
+      // the active tabs and update the button if necessary.
+      if (this.action.getProperty(null, "enabled") === undefined) {
+        for (let window of windowTracker.browserWindows()) {
+          let tab = window.gBrowser.selectedTab;
+          if (this.action.isShownForTab(tab)) {
+            this.updateButton(window);
+          }
+        }
+      }
+    }
+  }
+
+  onShutdown(isAppShutdown) {
+    pageActionMap.delete(this.extension);
+    this.action.onShutdown();
+
+    // Removing the browser page action causes PageActions to forget about it
+    // across app restarts, so don't remove it on app shutdown, but do remove
+    // it on all other shutdowns since there's no guarantee the action will be
+    // coming back.
+    if (!isAppShutdown && this.browserPageAction) {
+      this.browserPageAction.remove();
+      this.browserPageAction = null;
+    }
+  }
+
+  // Updates the page action button in the given window to reflect the
+  // properties of the currently selected tab:
+  //
+  // Updates "tooltiptext" and "aria-label" to match "title" property.
+  // Updates "image" to match the "icon" property.
+  // Enables or disables the icon, based on the "enabled" and "patternMatching" properties.
+  updateButton(window) {
+    let tab = window.gBrowser.selectedTab;
+    let tabData = this.action.getContextData(tab);
+    let last = this.lastValues.get(window);
+
+    window.requestAnimationFrame(() => {
+      // If we get called just before shutdown, we might have been destroyed by
+      // this point.
+      if (!this.browserPageAction) {
+        return;
+      }
+
+      let title = tabData.title || this.extension.name;
+      if (last.title !== title) {
+        this.browserPageAction.setTitle(title, window);
+        last.title = title;
+      }
+
+      let enabled =
+        tabData.enabled != null ? tabData.enabled : tabData.patternMatching;
+      if (last.enabled !== enabled) {
+        this.browserPageAction.setDisabled(!enabled, window);
+        last.enabled = enabled;
+      }
+
+      let icon = tabData.icon;
+      if (last.icon !== icon) {
+        this.browserPageAction.setIconURL(icon, window);
+        last.icon = icon;
+      }
+    });
+  }
+
+  /**
+   * Triggers this page action for the given window, with the same effects as
+   * if it were clicked by a user.
+   *
+   * This has no effect if the page action is hidden for the selected tab.
+   *
+   * @param {Window} window
+   */
+  triggerAction(window) {
+    this.handleClick(window, { button: 0, modifiers: [] });
+  }
+
+  handleEvent(event) {
+    switch (event.type) {
+      case "popupshowing":
+        const menu = event.target;
+        const trigger = menu.triggerNode;
+        const getActionId = () => {
+          let actionId = trigger.getAttribute("actionid");
+          if (actionId) {
+            return actionId;
+          }
+          // When a page action is clicked, triggerNode will be an ancestor of
+          // a node corresponding to an action. triggerNode will be the page
+          // action node itself when a page action is selected with the
+          // keyboard. That's because the semantic meaning of page action is on
+          // an hbox that contains an <image>.
+          for (let n = trigger; n && !actionId; n = n.parentElement) {
+            if (n.id == "page-action-buttons" || n.localName == "panelview") {
+              // We reached the page-action-buttons or panelview container.
+              // Stop looking; no action was found.
+              break;
+            }
+            actionId = n.getAttribute("actionid");
+          }
+          return actionId;
+        };
+        if (
+          menu.id === "pageActionContextMenu" &&
+          trigger &&
+          getActionId() === this.browserPageAction.id &&
+          !this.browserPageAction.getDisabled(trigger.ownerGlobal)
+        ) {
+          global.actionContextMenu({
+            extension: this.extension,
+            onPageAction: true,
+            menu: menu,
+          });
+        }
+        break;
+    }
+  }
+
+  // Handles a click event on the page action button for the given
+  // window.
+  // If the page action has a |popup| property, a panel is opened to
+  // that URL. Otherwise, a "click" event is emitted, and dispatched to
+  // the any click listeners in the add-on.
+  async handleClick(window, clickInfo) {
+    const { extension } = this;
+
+    ExtensionTelemetry.pageActionPopupOpen.stopwatchStart(extension, this);
+    let tab = window.gBrowser.selectedTab;
+    let popupURL = this.action.triggerClickOrPopup(tab, clickInfo);
+
+    // If the widget has a popup URL defined, we open a popup, but do not
+    // dispatch a click event to the extension.
+    // If it has no popup URL defined, we dispatch a click event, but do not
+    // open a popup.
+    if (popupURL) {
+      if (this.popupNode && this.popupNode.panel.state !== "closed") {
+        // The panel is being toggled closed.
+        ExtensionTelemetry.pageActionPopupOpen.stopwatchCancel(extension, this);
+        window.BrowserPageActions.togglePanelForAction(
+          this.browserPageAction,
+          this.popupNode.panel
+        );
+        return;
+      }
+
+      this.popupNode = new PanelPopup(
+        extension,
+        window.document,
+        popupURL,
+        this.browserStyle
+      );
+      // Remove popupNode when it is closed.
+      this.popupNode.panel.addEventListener(
+        "popuphiding",
+        () => {
+          this.popupNode = undefined;
+        },
+        { once: true }
+      );
+      await this.popupNode.contentReady;
+      window.BrowserPageActions.togglePanelForAction(
+        this.browserPageAction,
+        this.popupNode.panel
+      );
+      ExtensionTelemetry.pageActionPopupOpen.stopwatchFinish(extension, this);
+    } else {
+      ExtensionTelemetry.pageActionPopupOpen.stopwatchCancel(extension, this);
+    }
+  }
+
+  PERSISTENT_EVENTS = {
+    onClicked({ context, fire }) {
+      const { extension } = this;
+      const { tabManager } = extension;
+
+      let listener = async (_event, tab, clickInfo) => {
+        if (fire.wakeup) {
+          await fire.wakeup();
+        }
+        // TODO: we should double-check if the tab is already being closed by the time
+        // the background script got started and we converted the primed listener.
+        context?.withPendingBrowser(tab.linkedBrowser, () =>
+          fire.sync(tabManager.convert(tab), clickInfo)
+        );
+      };
+
+      this.on("click", listener);
+      return {
+        unregister: () => {
+          this.off("click", listener);
+        },
+        convert(newFire, extContext) {
+          fire = newFire;
+          context = extContext;
+        },
+      };
+    },
+  };
+
+  getAPI(context) {
+    const { action } = this;
+
+    return {
+      pageAction: {
+        ...action.api(context),
+
+        onClicked: new EventManager({
+          context,
+          module: "pageAction",
+          event: "onClicked",
+          inputHandling: true,
+          extensionApi: this,
+        }).api(),
+
+        openPopup: () => {
+          let window = windowTracker.topWindow;
+          this.triggerAction(window);
+        },
+      },
+    };
+  }
+};
+
+global.pageActionFor = this.pageAction.for;
diff --git a/browser/components/extensions/parent/ext-pkcs11.js b/browser/components/extensions/parent/ext-pkcs11.js
new file mode 100644
index 0000000000..696133bfc5
--- /dev/null
+++ b/browser/components/extensions/parent/ext-pkcs11.js
@@ -0,0 +1,187 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  NativeManifests: "resource://gre/modules/NativeManifests.sys.mjs",
+  ctypes: "resource://gre/modules/ctypes.sys.mjs",
+});
+
+XPCOMUtils.defineLazyServiceGetter(
+  this,
+  "pkcs11db",
+  "@mozilla.org/security/pkcs11moduledb;1",
+  "nsIPKCS11ModuleDB"
+);
+
+// eslint-disable-next-line mozilla/reject-importGlobalProperties
+Cu.importGlobalProperties(["PathUtils"]);
+
+var { DefaultMap } = ExtensionUtils;
+
+const findModuleByPath = function (path) {
+  for (let module of pkcs11db.listModules()) {
+    if (module && module.libName === path) {
+      return module;
+    }
+  }
+  return null;
+};
+
+this.pkcs11 = class extends ExtensionAPI {
+  getAPI(context) {
+    let manifestCache = new DefaultMap(async name => {
+      let hostInfo = await NativeManifests.lookupManifest(
+        "pkcs11",
+        name,
+        context
+      );
+      if (hostInfo) {
+        // We don't normalize the absolute path below because
+        // `Path.normalize` throws when the target file doesn't
+        // exist, and that might be the case on non Windows
+        // builds.
+        let absolutePath = PathUtils.isAbsolute(hostInfo.manifest.path)
+          ? hostInfo.manifest.path
+          : PathUtils.joinRelative(
+              PathUtils.parent(hostInfo.path),
+              hostInfo.manifest.path
+            );
+
+        if (AppConstants.platform === "win") {
+          // On Windows, `hostInfo.manifest.path` is expected to be a normalized
+          // absolute path. On other platforms, this path may be relative but we
+          // cannot use `PathUtils.normalize()` on non-absolute paths.
+          absolutePath = PathUtils.normalize(absolutePath);
+          hostInfo.manifest.path = absolutePath;
+        }
+
+        // PathUtils.filename throws if the path is not an absolute path.
+        // The result is expected to be the basename of the file (without
+        // the dir path and the extension) so it is fine to use an absolute
+        // path that may not be normalized (non-Windows platforms).
+        let manifestLib = PathUtils.filename(absolutePath);
+
+        if (AppConstants.platform !== "linux") {
+          manifestLib = manifestLib.toLowerCase(manifestLib);
+        }
+        if (
+          manifestLib !== ctypes.libraryName("nssckbi") &&
+          manifestLib !== ctypes.libraryName("osclientcerts") &&
+          manifestLib !== ctypes.libraryName("ipcclientcerts")
+        ) {
+          return hostInfo.manifest;
+        }
+      }
+      return Promise.reject({ message: `No such PKCS#11 module ${name}` });
+    });
+    return {
+      pkcs11: {
+        /**
+         * Verify whether a given PKCS#11 module is installed.
+         *
+         * @param {string} name The name of the module, as specified in
+         *                      the manifest file.
+         * @returns {Promise} A Promise that resolves to true if the package
+         *                    is installed, or false if it is not. May be
+         *                    rejected if the module could not be found.
+         */
+        async isModuleInstalled(name) {
+          let manifest = await manifestCache.get(name);
+          return findModuleByPath(manifest.path) !== null;
+        },
+        /**
+         * Install a PKCS#11 module
+         *
+         * @param {string} name The name of the module, as specified in
+         *                      the manifest file.
+         * @param {integer} [flags = 0] Any flags to be passed on to the
+         *                              nsIPKCS11ModuleDB.addModule method
+         * @returns {Promise} When the Promise resolves, the module will have
+         *                    been installed. When it is rejected, the module
+         *                    either is already installed or could not be
+         *                    installed for some reason.
+         */
+        async installModule(name, flags = 0) {
+          let manifest = await manifestCache.get(name);
+          if (!manifest.description) {
+            return Promise.reject({
+              message: `The description field in the manifest for PKCS#11 module ${name} must have a value`,
+            });
+          }
+          pkcs11db.addModule(manifest.description, manifest.path, flags, 0);
+        },
+        /**
+         * Uninstall a PKCS#11 module
+         *
+         * @param {string} name The name of the module, as specified in
+         *                      the manifest file.
+         * @returns {Promise}. When the Promise resolves, the module will have
+         *                     been uninstalled. When it is rejected, the
+         *                     module either was not installed or could not be
+         *                     uninstalled for some reason.
+         */
+        async uninstallModule(name) {
+          let manifest = await manifestCache.get(name);
+          let module = findModuleByPath(manifest.path);
+          if (!module) {
+            return Promise.reject({
+              message: `The PKCS#11 module ${name} is not loaded`,
+            });
+          }
+          pkcs11db.deleteModule(module.name);
+        },
+        /**
+         * Get a list of slots for a given PKCS#11 module, with
+         * information on the token (if any) in the slot.
+         *
+         * The PKCS#11 standard defines slots as an abstract concept
+         * that may or may not have at most one token. In practice, when
+         * using PKCS#11 for smartcards (the most likely use case of
+         * PKCS#11 for Firefox), a slot corresponds to a cardreader, and
+         * a token corresponds to a card.
+         *
+         * @param {string} name The name of the PKCS#11 module, as
+         *                 specified in the manifest file.
+         * @returns {Promise} A promise that resolves to an array of objects
+         *                    with two properties.  The `name` object contains
+         *                    the name of the slot; the `token` object is null
+         *                    if there is no token in the slot, or is an object
+         *                    describing various properties of the token if
+         *                    there is.
+         */
+        async getModuleSlots(name) {
+          let manifest = await manifestCache.get(name);
+          let module = findModuleByPath(manifest.path);
+          if (!module) {
+            return Promise.reject({
+              message: `The module ${name} is not installed`,
+            });
+          }
+          let rv = [];
+          for (let slot of module.listSlots()) {
+            let token = slot.getToken();
+            let slotobj = {
+              name: slot.name,
+              token: null,
+            };
+            if (slot.status != 1 /* SLOT_NOT_PRESENT */) {
+              slotobj.token = {
+                name: token.tokenName,
+                manufacturer: token.tokenManID,
+                HWVersion: token.tokenHWVersion,
+                FWVersion: token.tokenFWVersion,
+                serial: token.tokenSerialNumber,
+                isLoggedIn: token.isLoggedIn(),
+              };
+            }
+            rv.push(slotobj);
+          }
+          return rv;
+        },
+      },
+    };
+  }
+};
diff --git a/browser/components/extensions/parent/ext-search.js b/browser/components/extensions/parent/ext-search.js
new file mode 100644
index 0000000000..be51f5a17a
--- /dev/null
+++ b/browser/components/extensions/parent/ext-search.js
@@ -0,0 +1,118 @@
+/* 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/. */
+
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+
+"use strict";
+
+var { ExtensionError } = ExtensionUtils;
+
+const dispositionMap = {
+  CURRENT_TAB: "current",
+  NEW_TAB: "tab",
+  NEW_WINDOW: "window",
+};
+
+this.search = class extends ExtensionAPI {
+  getAPI(context) {
+    function getTarget({ tabId, disposition, defaultDisposition }) {
+      let tab, where;
+      if (disposition) {
+        if (tabId) {
+          throw new ExtensionError(`Cannot set both 'disposition' and 'tabId'`);
+        }
+        where = dispositionMap[disposition];
+      } else if (tabId) {
+        tab = tabTracker.getTab(tabId);
+      } else {
+        where = dispositionMap[defaultDisposition];
+      }
+      return { tab, where };
+    }
+
+    return {
+      search: {
+        async get() {
+          await searchInitialized;
+          let visibleEngines = await Services.search.getVisibleEngines();
+          let defaultEngine = await Services.search.getDefault();
+          return Promise.all(
+            visibleEngines.map(async engine => {
+              let favIconUrl;
+              if (engine.iconURI) {
+                // Convert moz-extension:-URLs to data:-URLs to make sure that
+                // extensions can see icons from other extensions, even if they
+                // are not web-accessible.
+                // Also prevents leakage of extension UUIDs to other extensions..
