--- a/accessible/jsat/ContentControl.jsm
+++ b/accessible/jsat/ContentControl.jsm
@@ -1,13 +1,12 @@
 /* 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/. */
 
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "Utils",
   "resource://gre/modules/accessibility/Utils.jsm");
 ChromeUtils.defineModuleGetter(