+                if (
+                  engine.iconURI.schemeIs("moz-extension") &&
+                  engine.iconURI.host !== context.extension.uuid
+                ) {
+                  favIconUrl = await ExtensionUtils.makeDataURI(
+                    engine.iconURI.spec
+                  );
+                } else {
+                  favIconUrl = engine.iconURI.spec;
+                }
+              }
+
+              return {
+                name: engine.name,
+                isDefault: engine.name === defaultEngine.name,
+                alias: engine.alias || undefined,
+                favIconUrl,
+              };
+            })
+          );
+        },
+
+        async search(searchProperties) {
+          await searchInitialized;
+          let engine;
+
+          if (searchProperties.engine) {
+            engine = Services.search.getEngineByName(searchProperties.engine);
+            if (!engine) {
+              throw new ExtensionError(
+                `${searchProperties.engine} was not found`
+              );
+            }
+          }
+
+          let { tab, where } = getTarget({
+            tabId: searchProperties.tabId,
+            disposition: searchProperties.disposition,
+            defaultDisposition: "NEW_TAB",
+          });
+
+          await windowTracker.topWindow.BrowserSearch.loadSearchFromExtension({
+            query: searchProperties.query,
+            where,
+            engine,
+            tab,
+            triggeringPrincipal: context.principal,
+          });
+        },
+
+        async query(queryProperties) {
+          await searchInitialized;
+
+          let { tab, where } = getTarget({
+            tabId: queryProperties.tabId,
+            disposition: queryProperties.disposition,
+            defaultDisposition: "CURRENT_TAB",
+          });
+
+          await windowTracker.topWindow.BrowserSearch.loadSearchFromExtension({
+            query: queryProperties.text,
+            where,
+            tab,
+            triggeringPrincipal: context.principal,
+          });
+        },
+      },
+    };
+  }
+};
diff --git a/browser/components/extensions/parent/ext-sessions.js b/browser/components/extensions/parent/ext-sessions.js
new file mode 100644
index 0000000000..eb50a147f0
--- /dev/null
+++ b/browser/components/extensions/parent/ext-sessions.js
@@ -0,0 +1,274 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var { ExtensionError, promiseObserved } = ExtensionUtils;
+
+ChromeUtils.defineESModuleGetters(this, {
+  AddonManagerPrivate: "resource://gre/modules/AddonManager.sys.mjs",
+  SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs",
+});
+
+const SS_ON_CLOSED_OBJECTS_CHANGED = "sessionstore-closed-objects-changed";
+
+const getRecentlyClosed = (maxResults, extension) => {
+  let recentlyClosed = [];
+
+  // Get closed windows
+  // Closed private windows are not stored in sessionstore, we do
+  // not need to check access for that.
+  let closedWindowData = SessionStore.getClosedWindowData();
+  for (let window of closedWindowData) {
+    recentlyClosed.push({
+      lastModified: window.closedAt,
+      window: Window.convertFromSessionStoreClosedData(extension, window),
+    });
+  }
+
+  // Get closed tabs
+  // Private closed tabs are in sessionstore if the owning window is still open .
+  for (let window of windowTracker.browserWindows()) {
+    if (!extension.canAccessWindow(window)) {
+      continue;
+    }
+    let closedTabData = SessionStore.getClosedTabDataForWindow(window);
+    for (let tab of closedTabData) {
+      recentlyClosed.push({
+        lastModified: tab.closedAt,
+        tab: Tab.convertFromSessionStoreClosedData(extension, tab, window),
+      });
+    }
+  }
+
+  // Sort windows and tabs
+  recentlyClosed.sort((a, b) => b.lastModified - a.lastModified);
+  return recentlyClosed.slice(0, maxResults);
+};
+
+const createSession = async function createSession(
+  restored,
+  extension,
+  sessionId
+) {
+  if (!restored) {
+    throw new ExtensionError(
+      `Could not restore object using sessionId ${sessionId}.`
+    );
+  }
+  let sessionObj = { lastModified: Date.now() };
+  if (restored instanceof Ci.nsIDOMChromeWindow) {
+    await promiseObserved(
+      "sessionstore-single-window-restored",
+      subject => subject == restored
+    );
+    sessionObj.window = extension.windowManager.convert(restored, {
+      populate: true,
+    });
+    return sessionObj;
+  }
+  sessionObj.tab = extension.tabManager.convert(restored);
+  return sessionObj;
+};
+
+const getEncodedKey = function getEncodedKey(extensionId, key) {
+  // Throw if using a temporary extension id.
+  if (AddonManagerPrivate.isTemporaryInstallID(extensionId)) {
+    let message =
+      "Sessions API storage methods will not work with a temporary addon ID. " +
+      "Please add an explicit addon ID to your manifest.";
+    throw new ExtensionError(message);
+  }
+
+  return `extension:${extensionId}:${key}`;
+};
+
+this.sessions = class extends ExtensionAPIPersistent {
+  PERSISTENT_EVENTS = {
+    onChanged({ fire }) {
+      let observer = () => {
+        fire.async();
+      };
+
+      Services.obs.addObserver(observer, SS_ON_CLOSED_OBJECTS_CHANGED);
+      return {
+        unregister() {
+          Services.obs.removeObserver(observer, SS_ON_CLOSED_OBJECTS_CHANGED);
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+  };
+
+  getAPI(context) {
+    let { extension } = context;
+
+    function getTabParams(key, id) {
+      let encodedKey = getEncodedKey(extension.id, key);
+      let tab = tabTracker.getTab(id);
+      if (!context.canAccessWindow(tab.ownerGlobal)) {
+        throw new ExtensionError(`Invalid tab ID: ${id}`);
+      }
+      return { encodedKey, tab };
+    }
+
+    function getWindowParams(key, id) {
+      let encodedKey = getEncodedKey(extension.id, key);
+      let win = windowTracker.getWindow(id, context);
+      return { encodedKey, win };
+    }
+
+    return {
+      sessions: {
+        async getRecentlyClosed(filter) {
+          await SessionStore.promiseInitialized;
+          let maxResults =
+            filter.maxResults == undefined
+              ? this.MAX_SESSION_RESULTS
+              : filter.maxResults;
+          return getRecentlyClosed(maxResults, extension);
+        },
+
+        async forgetClosedTab(windowId, sessionId) {
+          await SessionStore.promiseInitialized;
+          let window = windowTracker.getWindow(windowId, context);
+          let closedTabData = SessionStore.getClosedTabDataForWindow(window);
+
+          let closedTabIndex = closedTabData.findIndex(closedTab => {
+            return closedTab.closedId === parseInt(sessionId, 10);
+          });
+
+          if (closedTabIndex < 0) {
+            throw new ExtensionError(
+              `Could not find closed tab using sessionId ${sessionId}.`
+            );
+          }
+
+          SessionStore.forgetClosedTab(window, closedTabIndex);
+        },
+
+        async forgetClosedWindow(sessionId) {
+          await SessionStore.promiseInitialized;
+          let closedWindowData = SessionStore.getClosedWindowData();
+
+          let closedWindowIndex = closedWindowData.findIndex(closedWindow => {
+            return closedWindow.closedId === parseInt(sessionId, 10);
+          });
+
+          if (closedWindowIndex < 0) {
+            throw new ExtensionError(
+              `Could not find closed window using sessionId ${sessionId}.`
+            );
+          }
+
+          SessionStore.forgetClosedWindow(closedWindowIndex);
+        },
+
+        async restore(sessionId) {
+          await SessionStore.promiseInitialized;
+          let session, closedId;
+          if (sessionId) {
+            closedId = sessionId;
+            session = SessionStore.undoCloseById(
+              closedId,
+              extension.privateBrowsingAllowed
+            );
+          } else if (SessionStore.lastClosedObjectType == "window") {
+            // If the most recently closed object is a window, just undo closing the most recent window.
+            session = SessionStore.undoCloseWindow(0);
+          } else {
+            // It is a tab, and we cannot call SessionStore.undoCloseTab without a window,
+            // so we must find the tab in which case we can just use its closedId.
+            let recentlyClosedTabs = [];
+            for (let window of windowTracker.browserWindows()) {
+              let closedTabData =
+                SessionStore.getClosedTabDataForWindow(window);
+              for (let tab of closedTabData) {
+                recentlyClosedTabs.push(tab);
+              }
+            }
+
+            if (recentlyClosedTabs.length) {
+              // Sort the tabs.
+              recentlyClosedTabs.sort((a, b) => b.closedAt - a.closedAt);
+
+              // Use the closedId of the most recently closed tab to restore it.
+              closedId = recentlyClosedTabs[0].closedId;
+              session = SessionStore.undoCloseById(
+                closedId,
+                extension.privateBrowsingAllowed
+              );
+            }
+          }
+          return createSession(session, extension, closedId);
+        },
+
+        setTabValue(tabId, key, value) {
+          let { tab, encodedKey } = getTabParams(key, tabId);
+
+          SessionStore.setCustomTabValue(
+            tab,
+            encodedKey,
+            JSON.stringify(value)
+          );
+        },
+
+        async getTabValue(tabId, key) {
+          let { tab, encodedKey } = getTabParams(key, tabId);
+
+          let value = SessionStore.getCustomTabValue(tab, encodedKey);
+          if (value) {
+            return JSON.parse(value);
+          }
+
+          return undefined;
+        },
+
+        removeTabValue(tabId, key) {
+          let { tab, encodedKey } = getTabParams(key, tabId);
+
+          SessionStore.deleteCustomTabValue(tab, encodedKey);
+        },
+
+        setWindowValue(windowId, key, value) {
+          let { win, encodedKey } = getWindowParams(key, windowId);
+
+          SessionStore.setCustomWindowValue(
+            win,
+            encodedKey,
+            JSON.stringify(value)
+          );
+        },
+
+        async getWindowValue(windowId, key) {
+          let { win, encodedKey } = getWindowParams(key, windowId);
+
+          let value = SessionStore.getCustomWindowValue(win, encodedKey);
+          if (value) {
+            return JSON.parse(value);
+          }
+
+          return undefined;
+        },
+
+        removeWindowValue(windowId, key) {
+          let { win, encodedKey } = getWindowParams(key, windowId);
+
+          SessionStore.deleteCustomWindowValue(win, encodedKey);
+        },
+
+        onChanged: new EventManager({
+          context,
+          module: "sessions",
+          event: "onChanged",
+          extensionApi: this,
+        }).api(),
+      },
+    };
+  }
+};
diff --git a/browser/components/extensions/parent/ext-sidebarAction.js b/browser/components/extensions/parent/ext-sidebarAction.js
new file mode 100644
index 0000000000..a07f9a9f0e
--- /dev/null
+++ b/browser/components/extensions/parent/ext-sidebarAction.js
@@ -0,0 +1,532 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var { ExtensionParent } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionParent.sys.mjs"
+);
+
+var { ExtensionError } = ExtensionUtils;
+
+var { IconDetails } = ExtensionParent;
+
+// WeakMap[Extension -> SidebarAction]
+let sidebarActionMap = new WeakMap();
+
+const sidebarURL = "chrome://browser/content/webext-panels.xhtml";
+
+/**
+ * Responsible for the sidebar_action section of the manifest as well
+ * as the associated sidebar browser.
+ */
+this.sidebarAction = class extends ExtensionAPI {
+  static for(extension) {
+    return sidebarActionMap.get(extension);
+  }
+
+  onManifestEntry(entryName) {
+    let { extension } = this;
+
+    extension.once("ready", this.onReady.bind(this));
+
+    let options = extension.manifest.sidebar_action;
+
+    // Add the extension to the sidebar menu.  The sidebar widget will copy
+    // from that when it is viewed, so we shouldn't need to update that.
+    let widgetId = makeWidgetId(extension.id);
+    this.id = `${widgetId}-sidebar-action`;
+    this.menuId = `menu_${this.id}`;
+    this.buttonId = `button_${this.id}`;
+
+    this.browserStyle = options.browser_style;
+
+    this.defaults = {
+      enabled: true,
+      title: options.default_title || extension.name,
+      icon: IconDetails.normalize({ path: options.default_icon }, extension),
+      panel: options.default_panel || "",
+    };
+    this.globals = Object.create(this.defaults);
+
+    this.tabContext = new TabContext(target => {
+      let window = target.ownerGlobal;
+      if (target === window) {
+        return this.globals;
+      }
+      return this.tabContext.get(window);
+    });
+
+    // We need to ensure our elements are available before session restore.
+    this.windowOpenListener = window => {
+      this.createMenuItem(window, this.globals);
+    };
+    windowTracker.addOpenListener(this.windowOpenListener);
+
+    this.updateHeader = event => {
+      let window = event.target.ownerGlobal;
+      let details = this.tabContext.get(window.gBrowser.selectedTab);
+      let header = window.document.getElementById("sidebar-switcher-target");
+      if (window.SidebarUI.currentID === this.id) {
+        this.setMenuIcon(header, details);
+      }
+    };
+
+    this.windowCloseListener = window => {
+      let header = window.document.getElementById("sidebar-switcher-target");
+      if (header) {
+        header.removeEventListener("SidebarShown", this.updateHeader);
+      }
+    };
+    windowTracker.addCloseListener(this.windowCloseListener);
+
+    sidebarActionMap.set(extension, this);
+  }
+
+  onReady() {
+    this.build();
+  }
+
+  onShutdown(isAppShutdown) {
+    sidebarActionMap.delete(this.this);
+
+    this.tabContext.shutdown();
+
+    // Don't remove everything on app shutdown so session restore can handle
+    // restoring open sidebars.
+    if (isAppShutdown) {
+      return;
+    }
+
+    for (let window of windowTracker.browserWindows()) {
+      let { document, SidebarUI } = window;
+      if (SidebarUI.currentID === this.id) {
+        SidebarUI.hide();
+      }
+      let menu = document.getElementById(this.menuId);
+      if (menu) {
+        menu.remove();
+      }
+      let button = document.getElementById(this.buttonId);
+      if (button) {
+        button.remove();
+      }
+      let header = document.getElementById("sidebar-switcher-target");
+      header.removeEventListener("SidebarShown", this.updateHeader);
+      SidebarUI.sidebars.delete(this.id);
+    }
+    windowTracker.removeOpenListener(this.windowOpenListener);
+    windowTracker.removeCloseListener(this.windowCloseListener);
+  }
+
+  static onUninstall(id) {
+    const sidebarId = `${makeWidgetId(id)}-sidebar-action`;
+    for (let window of windowTracker.browserWindows()) {
+      let { SidebarUI } = window;
+      if (SidebarUI.lastOpenedId === sidebarId) {
+        SidebarUI.lastOpenedId = null;
+      }
+    }
+  }
+
+  build() {
+    // eslint-disable-next-line mozilla/balanced-listeners
+    this.tabContext.on("tab-select", (evt, tab) => {
+      this.updateWindow(tab.ownerGlobal);
+    });
+
+    let install = this.extension.startupReason === "ADDON_INSTALL";
+    for (let window of windowTracker.browserWindows()) {
+      this.updateWindow(window);
+      let { SidebarUI } = window;
+      if (
+        (install && this.extension.manifest.sidebar_action.open_at_install) ||
+        SidebarUI.lastOpenedId == this.id
+      ) {
+        SidebarUI.show(this.id);
+      }
+    }
+  }
+
+  createMenuItem(window, details) {
+    if (!this.extension.canAccessWindow(window)) {
+      return;
+    }
+    let { document, SidebarUI } = window;
+    let keyId = `ext-key-id-${this.id}`;
+
+    SidebarUI.sidebars.set(this.id, {
+      title: details.title,
+      url: sidebarURL,
+      menuId: this.menuId,
+      buttonId: this.buttonId,
+      // The following properties are specific to extensions
+      extensionId: this.extension.id,
+      panel: details.panel,
+      browserStyle: this.browserStyle,
+    });
+
+    let header = document.getElementById("sidebar-switcher-target");
+    header.addEventListener("SidebarShown", this.updateHeader);
+
+    // Insert a menuitem for View->Show Sidebars.
+    let menuitem = document.createXULElement("menuitem");
+    menuitem.setAttribute("id", this.menuId);
+    menuitem.setAttribute("type", "checkbox");
+    menuitem.setAttribute("label", details.title);
+    menuitem.setAttribute("oncommand", `SidebarUI.toggle("${this.id}");`);
+    menuitem.setAttribute("class", "menuitem-iconic webextension-menuitem");
+    menuitem.setAttribute("key", keyId);
+    this.setMenuIcon(menuitem, details);
+
+    // Insert a toolbarbutton for the sidebar dropdown selector.
+    let toolbarbutton = document.createXULElement("toolbarbutton");
+    toolbarbutton.setAttribute("id", this.buttonId);
+    toolbarbutton.setAttribute("label", details.title);
+    toolbarbutton.setAttribute("oncommand", `SidebarUI.show("${this.id}");`);
+    toolbarbutton.setAttribute(
+      "class",
+      "subviewbutton subviewbutton-iconic webextension-menuitem"
+    );
+    toolbarbutton.setAttribute("key", keyId);
+    this.setMenuIcon(toolbarbutton, details);
+
+    document.getElementById("viewSidebarMenu").appendChild(menuitem);
+    let separator = document.getElementById("sidebar-extensions-separator");
+    separator.parentNode.insertBefore(toolbarbutton, separator);
+    SidebarUI.updateShortcut({ button: toolbarbutton });
+
+    return menuitem;
+  }
+
+  setMenuIcon(menuitem, details) {
+    let getIcon = size =>
+      IconDetails.escapeUrl(
+        IconDetails.getPreferredIcon(details.icon, this.extension, size).icon
+      );
+
+    menuitem.setAttribute(
+      "style",
+      `
+      --webextension-menuitem-image: url("${getIcon(16)}");
+      --webextension-menuitem-image-2x: url("${getIcon(32)}");
+    `
+    );
+  }
+
+  /**
+   * Update the menu items with the tab context data in `tabData`.
+   *
+   * @param {ChromeWindow} window
+   *        Browser chrome window.
+   * @param {object} tabData
+   *        Tab specific sidebar configuration.
+   */
+  updateButton(window, tabData) {
+    let { document, SidebarUI } = window;
+    let title = tabData.title || this.extension.name;
+    let menu = document.getElementById(this.menuId);
+    if (!menu) {
+      menu = this.createMenuItem(window, tabData);
+    }
+
+    let urlChanged = tabData.panel !== SidebarUI.sidebars.get(this.id).panel;
+    if (urlChanged) {
+      SidebarUI.sidebars.get(this.id).panel = tabData.panel;
+    }
+
+    menu.setAttribute("label", title);
+    this.setMenuIcon(menu, tabData);
+
+    let button = document.getElementById(this.buttonId);
+    button.setAttribute("label", title);
+    this.setMenuIcon(button, tabData);
+
+    // Update the sidebar if this extension is the current sidebar.
+    if (SidebarUI.currentID === this.id) {
+      SidebarUI.title = title;
+      let header = document.getElementById("sidebar-switcher-target");
+      this.setMenuIcon(header, tabData);
+      if (SidebarUI.isOpen && urlChanged) {
+        SidebarUI.show(this.id);
+      }
+    }
+  }
+
+  /**
+   * Update the menu items for a given window.
+   *
+   * @param {ChromeWindow} window
+   *        Browser chrome window.
+   */
+  updateWindow(window) {
+    if (!this.extension.canAccessWindow(window)) {
+      return;
+    }
+    let nativeTab = window.gBrowser.selectedTab;
+    this.updateButton(window, this.tabContext.get(nativeTab));
+  }
+
+  /**
+   * Update the menu items when the extension changes the icon,
+   * title, url, etc. If it only changes a parameter for a single tab, `target`
+   * will be that tab. If it only changes a parameter for a single window,
+   * `target` will be that window. Otherwise `target` will be null.
+   *
+   * @param {XULElement|ChromeWindow|null} target
+   *        Browser tab or browser chrome window, may be null.
+   */
+  updateOnChange(target) {
+    if (target) {
+      let window = target.ownerGlobal;
+      if (target === window || target.selected) {
+        this.updateWindow(window);
+      }
+    } else {
+      for (let window of windowTracker.browserWindows()) {
+        this.updateWindow(window);
+      }
+    }
+  }
+
+  /**
+   * Gets the target object corresponding to the `details` parameter of the various
+   * get* and set* API methods.
+   *
+   * @param {object} details
+   *        An object with optional `tabId` or `windowId` properties.
+   * @param {number} [details.tabId]
+   *        The target tab.
+   * @param {number} [details.windowId]
+   *        The target window.
+   * @throws if both `tabId` and `windowId` are specified, or if they are invalid.
+   * @returns {XULElement|ChromeWindow|null}
+   *        If a `tabId` was specified, the corresponding XULElement tab.
+   *        If a `windowId` was specified, the corresponding ChromeWindow.
+   *        Otherwise, `null`.
+   */
+  getTargetFromDetails({ tabId, windowId }) {
+    if (tabId != null && windowId != null) {
+      throw new ExtensionError(
+        "Only one of tabId and windowId can be specified."
+      );
+    }
+    let target = null;
+    if (tabId != null) {
+      target = tabTracker.getTab(tabId);
+      if (!this.extension.canAccessWindow(target.ownerGlobal)) {
+        throw new ExtensionError(`Invalid tab ID: ${tabId}`);
+      }
+    } else if (windowId != null) {
+      target = windowTracker.getWindow(windowId);
+      if (!this.extension.canAccessWindow(target)) {
+        throw new ExtensionError(`Invalid window ID: ${windowId}`);
+      }
+    }
+    return target;
+  }
+
+  /**
+   * Gets the data associated with a tab, window, or the global one.
+   *
+   * @param {XULElement|ChromeWindow|null} target
+   *        A XULElement tab, a ChromeWindow, or null for the global data.
+   * @returns {object}
+   *        The icon, title, panel, etc. associated with the target.
+   */
+  getContextData(target) {
+    if (target) {
+      return this.tabContext.get(target);
+    }
+    return this.globals;
+  }
+
+  /**
+   * Set a global, window specific or tab specific property.
+   *
+   * @param {XULElement|ChromeWindow|null} target
+   *        A XULElement tab, a ChromeWindow, or null for the global data.
+   * @param {string} prop
+   *        String property to set ["icon", "title", or "panel"].
+   * @param {string} value
+   *        Value for property.
+   */
+  setProperty(target, prop, value) {
+    let values = this.getContextData(target);
+    if (value === null) {
+      delete values[prop];
+    } else {
+      values[prop] = value;
+    }
+
+    this.updateOnChange(target);
+  }
+
+  /**
+   * Retrieve the value of a global, window specific or tab specific property.
+   *
+   * @param {XULElement|ChromeWindow|null} target
+   *        A XULElement tab, a ChromeWindow, or null for the global data.
+   * @param {string} prop
+   *        String property to retrieve ["icon", "title", or "panel"]
+   * @returns {string} value
+   *          Value of prop.
+   */
+  getProperty(target, prop) {
+    return this.getContextData(target)[prop];
+  }
+
+  setPropertyFromDetails(details, prop, value) {
+    return this.setProperty(this.getTargetFromDetails(details), prop, value);
+  }
+
+  getPropertyFromDetails(details, prop) {
+    return this.getProperty(this.getTargetFromDetails(details), prop);
+  }
+
+  /**
+   * Triggers this sidebar action for the given window, with the same effects as
+   * if it were toggled via menu or toolbarbutton by a user.
+   *
+   * @param {ChromeWindow} window
+   */
+  triggerAction(window) {
+    let { SidebarUI } = window;
+    if (SidebarUI && this.extension.canAccessWindow(window)) {
+      SidebarUI.toggle(this.id);
+    }
+  }
+
+  /**
+   * Opens this sidebar action for the given window.
+   *
+   * @param {ChromeWindow} window
+   */
+  open(window) {
+    let { SidebarUI } = window;
+    if (SidebarUI && this.extension.canAccessWindow(window)) {
+      SidebarUI.show(this.id);
+    }
+  }
+
+  /**
+   * Closes this sidebar action for the given window if this sidebar action is open.
+   *
+   * @param {ChromeWindow} window
+   */
+  close(window) {
+    if (this.isOpen(window)) {
+      window.SidebarUI.hide();
+    }
+  }
+
+  /**
+   * Toogles this sidebar action for the given window
+   *
+   * @param {ChromeWindow} window
+   */
+  toggle(window) {
+    let { SidebarUI } = window;
+    if (!SidebarUI || !this.extension.canAccessWindow(window)) {
+      return;
+    }
+
+    if (!this.isOpen(window)) {
+      SidebarUI.show(this.id);
+    } else {
+      SidebarUI.hide();
+    }
+  }
+
+  /**
+   * Checks whether this sidebar action is open in the given window.
+   *
+   * @param {ChromeWindow} window
+   * @returns {boolean}
+   */
+  isOpen(window) {
+    let { SidebarUI } = window;
+    return SidebarUI.isOpen && this.id == SidebarUI.currentID;
+  }
+
+  getAPI(context) {
+    let { extension } = context;
+    const sidebarAction = this;
+
+    return {
+      sidebarAction: {
+        async setTitle(details) {
+          sidebarAction.setPropertyFromDetails(details, "title", details.title);
+        },
+
+        getTitle(details) {
+          return sidebarAction.getPropertyFromDetails(details, "title");
+        },
+
+        async setIcon(details) {
+          let icon = IconDetails.normalize(details, extension, context);
+          if (!Object.keys(icon).length) {
+            icon = null;
+          }
+          sidebarAction.setPropertyFromDetails(details, "icon", icon);
+        },
+
+        async setPanel(details) {
+          let url;
+          // Clear the url when given null or empty string.
+          if (!details.panel) {
+            url = null;
+          } else {
+            url = context.uri.resolve(details.panel);
+            if (!context.checkLoadURL(url)) {
+              return Promise.reject({
+                message: `Access denied for URL ${url}`,
+              });
+            }
+          }
+
+          sidebarAction.setPropertyFromDetails(details, "panel", url);
+        },
+
+        getPanel(details) {
+          return sidebarAction.getPropertyFromDetails(details, "panel");
+        },
+
+        open() {
+          let window = windowTracker.topWindow;
+          if (context.canAccessWindow(window)) {
+            sidebarAction.open(window);
+          }
+        },
+
+        close() {
+          let window = windowTracker.topWindow;
+          if (context.canAccessWindow(window)) {
+            sidebarAction.close(window);
+          }
+        },
+
+        toggle() {
+          let window = windowTracker.topWindow;
+          if (context.canAccessWindow(window)) {
+            sidebarAction.toggle(window);
+          }
+        },
+
+        isOpen(details) {
+          let { windowId } = details;
+          if (windowId == null) {
+            windowId = Window.WINDOW_ID_CURRENT;
+          }
+          let window = windowTracker.getWindow(windowId, context);
+          return sidebarAction.isOpen(window);
+        },
+      },
+    };
+  }
+};
+
+global.sidebarActionFor = this.sidebarAction.for;
diff --git a/browser/components/extensions/parent/ext-tabs.js b/browser/components/extensions/parent/ext-tabs.js
new file mode 100644
index 0000000000..c8d6b9f6dd
--- /dev/null
+++ b/browser/components/extensions/parent/ext-tabs.js
@@ -0,0 +1,1627 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+ChromeUtils.defineModuleGetter(
+  this,
+  "BrowserUIUtils",
+  "resource:///modules/BrowserUIUtils.jsm"
+);
+ChromeUtils.defineESModuleGetters(this, {
+  DownloadPaths: "resource://gre/modules/DownloadPaths.sys.mjs",
+  ExtensionControlledPopup:
+    "resource:///modules/ExtensionControlledPopup.sys.mjs",
+  PrivateBrowsingUtils: "resource://gre/modules/PrivateBrowsingUtils.sys.mjs",
+  PromiseUtils: "resource://gre/modules/PromiseUtils.sys.mjs",
+  SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs",
+});
+
+XPCOMUtils.defineLazyGetter(this, "strBundle", function () {
+  return Services.strings.createBundle(
+    "chrome://global/locale/extensions.properties"
+  );
+});
+
+var { DefaultMap, ExtensionError } = ExtensionUtils;
+
+const TAB_HIDE_CONFIRMED_TYPE = "tabHideNotification";
+
+const TAB_ID_NONE = -1;
+
+XPCOMUtils.defineLazyGetter(this, "tabHidePopup", () => {
+  return new ExtensionControlledPopup({
+    confirmedType: TAB_HIDE_CONFIRMED_TYPE,
+    anchorId: "alltabs-button",
+    popupnotificationId: "extension-tab-hide-notification",
+    descriptionId: "extension-tab-hide-notification-description",
+    descriptionMessageId: "tabHideControlled.message",
+    getLocalizedDescription: (doc, message, addonDetails) => {
+      let image = doc.createXULElement("image");
+      image.setAttribute("class", "extension-controlled-icon alltabs-icon");
+      return BrowserUIUtils.getLocalizedFragment(
+        doc,
+        message,
+        addonDetails,
+        image
+      );
+    },
+    learnMoreMessageId: "tabHideControlled.learnMore",
+    learnMoreLink: "extension-hiding-tabs",
+  });
+});
+
+function showHiddenTabs(id) {
+  for (let win of Services.wm.getEnumerator("navigator:browser")) {
+    if (win.closed || !win.gBrowser) {
+      continue;
+    }
+
+    for (let tab of win.gBrowser.tabs) {
+      if (
+        tab.hidden &&
+        tab.ownerGlobal &&
+        SessionStore.getCustomTabValue(tab, "hiddenBy") === id
+      ) {
+        win.gBrowser.showTab(tab);
+      }
+    }
+  }
+}
+
+let tabListener = {
+  tabReadyInitialized: false,
+  // Map[tab -> Promise]
+  tabBlockedPromises: new WeakMap(),
+  // Map[tab -> Deferred]
+  tabReadyPromises: new WeakMap(),
+  initializingTabs: new WeakSet(),
+
+  initTabReady() {
+    if (!this.tabReadyInitialized) {
+      windowTracker.addListener("progress", this);
+
+      this.tabReadyInitialized = true;
+    }
+  },
+
+  onLocationChange(browser, webProgress, request, locationURI, flags) {
+    if (webProgress.isTopLevel) {
+      let { gBrowser } = browser.ownerGlobal;
+      let nativeTab = gBrowser.getTabForBrowser(browser);
+
+      // Now we are certain that the first page in the tab was loaded.
+      this.initializingTabs.delete(nativeTab);
+
+      // browser.innerWindowID is now set, resolve the promises if any.
+      let deferred = this.tabReadyPromises.get(nativeTab);
+      if (deferred) {
+        deferred.resolve(nativeTab);
+        this.tabReadyPromises.delete(nativeTab);
+      }
+    }
+  },
+
+  blockTabUntilRestored(nativeTab) {
+    let promise = ExtensionUtils.promiseEvent(nativeTab, "SSTabRestored").then(
+      ({ target }) => {
+        this.tabBlockedPromises.delete(target);
+        return target;
+      }
+    );
+
+    this.tabBlockedPromises.set(nativeTab, promise);
+  },
+
+  /**
+   * Returns a promise that resolves when the tab is ready.
+   * Tabs created via the `tabs.create` method are "ready" once the location
+   * changes to the requested URL. Other tabs are assumed to be ready once their
+   * inner window ID is known.
+   *
+   * @param {XULElement} nativeTab The <tab> element.
+   * @returns {Promise} Resolves with the given tab once ready.
+   */
+  awaitTabReady(nativeTab) {
+    let deferred = this.tabReadyPromises.get(nativeTab);
+    if (!deferred) {
+      let promise = this.tabBlockedPromises.get(nativeTab);
+      if (promise) {
+        return promise;
+      }
+      deferred = PromiseUtils.defer();
+      if (
+        !this.initializingTabs.has(nativeTab) &&
+        (nativeTab.linkedBrowser.innerWindowID ||
+          nativeTab.linkedBrowser.currentURI.spec === "about:blank")
+      ) {
+        deferred.resolve(nativeTab);
+      } else {
+        this.initTabReady();
+        this.tabReadyPromises.set(nativeTab, deferred);
+      }
+    }
+    return deferred.promise;
+  },
+};
+
+const allAttrs = new Set([
+  "attention",
+  "audible",
+  "favIconUrl",
+  "mutedInfo",
+  "sharingState",
+  "title",
+]);
+const allProperties = new Set([
+  "attention",
+  "audible",
+  "discarded",
+  "favIconUrl",
+  "hidden",
+  "isArticle",
+  "mutedInfo",
+  "pinned",
+  "sharingState",
+  "status",
+  "title",
+  "url",
+]);
+const restricted = new Set(["url", "favIconUrl", "title"]);
+
+this.tabs = class extends ExtensionAPIPersistent {
+  static onUpdate(id, manifest) {
+    if (!manifest.permissions || !manifest.permissions.includes("tabHide")) {
+      showHiddenTabs(id);
+    }
+  }
+
+  static onDisable(id) {
+    showHiddenTabs(id);
+    tabHidePopup.clearConfirmation(id);
+  }
+
+  static onUninstall(id) {
+    tabHidePopup.clearConfirmation(id);
+  }
+
+  tabEventRegistrar({ event, listener }) {
+    let { extension } = this;
+    let { tabManager } = extension;
+    return ({ fire }) => {
+      let listener2 = (eventName, eventData, ...args) => {
+        if (!tabManager.canAccessTab(eventData.nativeTab)) {
+          return;
+        }
+
+        listener(fire, eventData, ...args);
+      };
+
+      tabTracker.on(event, listener2);
+      return {
+        unregister() {
+          tabTracker.off(event, listener2);
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    };
+  }
+
+  PERSISTENT_EVENTS = {
+    onActivated: this.tabEventRegistrar({
+      event: "tab-activated",
+      listener: (fire, event) => {
+        let { extension } = this;
+        let { tabId, windowId, previousTabId, previousTabIsPrivate } = event;
+        if (previousTabIsPrivate && !extension.privateBrowsingAllowed) {
+          previousTabId = undefined;
+        }
+        fire.async({ tabId, previousTabId, windowId });
+      },
+    }),
+    onAttached: this.tabEventRegistrar({
+      event: "tab-attached",
+      listener: (fire, event) => {
+        fire.async(event.tabId, {
+          newWindowId: event.newWindowId,
+          newPosition: event.newPosition,
+        });
+      },
+    }),
+    onCreated: this.tabEventRegistrar({
+      event: "tab-created",
+      listener: (fire, event) => {
+        let { tabManager } = this.extension;
+        fire.async(tabManager.convert(event.nativeTab, event.currentTabSize));
+      },
+    }),
+    onDetached: this.tabEventRegistrar({
+      event: "tab-detached",
+      listener: (fire, event) => {
+        fire.async(event.tabId, {
+          oldWindowId: event.oldWindowId,
+          oldPosition: event.oldPosition,
+        });
+      },
+    }),
+    onRemoved: this.tabEventRegistrar({
+      event: "tab-removed",
+      listener: (fire, event) => {
+        fire.async(event.tabId, {
+          windowId: event.windowId,
+          isWindowClosing: event.isWindowClosing,
+        });
+      },
+    }),
+    onMoved({ fire }) {
+      let { tabManager } = this.extension;
+      let moveListener = event => {
+        let nativeTab = event.originalTarget;
+        if (tabManager.canAccessTab(nativeTab)) {
+          fire.async(tabTracker.getId(nativeTab), {
+            windowId: windowTracker.getId(nativeTab.ownerGlobal),
+            fromIndex: event.detail,
+            toIndex: nativeTab._tPos,
+          });
+        }
+      };
+
+      windowTracker.addListener("TabMove", moveListener);
+      return {
+        unregister() {
+          windowTracker.removeListener("TabMove", moveListener);
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+
+    onHighlighted({ fire, context }) {
+      let { windowManager } = this.extension;
+      let highlightListener = (eventName, event) => {
+        // TODO see if we can avoid "context" here
+        let window = windowTracker.getWindow(event.windowId, context, false);
+        if (!window) {
+          return;
+        }
+        let windowWrapper = windowManager.getWrapper(window);
+        if (!windowWrapper) {
+          return;
+        }
+        let tabIds = Array.from(
+          windowWrapper.getHighlightedTabs(),
+          tab => tab.id
+        );
+        fire.async({ tabIds: tabIds, windowId: event.windowId });
+      };
+
+      tabTracker.on("tabs-highlighted", highlightListener);
+      return {
+        unregister() {
+          tabTracker.off("tabs-highlighted", highlightListener);
+        },
+        convert(_fire, _context) {
+          fire = _fire;
+          context = _context;
+        },
+      };
+    },
+
+    onUpdated({ fire, context }, params) {
+      let { extension } = this;
+      let { tabManager } = extension;
+      let [filterProps] = params;
+      let filter = { ...filterProps };
+      if (filter.urls) {
+        filter.urls = new MatchPatternSet(filter.urls, {
+          restrictSchemes: false,
+        });
+      }
+      let needsModified = true;
+      if (filter.properties) {
+        // Default is to listen for all events.
+        needsModified = filter.properties.some(p => allAttrs.has(p));
+        filter.properties = new Set(filter.properties);
+      } else {
+        filter.properties = allProperties;
+      }
+
+      function sanitize(tab, changeInfo) {
+        let result = {};
+        let nonempty = false;
+        for (let prop in changeInfo) {
+          // In practice, changeInfo contains at most one property from
+          // restricted. Therefore it is not necessary to cache the value
+          // of tab.hasTabPermission outside the loop.
+          // Unnecessarily accessing tab.hasTabPermission can cause bugs, see
+          // https://bugzilla.mozilla.org/show_bug.cgi?id=1694699#c21
+          if (!restricted.has(prop) || tab.hasTabPermission) {
+            nonempty = true;
+            result[prop] = changeInfo[prop];
+          }
+        }
+        return nonempty && result;
+      }
+
+      function getWindowID(windowId) {
+        if (windowId === Window.WINDOW_ID_CURRENT) {
+          let window = windowTracker.getTopWindow(context);
+          if (!window) {
+            return undefined;
+          }
+          return windowTracker.getId(window);
+        }
+        return windowId;
+      }
+
+      function matchFilters(tab, changed) {
+        if (!filterProps) {
+          return true;
+        }
+        if (filter.tabId != null && tab.id != filter.tabId) {
+          return false;
+        }
+        if (
+          filter.windowId != null &&
+          tab.windowId != getWindowID(filter.windowId)
+        ) {
+          return false;
+        }
+        if (filter.urls) {
+          return filter.urls.matches(tab._uri) && tab.hasTabPermission;
+        }
+        return true;
+      }
+
+      let fireForTab = (tab, changed, nativeTab) => {
+        // Tab may be null if private and not_allowed.
+        if (!tab || !matchFilters(tab, changed)) {
+          return;
+        }
+
+        let changeInfo = sanitize(tab, changed);
+        if (changeInfo) {
+          tabTracker.maybeWaitForTabOpen(nativeTab).then(() => {
+            if (!nativeTab.parentNode) {
+              // If the tab is already be destroyed, do nothing.
+              return;
+            }
+            fire.async(tab.id, changeInfo, tab.convert());
+          });
+        }
+      };
+
+      let listener = event => {
+        // Ignore any events prior to TabOpen
+        // and events that are triggered while tabs are swapped between windows.
+        if (event.originalTarget.initializingTab) {
+          return;
+        }
+        if (!extension.canAccessWindow(event.originalTarget.ownerGlobal)) {
+          return;
+        }
+        let needed = [];
+        if (event.type == "TabAttrModified") {
+          let changed = event.detail.changed;
+          if (
+            changed.includes("image") &&
+            filter.properties.has("favIconUrl")
+          ) {
+            needed.push("favIconUrl");
+          }
+          if (changed.includes("muted") && filter.properties.has("mutedInfo")) {
+            needed.push("mutedInfo");
+          }
+          if (
+            changed.includes("soundplaying") &&
+            filter.properties.has("audible")
+          ) {
+            needed.push("audible");
+          }
+          if (changed.includes("label") && filter.properties.has("title")) {
+            needed.push("title");
+          }
+          if (
+            changed.includes("sharing") &&
+            filter.properties.has("sharingState")
+          ) {
+            needed.push("sharingState");
+          }
+          if (
+            changed.includes("attention") &&
+            filter.properties.has("attention")
+          ) {
+            needed.push("attention");
+          }
+        } else if (event.type == "TabPinned") {
+          needed.push("pinned");
+        } else if (event.type == "TabUnpinned") {
+          needed.push("pinned");
+        } else if (event.type == "TabBrowserInserted") {
+          // This may be an adopted tab. Bail early to avoid asking tabManager
+          // about the tab before we run the adoption logic in ext-browser.js.
+          if (event.detail.insertedOnTabCreation) {
+            return;
+          }
+          needed.push("discarded");
+        } else if (event.type == "TabBrowserDiscarded") {
+          needed.push("discarded");
+        } else if (event.type == "TabShow") {
+          needed.push("hidden");
+        } else if (event.type == "TabHide") {
+          needed.push("hidden");
+        }
+
+        let tab = tabManager.getWrapper(event.originalTarget);
+
+        let changeInfo = {};
+        for (let prop of needed) {
+          changeInfo[prop] = tab[prop];
+        }
+
+        fireForTab(tab, changeInfo, event.originalTarget);
+      };
+
+      let statusListener = ({ browser, status, url }) => {
+        let { gBrowser } = browser.ownerGlobal;
+        let tabElem = gBrowser.getTabForBrowser(browser);
+        if (tabElem) {
+          if (!extension.canAccessWindow(tabElem.ownerGlobal)) {
+            return;
+          }
+
+          let changed = {};
+          if (filter.properties.has("status")) {
+            changed.status = status;
+          }
+          if (url && filter.properties.has("url")) {
+            changed.url = url;
+          }
+
+          fireForTab(tabManager.wrapTab(tabElem), changed, tabElem);
+        }
+      };
+
+      let isArticleChangeListener = (messageName, message) => {
+        let { gBrowser } = message.target.ownerGlobal;
+        let nativeTab = gBrowser.getTabForBrowser(message.target);
+
+        if (nativeTab && extension.canAccessWindow(nativeTab.ownerGlobal)) {
+          let tab = tabManager.getWrapper(nativeTab);
+          fireForTab(tab, { isArticle: message.data.isArticle }, nativeTab);
+        }
+      };
+
+      let listeners = new Map();
+      if (filter.properties.has("status") || filter.properties.has("url")) {
+        listeners.set("status", statusListener);
+      }
+      if (needsModified) {
+        listeners.set("TabAttrModified", listener);
+      }
+      if (filter.properties.has("pinned")) {
+        listeners.set("TabPinned", listener);
+        listeners.set("TabUnpinned", listener);
+      }
+      if (filter.properties.has("discarded")) {
+        listeners.set("TabBrowserInserted", listener);
+        listeners.set("TabBrowserDiscarded", listener);
+      }
+      if (filter.properties.has("hidden")) {
+        listeners.set("TabShow", listener);
+        listeners.set("TabHide", listener);
+      }
+
+      for (let [name, listener] of listeners) {
+        windowTracker.addListener(name, listener);
+      }
+
+      if (filter.properties.has("isArticle")) {
+        tabTracker.on("tab-isarticle", isArticleChangeListener);
+      }
+
+      return {
+        unregister() {
+          for (let [name, listener] of listeners) {
+            windowTracker.removeListener(name, listener);
+          }
+
+          if (filter.properties.has("isArticle")) {
+            tabTracker.off("tab-isarticle", isArticleChangeListener);
+          }
+        },
+        convert(_fire, _context) {
+          fire = _fire;
+          context = _context;
+        },
+      };
+    },
+  };
+
+  getAPI(context) {
+    let { extension } = context;
+    let { tabManager, windowManager } = extension;
+    let extensionApi = this;
+    let module = "tabs";
+
+    function getTabOrActive(tabId) {
+      let tab =
+        tabId !== null ? tabTracker.getTab(tabId) : tabTracker.activeTab;
+      if (!tabManager.canAccessTab(tab)) {
+        throw new ExtensionError(
+          tabId === null
+            ? "Cannot access activeTab"
+            : `Invalid tab ID: ${tabId}`
+        );
+      }
+      return tab;
+    }
+
+    function getNativeTabsFromIDArray(tabIds) {
+      if (!Array.isArray(tabIds)) {
+        tabIds = [tabIds];
+      }
+      return tabIds.map(tabId => {
+        let tab = tabTracker.getTab(tabId);
+        if (!tabManager.canAccessTab(tab)) {
+          throw new ExtensionError(`Invalid tab ID: ${tabId}`);
+        }
+        return tab;
+      });
+    }
+
+    async function promiseTabWhenReady(tabId) {
+      let tab;
+      if (tabId !== null) {
+        tab = tabManager.get(tabId);
+      } else {
+        tab = tabManager.getWrapper(tabTracker.activeTab);
+      }
+      if (!tab) {
+        throw new ExtensionError(
+          tabId == null ? "Cannot access activeTab" : `Invalid tab ID: ${tabId}`
+        );
+      }
+
+      await tabListener.awaitTabReady(tab.nativeTab);
+
+      return tab;
+    }
+
+    function setContentTriggeringPrincipal(url, browser, options) {
+      // For urls that we want to allow an extension to open in a tab, but
+      // that it may not otherwise have access to, we set the triggering
+      // principal to the url that is being opened.  This is used for newtab,
+      // about: and moz-extension: protocols.
+      options.triggeringPrincipal =
+        Services.scriptSecurityManager.createContentPrincipal(
+          Services.io.newURI(url),
+          {
+            userContextId: options.userContextId,
+            privateBrowsingId: PrivateBrowsingUtils.isBrowserPrivate(browser)
+              ? 1
+              : 0,
+          }
+        );
+    }
+
+    let tabsApi = {
+      tabs: {
+        onActivated: new EventManager({
+          context,
+          module,
+          event: "onActivated",
+          extensionApi,
+        }).api(),
+
+        onCreated: new EventManager({
+          context,
+          module,
+          event: "onCreated",
+          extensionApi,
+        }).api(),
+
+        onHighlighted: new EventManager({
+          context,
+          module,
+          event: "onHighlighted",
+          extensionApi,
+        }).api(),
+
+        onAttached: new EventManager({
+          context,
+          module,
+          event: "onAttached",
+          extensionApi,
+        }).api(),
+
+        onDetached: new EventManager({
+          context,
+          module,
+          event: "onDetached",
+          extensionApi,
+        }).api(),
+
+        onRemoved: new EventManager({
+          context,
+          module,
+          event: "onRemoved",
+          extensionApi,
+        }).api(),
+
+        onReplaced: new EventManager({
+          context,
+          name: "tabs.onReplaced",
+          register: fire => {
+            return () => {};
+          },
+        }).api(),
+
+        onMoved: new EventManager({
+          context,
+          module,
+          event: "onMoved",
+          extensionApi,
+        }).api(),
+
+        onUpdated: new EventManager({
+          context,
+          module,
+          event: "onUpdated",
+          extensionApi,
+        }).api(),
+
+        create(createProperties) {
+          return new Promise((resolve, reject) => {
+            let window =
+              createProperties.windowId !== null
+                ? windowTracker.getWindow(createProperties.windowId, context)
+                : windowTracker.getTopNormalWindow(context);
+            if (!window || !context.canAccessWindow(window)) {
+              throw new Error(
+                "Not allowed to create tabs on the target window"
+              );
+            }
+            let { gBrowserInit } = window;
+            if (!gBrowserInit || !gBrowserInit.delayedStartupFinished) {
+              let obs = (finishedWindow, topic, data) => {
+                if (finishedWindow != window) {
+                  return;
+                }
+                Services.obs.removeObserver(
+                  obs,
+                  "browser-delayed-startup-finished"
+                );
+                resolve(window);
+              };
+              Services.obs.addObserver(obs, "browser-delayed-startup-finished");
+            } else {
+              resolve(window);
+            }
+          }).then(window => {
+            let url;
+
+            let options = { triggeringPrincipal: context.principal };
+            if (createProperties.cookieStoreId) {
+              // May throw if validation fails.
+              options.userContextId = getUserContextIdForCookieStoreId(
+                extension,
+                createProperties.cookieStoreId,
+                PrivateBrowsingUtils.isBrowserPrivate(window.gBrowser)
+              );
+            }
+
+            if (createProperties.url !== null) {
+              url = context.uri.resolve(createProperties.url);
+
+              if (
+                !url.startsWith("moz-extension://") &&
+                !context.checkLoadURL(url, { dontReportErrors: true })
+              ) {
+                return Promise.reject({ message: `Illegal URL: ${url}` });
+              }
+
+              if (createProperties.openInReaderMode) {
+                url = `about:reader?url=${encodeURIComponent(url)}`;
+              }
+            } else {
+              url = window.BROWSER_NEW_TAB_URL;
+            }
+            let discardable = url && !url.startsWith("about:");
+            // Handle moz-ext separately from the discardable flag to retain prior behavior.
+            if (!discardable || url.startsWith("moz-extension://")) {
+              setContentTriggeringPrincipal(url, window.gBrowser, options);
+            }
+
+            tabListener.initTabReady();
+            const currentTab = window.gBrowser.selectedTab;
+            const { frameLoader } = currentTab.linkedBrowser;
+            const currentTabSize = {
+              width: frameLoader.lazyWidth,
+              height: frameLoader.lazyHeight,
+            };
+
+            if (createProperties.openerTabId !== null) {
+              options.ownerTab = tabTracker.getTab(
+                createProperties.openerTabId
+              );
+              options.openerBrowser = options.ownerTab.linkedBrowser;
+              if (options.ownerTab.ownerGlobal !== window) {
+                return Promise.reject({
+                  message:
+                    "Opener tab must be in the same window as the tab being created",
+                });
+              }
+            }
+
+            // Simple properties
+            const properties = ["index", "pinned"];
+            for (let prop of properties) {
+              if (createProperties[prop] != null) {
+                options[prop] = createProperties[prop];
+              }
+            }
+
+            let active =
+              createProperties.active !== null
+                ? createProperties.active
+                : !createProperties.discarded;
+            if (createProperties.discarded) {
+              if (active) {
+                return Promise.reject({
+                  message: `Active tabs cannot be created and discarded.`,
+                });
+              }
+              if (createProperties.pinned) {
+                return Promise.reject({
+                  message: `Pinned tabs cannot be created and discarded.`,
+                });
+              }
+              if (!discardable) {
+                return Promise.reject({
+                  message: `Cannot create a discarded new tab or "about" urls.`,
+                });
+              }
+              options.createLazyBrowser = true;
+              options.lazyTabTitle = createProperties.title;
+            } else if (createProperties.title) {
+              return Promise.reject({
+                message: `Title may only be set for discarded tabs.`,
+              });
+            }
+
+            let nativeTab = window.gBrowser.addTab(url, options);
+
+            if (active) {
+              window.gBrowser.selectedTab = nativeTab;
+              if (!createProperties.url) {
+                window.gURLBar.select();
+              }
+            }
+
+            if (
+              createProperties.url &&
+              createProperties.url !== window.BROWSER_NEW_TAB_URL
+            ) {
+              // We can't wait for a location change event for about:newtab,
+              // since it may be pre-rendered, in which case its initial
+              // location change event has already fired.
+
+              // Mark the tab as initializing, so that operations like
+              // `executeScript` wait until the requested URL is loaded in
+              // the tab before dispatching messages to the inner window
+              // that contains the URL we're attempting to load.
+              tabListener.initializingTabs.add(nativeTab);
+            }
+
+            if (createProperties.muted) {
+              nativeTab.toggleMuteAudio(extension.id);
+            }
+
+            return tabManager.convert(nativeTab, currentTabSize);
+          });
+        },
+
+        async remove(tabIds) {
+          let nativeTabs = getNativeTabsFromIDArray(tabIds);
+
+          if (nativeTabs.length === 1) {
+            nativeTabs[0].ownerGlobal.gBrowser.removeTab(nativeTabs[0]);
+            return;
+          }
+
+          // Or for multiple tabs, first group them by window
+          let windowTabMap = new DefaultMap(() => []);
+          for (let nativeTab of nativeTabs) {
+            windowTabMap.get(nativeTab.ownerGlobal).push(nativeTab);
+          }
+
+          // Then make one call to removeTabs() for each window, to keep the
+          // count accurate for SessionStore.getLastClosedTabCount().
+          // Note: always pass options to disable animation and the warning
+          // dialogue box, so that way all tabs are actually closed when the
+          // browser.tabs.remove() promise resolves
+          for (let [eachWindow, tabsToClose] of windowTabMap.entries()) {
+            eachWindow.gBrowser.removeTabs(tabsToClose, {
+              animate: false,
+              suppressWarnAboutClosingWindow: true,
+            });
+          }
+        },
+
+        async discard(tabIds) {
+          for (let nativeTab of getNativeTabsFromIDArray(tabIds)) {
+            nativeTab.ownerGlobal.gBrowser.discardBrowser(nativeTab);
+          }
+        },
+
+        async update(tabId, updateProperties) {
+          let nativeTab = getTabOrActive(tabId);
+
+          let tabbrowser = nativeTab.ownerGlobal.gBrowser;
+
+          if (updateProperties.url !== null) {
+            let url = context.uri.resolve(updateProperties.url);
+
+            let options = {
+              flags: updateProperties.loadReplace
+                ? Ci.nsIWebNavigation.LOAD_FLAGS_REPLACE_HISTORY
+                : Ci.nsIWebNavigation.LOAD_FLAGS_NONE,
+              triggeringPrincipal: context.principal,
+            };
+
+            if (!context.checkLoadURL(url, { dontReportErrors: true })) {
+              // We allow loading top level tabs for "other" extensions.
+              if (url.startsWith("moz-extension://")) {
+                setContentTriggeringPrincipal(url, tabbrowser, options);
+              } else {
+                return Promise.reject({ message: `Illegal URL: ${url}` });
+              }
+            }
+
+            let browser = nativeTab.linkedBrowser;
+            if (nativeTab.linkedPanel) {
+              browser.fixupAndLoadURIString(url, options);
+            } else {
+              // Shift to fully loaded browser and make
+              // sure load handler is instantiated.
+              nativeTab.addEventListener(
+                "SSTabRestoring",
+                () => browser.fixupAndLoadURIString(url, options),
+                { once: true }
+              );
+              tabbrowser._insertBrowser(nativeTab);
+            }
+          }
+
+          if (updateProperties.active) {
+            tabbrowser.selectedTab = nativeTab;
+          }
+          if (updateProperties.highlighted !== null) {
+            if (updateProperties.highlighted) {
+              if (!nativeTab.selected && !nativeTab.multiselected) {
+                tabbrowser.addToMultiSelectedTabs(nativeTab);
+                // Select the highlighted tab unless active:false is provided.
+                // Note that Chrome selects it even in that case.
+                if (updateProperties.active !== false) {
+                  tabbrowser.lockClearMultiSelectionOnce();
+                  tabbrowser.selectedTab = nativeTab;
+                }
+              }
+            } else {
+              tabbrowser.removeFromMultiSelectedTabs(nativeTab);
+            }
+          }
+          if (updateProperties.muted !== null) {
+            if (nativeTab.muted != updateProperties.muted) {
+              nativeTab.toggleMuteAudio(extension.id);
+            }
+          }
+          if (updateProperties.pinned !== null) {
+            if (updateProperties.pinned) {
+              tabbrowser.pinTab(nativeTab);
+            } else {
+              tabbrowser.unpinTab(nativeTab);
+            }
+          }
+          if (updateProperties.openerTabId !== null) {
+            let opener = tabTracker.getTab(updateProperties.openerTabId);
+            if (opener.ownerDocument !== nativeTab.ownerDocument) {
+              return Promise.reject({
+                message:
+                  "Opener tab must be in the same window as the tab being updated",
+              });
+            }
+            tabTracker.setOpener(nativeTab, opener);
+          }
+          if (updateProperties.successorTabId !== null) {
+            let successor = null;
+            if (updateProperties.successorTabId !== TAB_ID_NONE) {
+              successor = tabTracker.getTab(
+                updateProperties.successorTabId,
+                null
+              );
+              if (!successor) {
+                throw new ExtensionError("Invalid successorTabId");
+              }
+              // This also ensures "privateness" matches.
+              if (successor.ownerDocument !== nativeTab.ownerDocument) {
+                throw new ExtensionError(
+                  "Successor tab must be in the same window as the tab being updated"
+                );
+              }
+            }
+            tabbrowser.setSuccessor(nativeTab, successor);
+          }
+
+          return tabManager.convert(nativeTab);
+        },
+
+        async reload(tabId, reloadProperties) {
+          let nativeTab = getTabOrActive(tabId);
+
+          let flags = Ci.nsIWebNavigation.LOAD_FLAGS_NONE;
+          if (reloadProperties && reloadProperties.bypassCache) {
+            flags |= Ci.nsIWebNavigation.LOAD_FLAGS_BYPASS_CACHE;
+          }
+          nativeTab.linkedBrowser.reloadWithFlags(flags);
+        },
+
+        async warmup(tabId) {
+          let nativeTab = tabTracker.getTab(tabId);
+          if (!tabManager.canAccessTab(nativeTab)) {
+            throw new ExtensionError(`Invalid tab ID: ${tabId}`);
+          }
+          let tabbrowser = nativeTab.ownerGlobal.gBrowser;
+          tabbrowser.warmupTab(nativeTab);
+        },
+
+        async get(tabId) {
+          return tabManager.get(tabId).convert();
+        },
+
+        getCurrent() {
+          let tabData;
+          if (context.tabId) {
+            tabData = tabManager.get(context.tabId).convert();
+          }
+          return Promise.resolve(tabData);
+        },
+
+        async query(queryInfo) {
+          return Array.from(tabManager.query(queryInfo, context), tab =>
+            tab.convert()
+          );
+        },
+
+        async captureTab(tabId, options) {
+          let nativeTab = getTabOrActive(tabId);
+          await tabListener.awaitTabReady(nativeTab);
+
+          let browser = nativeTab.linkedBrowser;
+          let window = browser.ownerGlobal;
+          let zoom = window.ZoomManager.getZoomForBrowser(browser);
+
+          let tab = tabManager.wrapTab(nativeTab);
+          return tab.capture(context, zoom, options);
+        },
+
+        async captureVisibleTab(windowId, options) {
+          let window =
+            windowId == null
+              ? windowTracker.getTopWindow(context)
+              : windowTracker.getWindow(windowId, context);
+
+          let tab = tabManager.wrapTab(window.gBrowser.selectedTab);
+          await tabListener.awaitTabReady(tab.nativeTab);
+
+          let zoom = window.ZoomManager.getZoomForBrowser(
+            tab.nativeTab.linkedBrowser
+          );
+          return tab.capture(context, zoom, options);
+        },
+
+        async detectLanguage(tabId) {
+          let tab = await promiseTabWhenReady(tabId);
+          let results = await tab.queryContent("DetectLanguage", {});
+          return results[0];
+        },
+
+        async executeScript(tabId, details) {
+          let tab = await promiseTabWhenReady(tabId);
+          return tab.executeScript(context, details);
+        },
+
+        async insertCSS(tabId, details) {
+          let tab = await promiseTabWhenReady(tabId);
+          return tab.insertCSS(context, details);
+        },
+
+        async removeCSS(tabId, details) {
+          let tab = await promiseTabWhenReady(tabId);
+          return tab.removeCSS(context, details);
+        },
+
+        async move(tabIds, moveProperties) {
+          let tabsMoved = [];
+          if (!Array.isArray(tabIds)) {
+            tabIds = [tabIds];
+          }
+
+          let destinationWindow = null;
+          if (moveProperties.windowId !== null) {
+            destinationWindow = windowTracker.getWindow(
+              moveProperties.windowId,
+              context
+            );
+            // Fail on an invalid window.
+            if (!destinationWindow) {
+              return Promise.reject({
+                message: `Invalid window ID: ${moveProperties.windowId}`,
+              });
+            }
+          }
+
+          /*
+            Indexes are maintained on a per window basis so that a call to
+              move([tabA, tabB], {index: 0})
+                -> tabA to 0, tabB to 1 if tabA and tabB are in the same window
+              move([tabA, tabB], {index: 0})
+                -> tabA to 0, tabB to 0 if tabA and tabB are in different windows
+          */
+          let lastInsertionMap = new Map();
+
+          for (let nativeTab of getNativeTabsFromIDArray(tabIds)) {
+            // If the window is not specified, use the window from the tab.
+            let window = destinationWindow || nativeTab.ownerGlobal;
+            let isSameWindow = nativeTab.ownerGlobal == window;
+            let gBrowser = window.gBrowser;
+
+            // If we are not moving the tab to a different window, and the window
+            // only has one tab, do nothing.
+            if (isSameWindow && gBrowser.tabs.length === 1) {
+              lastInsertionMap.set(window, 0);
+              continue;
+            }
+            // If moving between windows, be sure privacy matches.  While gBrowser
+            // prevents this, we want to silently ignore it.
+            if (
+              !isSameWindow &&
+              PrivateBrowsingUtils.isBrowserPrivate(gBrowser) !=
+                PrivateBrowsingUtils.isBrowserPrivate(
+                  nativeTab.ownerGlobal.gBrowser
+                )
+            ) {
+              continue;
+            }
+
+            let insertionPoint;
+            let lastInsertion = lastInsertionMap.get(window);
+            if (lastInsertion == null) {
+              insertionPoint = moveProperties.index;
+              let maxIndex = gBrowser.tabs.length - (isSameWindow ? 1 : 0);
+              if (insertionPoint == -1) {
+                // If the index is -1 it should go to the end of the tabs.
+                insertionPoint = maxIndex;
+              } else {
+                insertionPoint = Math.min(insertionPoint, maxIndex);
+              }
+            } else if (isSameWindow && nativeTab._tPos <= lastInsertion) {
+              // lastInsertion is the current index of the last inserted tab.
+              // insertionPoint is the desired index of the current tab *after* moving it.
+              // When the tab is moved, the last inserted tab will no longer be at index
+              // lastInsertion, but (lastInsertion - 1). To position the tabs adjacent to
+              // each other, the tab should therefore be at index (lastInsertion - 1 + 1).
+              insertionPoint = lastInsertion;
+            } else {
+              // In this case the last inserted tab will stay at index lastInsertion,
+              // so we should move the current tab to index (lastInsertion + 1).
+              insertionPoint = lastInsertion + 1;
+            }
+
+            // We can only move pinned tabs to a point within, or just after,
+            // the current set of pinned tabs. Unpinned tabs, likewise, can only
+            // be moved to a position after the current set of pinned tabs.
+            // Attempts to move a tab to an illegal position are ignored.
+            let numPinned = gBrowser._numPinnedTabs;
+            let ok = nativeTab.pinned
+              ? insertionPoint <= numPinned
+              : insertionPoint >= numPinned;
+            if (!ok) {
+              continue;
+            }
+
+            if (isSameWindow) {
+              // If the window we are moving is the same, just move the tab.
+              gBrowser.moveTabTo(nativeTab, insertionPoint);
+            } else {
+              // If the window we are moving the tab in is different, then move the tab
+              // to the new window.
+              nativeTab = gBrowser.adoptTab(nativeTab, insertionPoint, false);
+            }
+            lastInsertionMap.set(window, nativeTab._tPos);
+            tabsMoved.push(nativeTab);
+          }
+
+          return tabsMoved.map(nativeTab => tabManager.convert(nativeTab));
+        },
+
+        duplicate(tabId, duplicateProperties) {
+          const { active, index } = duplicateProperties || {};
+          const inBackground = active === undefined ? false : !active;
+
+          // Schema requires tab id.
+          let nativeTab = getTabOrActive(tabId);
+
+          let gBrowser = nativeTab.ownerGlobal.gBrowser;
+          let newTab = gBrowser.duplicateTab(nativeTab, true, {
+            inBackground,
+            index,
+          });
+
+          tabListener.blockTabUntilRestored(newTab);
+          return new Promise(resolve => {
+            // Use SSTabRestoring to ensure that the tab's URL is ready before
+            // resolving the promise.
+            newTab.addEventListener(
+              "SSTabRestoring",
+              () => resolve(tabManager.convert(newTab)),
+              { once: true }
+            );
+          });
+        },
+
+        getZoom(tabId) {
+          let nativeTab = getTabOrActive(tabId);
+
+          let { ZoomManager } = nativeTab.ownerGlobal;
+          let zoom = ZoomManager.getZoomForBrowser(nativeTab.linkedBrowser);
+
+          return Promise.resolve(zoom);
+        },
+
+        setZoom(tabId, zoom) {
+          let nativeTab = getTabOrActive(tabId);
+
+          let { FullZoom, ZoomManager } = nativeTab.ownerGlobal;
+
+          if (zoom === 0) {
+            // A value of zero means use the default zoom factor.
+            return FullZoom.reset(nativeTab.linkedBrowser);
+          } else if (zoom >= ZoomManager.MIN && zoom <= ZoomManager.MAX) {
+            FullZoom.setZoom(zoom, nativeTab.linkedBrowser);
+          } else {
+            return Promise.reject({
+              message: `Zoom value ${zoom} out of range (must be between ${ZoomManager.MIN} and ${ZoomManager.MAX})`,
+            });
+          }
+
+          return Promise.resolve();
+        },
+
+        async getZoomSettings(tabId) {
+          let nativeTab = getTabOrActive(tabId);
+
+          let { FullZoom, ZoomUI } = nativeTab.ownerGlobal;
+
+          return {
+            mode: "automatic",
+            scope: FullZoom.siteSpecific ? "per-origin" : "per-tab",
+            defaultZoomFactor: await ZoomUI.getGlobalValue(),
+          };
+        },
+
+        async setZoomSettings(tabId, settings) {
+          let nativeTab = getTabOrActive(tabId);
+
+          let currentSettings = await this.getZoomSettings(
+            tabTracker.getId(nativeTab)
+          );
+
+          if (
+            !Object.keys(settings).every(
+              key => settings[key] === currentSettings[key]
+            )
+          ) {
+            throw new ExtensionError(
+              `Unsupported zoom settings: ${JSON.stringify(settings)}`
+            );
+          }
+        },
+
+        onZoomChange: new EventManager({
+          context,
+          name: "tabs.onZoomChange",
+          register: fire => {
+            let getZoomLevel = browser => {
+              let { ZoomManager } = browser.ownerGlobal;
+
+              return ZoomManager.getZoomForBrowser(browser);
+            };
+
+            // Stores the last known zoom level for each tab's browser.
+            // WeakMap[<browser> -> number]
+            let zoomLevels = new WeakMap();
+
+            // Store the zoom level for all existing tabs.
+            for (let window of windowTracker.browserWindows()) {
+              if (!context.canAccessWindow(window)) {
+                continue;
+              }
+              for (let nativeTab of window.gBrowser.tabs) {
+                let browser = nativeTab.linkedBrowser;
+                zoomLevels.set(browser, getZoomLevel(browser));
+              }
+            }
+
+            let tabCreated = (eventName, event) => {
+              let browser = event.nativeTab.linkedBrowser;
+              if (!event.isPrivate || context.privateBrowsingAllowed) {
+                zoomLevels.set(browser, getZoomLevel(browser));
+              }
+            };
+
+            let zoomListener = async event => {
+              let browser = event.originalTarget;
+
+              // For non-remote browsers, this event is dispatched on the document
+              // rather than on the <browser>.  But either way we have a node here.
+              if (browser.nodeType == browser.DOCUMENT_NODE) {
+                browser = browser.docShell.chromeEventHandler;
+              }
+
+              if (!context.canAccessWindow(browser.ownerGlobal)) {
+                return;
+              }
+
+              let { gBrowser } = browser.ownerGlobal;
+              let nativeTab = gBrowser.getTabForBrowser(browser);
+              if (!nativeTab) {
+                // We only care about zoom events in the top-level browser of a tab.
+                return;
+              }
+
+              let oldZoomFactor = zoomLevels.get(browser);
+              let newZoomFactor = getZoomLevel(browser);
+
+              if (oldZoomFactor != newZoomFactor) {
+                zoomLevels.set(browser, newZoomFactor);
+
+                let tabId = tabTracker.getId(nativeTab);
+                fire.async({
+                  tabId,
+                  oldZoomFactor,
+                  newZoomFactor,
+                  zoomSettings: await tabsApi.tabs.getZoomSettings(tabId),
+                });
+              }
+            };
+
+            tabTracker.on("tab-attached", tabCreated);
+            tabTracker.on("tab-created", tabCreated);
+
+            windowTracker.addListener("FullZoomChange", zoomListener);
+            windowTracker.addListener("TextZoomChange", zoomListener);
+            return () => {
+              tabTracker.off("tab-attached", tabCreated);
+              tabTracker.off("tab-created", tabCreated);
+
+              windowTracker.removeListener("FullZoomChange", zoomListener);
+              windowTracker.removeListener("TextZoomChange", zoomListener);
+            };
+          },
+        }).api(),
+
+        print() {
+          let activeTab = getTabOrActive(null);
+          let { PrintUtils } = activeTab.ownerGlobal;
+          PrintUtils.startPrintWindow(activeTab.linkedBrowser.browsingContext);
+        },
+
+        // Legacy API
+        printPreview() {
+          return Promise.resolve(this.print());
+        },
+
+        saveAsPDF(pageSettings) {
+          let activeTab = getTabOrActive(null);
+          let picker = Cc["@mozilla.org/filepicker;1"].createInstance(
+            Ci.nsIFilePicker
+          );
+          let title = strBundle.GetStringFromName(
+            "saveaspdf.saveasdialog.title"
+          );
+          let filename;
+          if (
+            pageSettings.toFileName !== null &&
+            pageSettings.toFileName != ""
+          ) {
+            filename = pageSettings.toFileName;
+          } else if (activeTab.linkedBrowser.contentTitle != "") {
+            filename = activeTab.linkedBrowser.contentTitle;
+          } else {
+            let url = new URL(activeTab.linkedBrowser.currentURI.spec);
+            let path = decodeURIComponent(url.pathname);
+            path = path.replace(/\/$/, "");
+            filename = path.split("/").pop();
+            if (filename == "") {
+              filename = url.hostname;
+            }
+          }
+          filename = DownloadPaths.sanitize(filename);
+
+          picker.init(activeTab.ownerGlobal, title, Ci.nsIFilePicker.modeSave);
+          picker.appendFilter("PDF", "*.pdf");
+          picker.defaultExtension = "pdf";
+          picker.defaultString = filename;
+
+          return new Promise(resolve => {
+            picker.open(function (retval) {
+              if (retval == 0 || retval == 2) {
+                // OK clicked (retval == 0) or replace confirmed (retval == 2)
+
+                // Workaround: When trying to replace an existing file that is open in another application (i.e. a locked file),
+                // the print progress listener is never called. This workaround ensures that a correct status is always returned.
+                try {
+                  let fstream = Cc[
+                    "@mozilla.org/network/file-output-stream;1"
+                  ].createInstance(Ci.nsIFileOutputStream);
+                  fstream.init(picker.file, 0x2a, 0o666, 0); // ioflags = write|create|truncate, file permissions = rw-rw-rw-
+                  fstream.close();
+                } catch (e) {
+                  resolve(retval == 0 ? "not_saved" : "not_replaced");
+                  return;
+                }
+
+                let psService = Cc[
+                  "@mozilla.org/gfx/printsettings-service;1"
+                ].getService(Ci.nsIPrintSettingsService);
+                let printSettings = psService.createNewPrintSettings();
+
+                printSettings.printerName = "";
+                printSettings.isInitializedFromPrinter = true;
+                printSettings.isInitializedFromPrefs = true;
+
+                printSettings.outputDestination =
+                  Ci.nsIPrintSettings.kOutputDestinationFile;
+                printSettings.toFileName = picker.file.path;
+
+                printSettings.printSilent = true;
+
+                printSettings.outputFormat =
+                  Ci.nsIPrintSettings.kOutputFormatPDF;
+
+                if (pageSettings.paperSizeUnit !== null) {
+                  printSettings.paperSizeUnit = pageSettings.paperSizeUnit;
+                }
+                if (pageSettings.paperWidth !== null) {
+                  printSettings.paperWidth = pageSettings.paperWidth;
+                }
+                if (pageSettings.paperHeight !== null) {
+                  printSettings.paperHeight = pageSettings.paperHeight;
+                }
+                if (pageSettings.orientation !== null) {
+                  printSettings.orientation = pageSettings.orientation;
+                }
+                if (pageSettings.scaling !== null) {
+                  printSettings.scaling = pageSettings.scaling;
+                }
+                if (pageSettings.shrinkToFit !== null) {
+                  printSettings.shrinkToFit = pageSettings.shrinkToFit;
+                }
+                if (pageSettings.showBackgroundColors !== null) {
+                  printSettings.printBGColors =
+                    pageSettings.showBackgroundColors;
+                }
+                if (pageSettings.showBackgroundImages !== null) {
+                  printSettings.printBGImages =
+                    pageSettings.showBackgroundImages;
+                }
+                if (pageSettings.edgeLeft !== null) {
+                  printSettings.edgeLeft = pageSettings.edgeLeft;
+                }
+                if (pageSettings.edgeRight !== null) {
+                  printSettings.edgeRight = pageSettings.edgeRight;
+                }
+                if (pageSettings.edgeTop !== null) {
+                  printSettings.edgeTop = pageSettings.edgeTop;
+                }
+                if (pageSettings.edgeBottom !== null) {
+                  printSettings.edgeBottom = pageSettings.edgeBottom;
+                }
+                if (pageSettings.marginLeft !== null) {
+                  printSettings.marginLeft = pageSettings.marginLeft;
+                }
+                if (pageSettings.marginRight !== null) {
+                  printSettings.marginRight = pageSettings.marginRight;
+                }
+                if (pageSettings.marginTop !== null) {
+                  printSettings.marginTop = pageSettings.marginTop;
+                }
+                if (pageSettings.marginBottom !== null) {
+                  printSettings.marginBottom = pageSettings.marginBottom;
+                }
+                if (pageSettings.headerLeft !== null) {
+                  printSettings.headerStrLeft = pageSettings.headerLeft;
+                }
+                if (pageSettings.headerCenter !== null) {
+                  printSettings.headerStrCenter = pageSettings.headerCenter;
+                }
+                if (pageSettings.headerRight !== null) {
+                  printSettings.headerStrRight = pageSettings.headerRight;
+                }
+                if (pageSettings.footerLeft !== null) {
+                  printSettings.footerStrLeft = pageSettings.footerLeft;
+                }
+                if (pageSettings.footerCenter !== null) {
+                  printSettings.footerStrCenter = pageSettings.footerCenter;
+                }
+                if (pageSettings.footerRight !== null) {
+                  printSettings.footerStrRight = pageSettings.footerRight;
+                }
+
+                activeTab.linkedBrowser.browsingContext
+                  .print(printSettings)
+                  .then(() => resolve(retval == 0 ? "saved" : "replaced"))
+                  .catch(() =>
+                    resolve(retval == 0 ? "not_saved" : "not_replaced")
+                  );
+              } else {
+                // Cancel clicked (retval == 1)
+                resolve("canceled");
+              }
+            });
+          });
+        },
+
+        async toggleReaderMode(tabId) {
+          let tab = await promiseTabWhenReady(tabId);
+          if (!tab.isInReaderMode && !tab.isArticle) {
+            throw new ExtensionError(
+              "The specified tab cannot be placed into reader mode."
+            );
+          }
+          let nativeTab = getTabOrActive(tabId);
+
+          nativeTab.linkedBrowser.sendMessageToActor(
+            "Reader:ToggleReaderMode",
+            {},
+            "AboutReader"
+          );
+        },
+
+        moveInSuccession(tabIds, tabId, options) {
+          const { insert, append } = options || {};
+          const tabIdSet = new Set(tabIds);
+          if (tabIdSet.size !== tabIds.length) {
+            throw new ExtensionError(
+              "IDs must not occur more than once in tabIds"
+            );
+          }
+          if ((append || insert) && tabIdSet.has(tabId)) {
+            throw new ExtensionError(
+              "Value of tabId must not occur in tabIds if append or insert is true"
+            );
+          }
+
+          const referenceTab = tabTracker.getTab(tabId, null);
+          let referenceWindow = referenceTab && referenceTab.ownerGlobal;
+          if (referenceWindow && !context.canAccessWindow(referenceWindow)) {
+            throw new ExtensionError(`Invalid tab ID: ${tabId}`);
+          }
+          let previousTab, lastSuccessor;
+          if (append) {
+            previousTab = referenceTab;
+            lastSuccessor =
+              (insert && referenceTab && referenceTab.successor) || null;
+          } else {
+            lastSuccessor = referenceTab;
+          }
+
+          let firstTab;
+          for (const tabId of tabIds) {
+            const tab = tabTracker.getTab(tabId, null);
+            if (tab === null) {
+              continue;
+            }
+            if (!tabManager.canAccessTab(tab)) {
+              throw new ExtensionError(`Invalid tab ID: ${tabId}`);
+            }
+            if (referenceWindow === null) {
+              referenceWindow = tab.ownerGlobal;
+            } else if (tab.ownerGlobal !== referenceWindow) {
+              continue;
+            }
+            referenceWindow.gBrowser.replaceInSuccession(tab, tab.successor);
+            if (append && tab === lastSuccessor) {
+              lastSuccessor = tab.successor;
+            }
+            if (previousTab) {
+              referenceWindow.gBrowser.setSuccessor(previousTab, tab);
+            } else {
+              firstTab = tab;
+            }
+            previousTab = tab;
+          }
+
+          if (previousTab) {
+            if (!append && insert && lastSuccessor !== null) {
+              referenceWindow.gBrowser.replaceInSuccession(
+                lastSuccessor,
+                firstTab
+              );
+            }
+            referenceWindow.gBrowser.setSuccessor(previousTab, lastSuccessor);
+          }
+        },
+
+        show(tabIds) {
+          for (let tab of getNativeTabsFromIDArray(tabIds)) {
+            if (tab.ownerGlobal) {
+              tab.ownerGlobal.gBrowser.showTab(tab);
+            }
+          }
+        },
+
+        hide(tabIds) {
+          let hidden = [];
+          for (let tab of getNativeTabsFromIDArray(tabIds)) {
+            if (tab.ownerGlobal && !tab.hidden) {
+              tab.ownerGlobal.gBrowser.hideTab(tab, extension.id);
+              if (tab.hidden) {
+                hidden.push(tabTracker.getId(tab));
+              }
+            }
+          }
+          if (hidden.length) {
+            let win = Services.wm.getMostRecentWindow("navigator:browser");
+            tabHidePopup.open(win, extension.id);
+          }
+          return hidden;
+        },
+
+        highlight(highlightInfo) {
+          let { windowId, tabs, populate } = highlightInfo;
+          if (windowId == null) {
+            windowId = Window.WINDOW_ID_CURRENT;
+          }
+          let window = windowTracker.getWindow(windowId, context);
+          if (!context.canAccessWindow(window)) {
+            throw new ExtensionError(`Invalid window ID: ${windowId}`);
+          }
+
+          if (!Array.isArray(tabs)) {
+            tabs = [tabs];
+          } else if (!tabs.length) {
+            throw new ExtensionError("No highlighted tab.");
+          }
+          window.gBrowser.selectedTabs = tabs.map(tabIndex => {
+            let tab = window.gBrowser.tabs[tabIndex];
+            if (!tab || !tabManager.canAccessTab(tab)) {
+              throw new ExtensionError("No tab at index: " + tabIndex);
+            }
+            return tab;
+          });
+          return windowManager.convert(window, { populate });
+        },
+
+        goForward(tabId) {
+          let nativeTab = getTabOrActive(tabId);
+          nativeTab.linkedBrowser.goForward();
+        },
+
+        goBack(tabId) {
+          let nativeTab = getTabOrActive(tabId);
+          nativeTab.linkedBrowser.goBack();
+        },
+      },
+    };
+    return tabsApi;
+  }
+};
diff --git a/browser/components/extensions/parent/ext-topSites.js b/browser/components/extensions/parent/ext-topSites.js
new file mode 100644
index 0000000000..76a815f1ef
--- /dev/null
+++ b/browser/components/extensions/parent/ext-topSites.js
@@ -0,0 +1,120 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  NewTabUtils: "resource://gre/modules/NewTabUtils.sys.mjs",
+  getSearchProvider: "resource://activity-stream/lib/SearchShortcuts.sys.mjs",
+});
+
+XPCOMUtils.defineLazyModuleGetters(this, {
+  AboutNewTab: "resource:///modules/AboutNewTab.jsm",
+  shortURL: "resource://activity-stream/lib/ShortURL.jsm",
+});
+
+const SHORTCUTS_PREF =
+  "browser.newtabpage.activity-stream.improvesearch.topSiteSearchShortcuts";
+const TOPSITES_FEED_PREF =
+  "browser.newtabpage.activity-stream.feeds.system.topsites";
+
+this.topSites = class extends ExtensionAPI {
+  getAPI(context) {
+    return {
+      topSites: {
+        get: async function (options) {
+          // We fallback to newtab = false behavior if the user disabled their
+          // Top Sites feed.
+          let getNewtabSites =
+            options.newtab &&
+            Services.prefs.getBoolPref(TOPSITES_FEED_PREF, false);
+          let links = getNewtabSites
+            ? AboutNewTab.getTopSites()
+            : await NewTabUtils.activityStreamLinks.getTopSites({
+                ignoreBlocked: options.includeBlocked,
+                onePerDomain: options.onePerDomain,
+                numItems: options.limit,
+                includeFavicon: options.includeFavicon,
+              });
+
+          if (options.includePinned && !getNewtabSites) {
+            let pinnedLinks = NewTabUtils.pinnedLinks.links;
+            if (options.includeFavicon) {
+              pinnedLinks =
+                NewTabUtils.activityStreamProvider._faviconBytesToDataURI(
+                  await NewTabUtils.activityStreamProvider._addFavicons(
+                    pinnedLinks
+                  )
+                );
+            }
+            pinnedLinks.forEach((pinnedLink, index) => {
+              if (
+                pinnedLink &&
+                (!pinnedLink.searchTopSite || options.includeSearchShortcuts)
+              ) {
+                // Remove any dupes from history.
+                links = links.filter(
+                  link =>
+                    link.url != pinnedLink.url &&
+                    (!options.onePerDomain ||
+                      NewTabUtils.extractSite(link.url) !=
+                        pinnedLink.baseDomain)
+                );
+                links.splice(index, 0, pinnedLink);
+              }
+            });
+          }
+
+          // Convert links to search shortcuts, if necessary.
+          if (
+            options.includeSearchShortcuts &&
+            Services.prefs.getBoolPref(SHORTCUTS_PREF, false) &&
+            !getNewtabSites
+          ) {
+            // Pinned shortcuts are already returned as searchTopSite links,
+            // with a proper label and url. But certain non-pinned links may
+            // also be promoted to search shortcuts; here we convert them.
+            links = links.map(link => {
+              let searchProvider = getSearchProvider(shortURL(link));
+              if (searchProvider) {
+                link.searchTopSite = true;
+                link.label = searchProvider.keyword;
+                link.url = searchProvider.url;
+              }
+              return link;
+            });
+          }
+
+          // Because we may have added links, we must crop again.
+          if (typeof options.limit == "number") {
+            links = links.slice(0, options.limit);
+          }
+
+          const makeDataURI = url => url && ExtensionUtils.makeDataURI(url);
+
+          return Promise.all(
+            links.map(async link => ({
+              type: link.searchTopSite ? "search" : "url",
+              url: link.url,
+              // The newtab page allows the user to set custom site titles, which
+              // are stored in `label`, so prefer it.  Search top sites currently
+              // don't have titles but `hostname` instead.
+              title: link.label || link.title || link.hostname || "",
+              // Default top sites don't have a favicon property.  Instead they
+              // have tippyTopIcon, a 96x96pt image used on the newtab page.
+              // We'll use it as the favicon for now, but ideally default top
+              // sites would have real favicons.  Non-default top sites (i.e.,
+              // those from the user's history) will have favicons.
+              favicon: options.includeFavicon
+                ? link.favicon || (await makeDataURI(link.tippyTopIcon)) || null
+                : null,
+            }))
+          );
+        },
+      },
+    };
+  }
+};
diff --git a/browser/components/extensions/parent/ext-url-overrides.js b/browser/components/extensions/parent/ext-url-overrides.js
new file mode 100644
index 0000000000..07e35441ef
--- /dev/null
+++ b/browser/components/extensions/parent/ext-url-overrides.js
@@ -0,0 +1,210 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var { ExtensionParent } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionParent.sys.mjs"
+);
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionControlledPopup:
+    "resource:///modules/ExtensionControlledPopup.sys.mjs",
+  ExtensionSettingsStore:
+    "resource://gre/modules/ExtensionSettingsStore.sys.mjs",
+});
+ChromeUtils.defineModuleGetter(
+  this,
+  "AboutNewTab",
+  "resource:///modules/AboutNewTab.jsm"
+);
+
+const STORE_TYPE = "url_overrides";
+const NEW_TAB_SETTING_NAME = "newTabURL";
+const NEW_TAB_CONFIRMED_TYPE = "newTabNotification";
+const NEW_TAB_PRIVATE_ALLOWED = "browser.newtab.privateAllowed";
+const NEW_TAB_EXTENSION_CONTROLLED = "browser.newtab.extensionControlled";
+
+XPCOMUtils.defineLazyGetter(this, "newTabPopup", () => {
+  return new ExtensionControlledPopup({
+    confirmedType: NEW_TAB_CONFIRMED_TYPE,
+    observerTopic: "browser-open-newtab-start",
+    popupnotificationId: "extension-new-tab-notification",
+    settingType: STORE_TYPE,
+    settingKey: NEW_TAB_SETTING_NAME,
+    descriptionId: "extension-new-tab-notification-description",
+    descriptionMessageId: "newTabControlled.message2",
+    learnMoreMessageId: "newTabControlled.learnMore",
+    learnMoreLink: "extension-home",
+    preferencesLocation: "home-newtabOverride",
+    preferencesEntrypoint: "addon-manage-newtab-override",
+    onObserverAdded() {
+      AboutNewTab.willNotifyUser = true;
+    },
+    onObserverRemoved() {
+      AboutNewTab.willNotifyUser = false;
+    },
+    async beforeDisableAddon(popup, win) {
+      // ExtensionControlledPopup will disable the add-on once this function completes.
+      // Disabling an add-on should remove the tabs that it has open, but we want
+      // to open the new New Tab in this tab (which might get closed).
+      //   1. Replace the tab's URL with about:blank
+      //   2. Return control to ExtensionControlledPopup once about:blank has loaded
+      //   3. Once the New Tab URL has changed, replace the tab's URL with the new New Tab URL
+      let gBrowser = win.gBrowser;
+      let tab = gBrowser.selectedTab;
+      await replaceUrlInTab(gBrowser, tab, Services.io.newURI("about:blank"));
+      Services.obs.addObserver(
+        {
+          async observe() {
+            await replaceUrlInTab(
+              gBrowser,
+              tab,
+              Services.io.newURI(AboutNewTab.newTabURL)
+            );
+            // Now that the New Tab is loading, try to open the popup again. This
+            // will only open the popup if a new extension is controlling the New Tab.
+            popup.open();
+            Services.obs.removeObserver(this, "newtab-url-changed");
+          },
+        },
+        "newtab-url-changed"
+      );
+    },
+  });
+});
+
+function setNewTabURL(extensionId, url) {
+  if (extensionId) {
+    newTabPopup.addObserver(extensionId);
+    let policy = ExtensionParent.WebExtensionPolicy.getByID(extensionId);
+    Services.prefs.setBoolPref(
+      NEW_TAB_PRIVATE_ALLOWED,
+      policy && policy.privateBrowsingAllowed
+    );
+    Services.prefs.setBoolPref(NEW_TAB_EXTENSION_CONTROLLED, true);
+  } else {
+    newTabPopup.removeObserver();
+    Services.prefs.clearUserPref(NEW_TAB_PRIVATE_ALLOWED);
+    Services.prefs.clearUserPref(NEW_TAB_EXTENSION_CONTROLLED);
+  }
+  if (url) {
+    AboutNewTab.newTabURL = url;
+  }
+}
+
+// eslint-disable-next-line mozilla/balanced-listeners
+ExtensionParent.apiManager.on(
+  "extension-setting-changed",
+  async (eventName, setting) => {
+    let extensionId, url;
+    if (setting.type === STORE_TYPE && setting.key === NEW_TAB_SETTING_NAME) {
+      // If the actual setting has changed in some way, we will have
+      // setting.item which is what the setting has been changed to.  If
+      // we have an item, we always want to update the newTabUrl values.
+      let { item } = setting;
+      if (item) {
+        // If we're resetting, id will be undefined.
+        extensionId = item.id;
+        url = item.value || item.initialValue;
+        setNewTabURL(extensionId, url);
+      }
+    }
+  }
+);
+
+async function processSettings(action, id) {
+  await ExtensionSettingsStore.initialize();
+  if (ExtensionSettingsStore.hasSetting(id, STORE_TYPE, NEW_TAB_SETTING_NAME)) {
+    ExtensionSettingsStore[action](id, STORE_TYPE, NEW_TAB_SETTING_NAME);
+  }
+}
+
+this.urlOverrides = class extends ExtensionAPI {
+  static async onDisable(id) {
+    newTabPopup.clearConfirmation(id);
+    await processSettings("disable", id);
+  }
+
+  static async onEnabling(id) {
+    await processSettings("enable", id);
+  }
+
+  static async onUninstall(id) {
+    // TODO: This can be removed once bug 1438364 is fixed and all data is cleaned up.
+    newTabPopup.clearConfirmation(id);
+    await processSettings("removeSetting", id);
+  }
+
+  static async onUpdate(id, manifest) {
+    if (
+      !manifest.chrome_url_overrides ||
+      !manifest.chrome_url_overrides.newtab
+    ) {
+      await ExtensionSettingsStore.initialize();
+      if (
+        ExtensionSettingsStore.hasSetting(id, STORE_TYPE, NEW_TAB_SETTING_NAME)
+      ) {
+        ExtensionSettingsStore.removeSetting(
+          id,
+          STORE_TYPE,
+          NEW_TAB_SETTING_NAME
+        );
+      }
+    }
+  }
+
+  async onManifestEntry(entryName) {
+    let { extension } = this;
+    let { manifest } = extension;
+
+    if (manifest.chrome_url_overrides.newtab) {
+      let url = extension.baseURI.resolve(manifest.chrome_url_overrides.newtab);
+
+      await ExtensionSettingsStore.initialize();
+      let item = await ExtensionSettingsStore.addSetting(
+        extension.id,
+        STORE_TYPE,
+        NEW_TAB_SETTING_NAME,
+        url,
+        () => AboutNewTab.newTabURL
+      );
+
+      // Set the newTabURL to the current value of the setting.
+      if (item) {
+        setNewTabURL(item.id, item.value || item.initialValue);
+      }
+
+      // We need to monitor permission change and update the preferences.
+      // eslint-disable-next-line mozilla/balanced-listeners
+      extension.on("add-permissions", async (ignoreEvent, permissions) => {
+        if (
+          permissions.permissions.includes("internal:privateBrowsingAllowed")
+        ) {
+          let item = await ExtensionSettingsStore.getSetting(
+            STORE_TYPE,
+            NEW_TAB_SETTING_NAME
+          );
+          if (item && item.id == extension.id) {
+            Services.prefs.setBoolPref(NEW_TAB_PRIVATE_ALLOWED, true);
+          }
+        }
+      });
+      // eslint-disable-next-line mozilla/balanced-listeners
+      extension.on("remove-permissions", async (ignoreEvent, permissions) => {
+        if (
+          permissions.permissions.includes("internal:privateBrowsingAllowed")
+        ) {
+          let item = await ExtensionSettingsStore.getSetting(
+            STORE_TYPE,
+            NEW_TAB_SETTING_NAME
+          );
+          if (item && item.id == extension.id) {
+            Services.prefs.setBoolPref(NEW_TAB_PRIVATE_ALLOWED, false);
+          }
+        }
+      });
+    }
+  }
+};
diff --git a/browser/components/extensions/parent/ext-urlbar.js b/browser/components/extensions/parent/ext-urlbar.js
new file mode 100644
index 0000000000..1632558461
--- /dev/null
+++ b/browser/components/extensions/parent/ext-urlbar.js
@@ -0,0 +1,153 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  UrlbarPrefs: "resource:///modules/UrlbarPrefs.sys.mjs",
+  UrlbarProviderExtension:
+    "resource:///modules/UrlbarProviderExtension.sys.mjs",
+});
+
+var { ExtensionPreferencesManager } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionPreferencesManager.sys.mjs"
+);
+var { getSettingsAPI } = ExtensionPreferencesManager;
+
+ExtensionPreferencesManager.addSetting("engagementTelemetry", {
+  prefNames: ["browser.urlbar.eventTelemetry.enabled"],
+  setCallback(value) {
+    return { [this.prefNames[0]]: value };
+  },
+});
+
+this.urlbar = class extends ExtensionAPI {
+  getAPI(context) {
+    return {
+      urlbar: {
+        closeView() {
+          let window = windowTracker.getTopNormalWindow(context);
+          window.gURLBar.view.close();
+        },
+
+        focus(select = false) {
+          let window = windowTracker.getTopNormalWindow(context);
+          if (select) {
+            window.gURLBar.select();
+          } else {
+            window.gURLBar.focus();
+          }
+        },
+
+        search(searchString, options = {}) {
+          let window = windowTracker.getTopNormalWindow(context);
+          window.gURLBar.search(searchString, options);
+        },
+
+        onBehaviorRequested: new EventManager({
+          context,
+          name: "urlbar.onBehaviorRequested",
+          register: (fire, providerName) => {
+            let provider = UrlbarProviderExtension.getOrCreate(providerName);
+            provider.setEventListener(
+              "behaviorRequested",
+              async queryContext => {
+                if (queryContext.isPrivate && !context.privateBrowsingAllowed) {
+                  return "inactive";
+                }
+                return fire.async(queryContext).catch(error => {
+                  throw context.normalizeError(error);
+                });
+              }
+            );
+            return () => provider.setEventListener("behaviorRequested", null);
+          },
+        }).api(),
+
+        onEngagement: new EventManager({
+          context,
+          name: "urlbar.onEngagement",
+          register: (fire, providerName) => {
+            let provider = UrlbarProviderExtension.getOrCreate(providerName);
+            provider.setEventListener(
+              "engagement",
+              async (isPrivate, state) => {
+                if (isPrivate && !context.privateBrowsingAllowed) {
+                  return;
+                }
+                return fire.async(state).catch(error => {
+                  throw context.normalizeError(error);
+                });
+              }
+            );
+            return () => provider.setEventListener("engagement", null);
+          },
+        }).api(),
+
+        onQueryCanceled: new EventManager({
+          context,
+          name: "urlbar.onQueryCanceled",
+          register: (fire, providerName) => {
+            let provider = UrlbarProviderExtension.getOrCreate(providerName);
+            provider.setEventListener("queryCanceled", async queryContext => {
+              if (queryContext.isPrivate && !context.privateBrowsingAllowed) {
+                return;
+              }
+              await fire.async(queryContext).catch(error => {
+                throw context.normalizeError(error);
+              });
+            });
+            return () => provider.setEventListener("queryCanceled", null);
+          },
+        }).api(),
+
+        onResultsRequested: new EventManager({
+          context,
+          name: "urlbar.onResultsRequested",
+          register: (fire, providerName) => {
+            let provider = UrlbarProviderExtension.getOrCreate(providerName);
+            provider.setEventListener(
+              "resultsRequested",
+              async queryContext => {
+                if (queryContext.isPrivate && !context.privateBrowsingAllowed) {
+                  return [];
+                }
+                return fire.async(queryContext).catch(error => {
+                  throw context.normalizeError(error);
+                });
+              }
+            );
+            return () => provider.setEventListener("resultsRequested", null);
+          },
+        }).api(),
+
+        onResultPicked: new EventManager({
+          context,
+          name: "urlbar.onResultPicked",
+          inputHandling: true,
+          register: (fire, providerName) => {
+            let provider = UrlbarProviderExtension.getOrCreate(providerName);
+            provider.setEventListener(
+              "resultPicked",
+              async (resultPayload, dynamicElementName) => {
+                return fire
+                  .async(resultPayload, dynamicElementName)
+                  .catch(error => {
+                    throw context.normalizeError(error);
+                  });
+              }
+            );
+            return () => provider.setEventListener("resultPicked", null);
+          },
+        }).api(),
+
+        engagementTelemetry: getSettingsAPI({
+          context,
+          name: "engagementTelemetry",
+          callback: () => UrlbarPrefs.get("eventTelemetry.enabled"),
+        }),
+      },
+    };
+  }
+};
diff --git a/browser/components/extensions/parent/ext-windows.js b/browser/components/extensions/parent/ext-windows.js
new file mode 100644
index 0000000000..37c837b99e
--- /dev/null
+++ b/browser/components/extensions/parent/ext-windows.js
@@ -0,0 +1,548 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+ChromeUtils.defineModuleGetter(
+  this,
+  "HomePage",
+  "resource:///modules/HomePage.jsm"
+);
+ChromeUtils.defineESModuleGetters(this, {
+  PrivateBrowsingUtils: "resource://gre/modules/PrivateBrowsingUtils.sys.mjs",
+});
+
+var { ExtensionError, promiseObserved } = ExtensionUtils;
+
+function sanitizePositionParams(params, window = null, positionOffset = 0) {
+  if (params.left === null && params.top === null) {
+    return;
+  }
+
+  if (params.left === null) {
+    const baseLeft = window ? window.screenX : 0;
+    params.left = baseLeft + positionOffset;
+  }
+  if (params.top === null) {
+    const baseTop = window ? window.screenY : 0;
+    params.top = baseTop + positionOffset;
+  }
+
+  // boundary check: don't put window out of visible area
+  const baseWidth = window ? window.outerWidth : 0;
+  const baseHeight = window ? window.outerHeight : 0;
+  // Secure minimum size of an window should be same to the one
+  // defined at nsGlobalWindowOuter::CheckSecurityWidthAndHeight.
+  const minWidth = 100;
+  const minHeight = 100;
+  const width = Math.max(
+    minWidth,
+    params.width !== null ? params.width : baseWidth
+  );
+  const height = Math.max(
+    minHeight,
+    params.height !== null ? params.height : baseHeight
+  );
+  const screenManager = Cc["@mozilla.org/gfx/screenmanager;1"].getService(
+    Ci.nsIScreenManager
+  );
+  const screen = screenManager.screenForRect(
+    params.left,
+    params.top,
+    width,
+    height
+  );
+  const availDeviceLeft = {};
+  const availDeviceTop = {};
+  const availDeviceWidth = {};
+  const availDeviceHeight = {};
+  screen.GetAvailRect(
+    availDeviceLeft,
+    availDeviceTop,
+    availDeviceWidth,
+    availDeviceHeight
+  );
+  const slopX = window?.screenEdgeSlopX || 0;
+  const slopY = window?.screenEdgeSlopY || 0;
+  const factor = screen.defaultCSSScaleFactor;
+  const availLeft = Math.floor(availDeviceLeft.value / factor) - slopX;
+  const availTop = Math.floor(availDeviceTop.value / factor) - slopY;
+  const availWidth = Math.floor(availDeviceWidth.value / factor) + slopX;
+  const availHeight = Math.floor(availDeviceHeight.value / factor) + slopY;
+  params.left = Math.min(
+    availLeft + availWidth - width,
+    Math.max(availLeft, params.left)
+  );
+  params.top = Math.min(
+    availTop + availHeight - height,
+    Math.max(availTop, params.top)
+  );
+}
+
+this.windows = class extends ExtensionAPIPersistent {
+  windowEventRegistrar(event, listener) {
+    let { extension } = this;
+    return ({ fire }) => {
+      let listener2 = (window, ...args) => {
+        if (extension.canAccessWindow(window)) {
+          listener(fire, window, ...args);
+        }
+      };
+
+      windowTracker.addListener(event, listener2);
+      return {
+        unregister() {
+          windowTracker.removeListener(event, listener2);
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    };
+  }
+
+  PERSISTENT_EVENTS = {
+    onCreated: this.windowEventRegistrar("domwindowopened", (fire, window) => {
+      fire.async(this.extension.windowManager.convert(window));
+    }),
+    onRemoved: this.windowEventRegistrar("domwindowclosed", (fire, window) => {
+      fire.async(windowTracker.getId(window));
+    }),
+    onFocusChanged({ fire }) {
+      let { extension } = this;
+      // Keep track of the last windowId used to fire an onFocusChanged event
+      let lastOnFocusChangedWindowId;
+
+      let listener = event => {
+        // Wait a tick to avoid firing a superfluous WINDOW_ID_NONE
+        // event when switching focus between two Firefox windows.
+        Promise.resolve().then(() => {
+          let windowId = Window.WINDOW_ID_NONE;
+          let window = Services.focus.activeWindow;
+          if (window && extension.canAccessWindow(window)) {
+            windowId = windowTracker.getId(window);
+          }
+          if (windowId !== lastOnFocusChangedWindowId) {
+            fire.async(windowId);
+            lastOnFocusChangedWindowId = windowId;
+          }
+        });
+      };
+      windowTracker.addListener("focus", listener);
+      windowTracker.addListener("blur", listener);
+      return {
+        unregister() {
+          windowTracker.removeListener("focus", listener);
+          windowTracker.removeListener("blur", listener);
+        },
+        convert(_fire) {
+          fire = _fire;
+        },
+      };
+    },
+  };
+
+  getAPI(context) {
+    let { extension } = context;
+
+    const { windowManager } = extension;
+
+    return {
+      windows: {
+        onCreated: new EventManager({
+          context,
+          module: "windows",
+          event: "onCreated",
+          extensionApi: this,
+        }).api(),
+
+        onRemoved: new EventManager({
+          context,
+          module: "windows",
+          event: "onRemoved",
+          extensionApi: this,
+        }).api(),
+
+        onFocusChanged: new EventManager({
+          context,
+          module: "windows",
+          event: "onFocusChanged",
+          extensionApi: this,
+        }).api(),
+
+        get: function (windowId, getInfo) {
+          let window = windowTracker.getWindow(windowId, context);
+          if (!window || !context.canAccessWindow(window)) {
+            return Promise.reject({
+              message: `Invalid window ID: ${windowId}`,
+            });
+          }
+          return Promise.resolve(windowManager.convert(window, getInfo));
+        },
+
+        getCurrent: function (getInfo) {
+          let window = context.currentWindow || windowTracker.topWindow;
+          if (!context.canAccessWindow(window)) {
+            return Promise.reject({ message: `Invalid window` });
+          }
+          return Promise.resolve(windowManager.convert(window, getInfo));
+        },
+
+        getLastFocused: function (getInfo) {
+          let window = windowTracker.topWindow;
+          if (!context.canAccessWindow(window)) {
+            return Promise.reject({ message: `Invalid window` });
+          }
+          return Promise.resolve(windowManager.convert(window, getInfo));
+        },
+
+        getAll: function (getInfo) {
+          let doNotCheckTypes =
+            getInfo === null || getInfo.windowTypes === null;
+          let windows = [];
+          // incognito access is checked in getAll
+          for (let win of windowManager.getAll()) {
+            if (doNotCheckTypes || getInfo.windowTypes.includes(win.type)) {
+              windows.push(win.convert(getInfo));
+            }
+          }
+          return windows;
+        },
+
+        create: async function (createData) {
+          let needResize =
+            createData.left !== null ||
+            createData.top !== null ||
+            createData.width !== null ||
+            createData.height !== null;
+          if (createData.incognito && !context.privateBrowsingAllowed) {
+            throw new ExtensionError(
+              "Extension does not have permission for incognito mode"
+            );
+          }
+
+          if (needResize) {
+            if (createData.state !== null && createData.state != "normal") {
+              throw new ExtensionError(
+                `"state": "${createData.state}" may not be combined with "left", "top", "width", or "height"`
+              );
+            }
+            createData.state = "normal";
+          }
+
+          function mkstr(s) {
+            let result = Cc["@mozilla.org/supports-string;1"].createInstance(
+              Ci.nsISupportsString
+            );
+            result.data = s;
+            return result;
+          }
+
+          let args = Cc["@mozilla.org/array;1"].createInstance(
+            Ci.nsIMutableArray
+          );
+
+          // Whether there is only one URL to load, and it is a moz-extension:-URL.
+          let isOnlyMozExtensionUrl = false;
+
+          // Creating a new window allows one single triggering principal for all tabs that
+          // are created in the window.  Due to that, if we need a browser principal to load
+          // some urls, we fallback to using a content principal like we do in the tabs api.
+          // Throws if url is an array and any url can't be loaded by the extension principal.
+          let principal = context.principal;
+          function setContentTriggeringPrincipal(url) {
+            principal = Services.scriptSecurityManager.createContentPrincipal(
+              Services.io.newURI(url),
+              {
+                // Note: privateBrowsingAllowed was already checked before.
+                privateBrowsingId: createData.incognito ? 1 : 0,
+              }
+            );
+          }
+
+          if (createData.tabId !== null) {
+            if (createData.url !== null) {
+              throw new ExtensionError(
+                "`tabId` may not be used in conjunction with `url`"
+              );
+            }
+
+            if (createData.allowScriptsToClose) {
+              throw new ExtensionError(
+                "`tabId` may not be used in conjunction with `allowScriptsToClose`"
+              );
+            }
+
+            let tab = tabTracker.getTab(createData.tabId);
+            if (!context.canAccessWindow(tab.ownerGlobal)) {
+              throw new ExtensionError(`Invalid tab ID: ${createData.tabId}`);
+            }
+            // Private browsing tabs can only be moved to private browsing
+            // windows.
+            let incognito = PrivateBrowsingUtils.isBrowserPrivate(
+              tab.linkedBrowser
+            );
+            if (
+              createData.incognito !== null &&
+              createData.incognito != incognito
+            ) {
+              throw new ExtensionError(
+                "`incognito` property must match the incognito state of tab"
+              );
+            }
+            createData.incognito = incognito;
+
+            if (
+              createData.cookieStoreId &&
+              createData.cookieStoreId !==
+                getCookieStoreIdForTab(createData, tab)
+            ) {
+              throw new ExtensionError(
+                "`cookieStoreId` must match the tab's cookieStoreId"
+              );
+            }
+
+            args.appendElement(tab);
+          } else if (createData.url !== null) {
+            if (Array.isArray(createData.url)) {
+              let array = Cc["@mozilla.org/array;1"].createInstance(
+                Ci.nsIMutableArray
+              );
+              for (let url of createData.url.map(u => context.uri.resolve(u))) {
+                // We can only provide a single triggering principal when
+                // opening a window, so if the extension cannot normally
+                // access a url, we fail.  This includes about and moz-ext
+                // urls.
+                if (!context.checkLoadURL(url, { dontReportErrors: true })) {
+                  return Promise.reject({ message: `Illegal URL: ${url}` });
+                }
+                array.appendElement(mkstr(url));
+              }
+              args.appendElement(array);
+              // TODO bug 1780583: support multiple triggeringPrincipals to
+              // avoid having to use the system principal here.
+              principal = Services.scriptSecurityManager.getSystemPrincipal();
+            } else {
+              let url = context.uri.resolve(createData.url);
+              args.appendElement(mkstr(url));
+              isOnlyMozExtensionUrl = url.startsWith("moz-extension://");
+              if (!context.checkLoadURL(url, { dontReportErrors: true })) {
+                if (isOnlyMozExtensionUrl) {
+                  // For backwards-compatibility (also in tabs APIs), we allow
+                  // extensions to open other moz-extension:-URLs even if that
+                  // other resource is not listed in web_accessible_resources.
+                  setContentTriggeringPrincipal(url);
+                } else {
+                  throw new ExtensionError(`Illegal URL: ${url}`);
+                }
+              }
+            }
+          } else {
+            let url =
+              createData.incognito &&
+              !PrivateBrowsingUtils.permanentPrivateBrowsing
+                ? "about:privatebrowsing"
+                : HomePage.get().split("|", 1)[0];
+            args.appendElement(mkstr(url));
+            isOnlyMozExtensionUrl = url.startsWith("moz-extension://");
+
+            if (!context.checkLoadURL(url, { dontReportErrors: true })) {
+              // The extension principal cannot directly load about:-URLs,
+              // except for about:blank, or other moz-extension:-URLs that are
+              // not in web_accessible_resources. Ensure any page set as a home
+              // page will load by using a content principal.
+              setContentTriggeringPrincipal(url);
+            }
+          }
+
+          args.appendElement(null); // extraOptions
+          args.appendElement(null); // referrerInfo
+          args.appendElement(null); // postData
+          args.appendElement(null); // allowThirdPartyFixup
+
+          if (createData.cookieStoreId) {
+            let userContextIdSupports = Cc[
+              "@mozilla.org/supports-PRUint32;1"
+            ].createInstance(Ci.nsISupportsPRUint32);
+            // May throw if validation fails.
+            userContextIdSupports.data = getUserContextIdForCookieStoreId(
+              extension,
+              createData.cookieStoreId,
+              createData.incognito
+            );
+
+            args.appendElement(userContextIdSupports); // userContextId
+          } else {
+            args.appendElement(null);
+          }
+
+          args.appendElement(context.principal); // originPrincipal - not important.
+          args.appendElement(context.principal); // originStoragePrincipal - not important.
+          args.appendElement(principal); // triggeringPrincipal
+          args.appendElement(
+            Cc["@mozilla.org/supports-PRBool;1"].createInstance(
+              Ci.nsISupportsPRBool
+            )
+          ); // allowInheritPrincipal
+          // There is no CSP associated with this extension, hence we explicitly pass null as the CSP argument.
+          args.appendElement(null); // csp
+
+          let features = ["chrome"];
+
+          if (createData.type === null || createData.type == "normal") {
+            features.push("dialog=no", "all");
+          } else {
+            // All other types create "popup"-type windows by default.
+            features.push(
+              "dialog",
+              "resizable",
+              "minimizable",
+              "titlebar",
+              "close"
+            );
+            if (createData.left === null && createData.top === null) {
+              features.push("centerscreen");
+            }
+          }
+
+          if (createData.incognito !== null) {
+            if (createData.incognito) {
+              if (!PrivateBrowsingUtils.enabled) {
+                throw new ExtensionError(
+                  "`incognito` cannot be used if incognito mode is disabled"
+                );
+              }
+              features.push("private");
+            } else {
+              features.push("non-private");
+            }
+          }
+
+          const baseWindow = windowTracker.getTopNormalWindow(context);
+          // 10px offset is same to Chromium
+          sanitizePositionParams(createData, baseWindow, 10);
+
+          let window = Services.ww.openWindow(
+            null,
+            AppConstants.BROWSER_CHROME_URL,
+            "_blank",
+            features.join(","),
+            args
+          );
+
+          let win = windowManager.getWrapper(window);
+          win.updateGeometry(createData);
+
+          // TODO: focused, type
+
+          const contentLoaded = new Promise(resolve => {
+            window.addEventListener(
+              "DOMContentLoaded",
+              function () {
+                let { allowScriptsToClose } = createData;
+                if (allowScriptsToClose === null && isOnlyMozExtensionUrl) {
+                  allowScriptsToClose = true;
+                }
+                if (allowScriptsToClose) {
+                  window.gBrowserAllowScriptsToCloseInitialTabs = true;
+                }
+                resolve();
+              },
+              { once: true }
+            );
+          });
+
+          const startupFinished = promiseObserved(
+            "browser-delayed-startup-finished",
+            win => win == window
+          );
+
+          await contentLoaded;
+          await startupFinished;
+
+          if (
+            [
+              "minimized",
+              "fullscreen",
+              "docked",
+              "normal",
+              "maximized",
+            ].includes(createData.state)
+          ) {
+            await win.setState(createData.state);
+          }
+
+          if (createData.titlePreface !== null) {
+            win.setTitlePreface(createData.titlePreface);
+          }
+          return win.convert({ populate: true });
+        },
+
+        update: async function (windowId, updateInfo) {
+          if (updateInfo.state !== null && updateInfo.state != "normal") {
+            if (
+              updateInfo.left !== null ||
+              updateInfo.top !== null ||
+              updateInfo.width !== null ||
+              updateInfo.height !== null
+            ) {
+              throw new ExtensionError(
+                `"state": "${updateInfo.state}" may not be combined with "left", "top", "width", or "height"`
+              );
+            }
+          }
+
+          let win = windowManager.get(windowId, context);
+          if (!win) {
+            throw new ExtensionError(`Invalid window ID: ${windowId}`);
+          }
+          if (updateInfo.focused) {
+            win.window.focus();
+          }
+
+          if (updateInfo.state !== null) {
+            await win.setState(updateInfo.state);
+          }
+
+          if (updateInfo.drawAttention) {
+            // Bug 1257497 - Firefox can't cancel attention actions.
+            win.window.getAttention();
+          }
+
+          sanitizePositionParams(updateInfo, win.window);
+          win.updateGeometry(updateInfo);
+
+          if (updateInfo.titlePreface !== null) {
+            win.setTitlePreface(updateInfo.titlePreface);
+            win.window.gBrowser.updateTitlebar();
+          }
+
+          // TODO: All the other properties, focused=false...
+
+          return win.convert();
+        },
+
+        remove: function (windowId) {
+          let window = windowTracker.getWindow(windowId, context);
+          if (!context.canAccessWindow(window)) {
+            return Promise.reject({
+              message: `Invalid window ID: ${windowId}`,
+            });
+          }
+          window.close();
+
+          return new Promise(resolve => {
+            let listener = () => {
+              windowTracker.removeListener("domwindowclosed", listener);
+              resolve();
+            };
+            windowTracker.addListener("domwindowclosed", listener);
+          });
+        },
+      },
+    };
+  }
+};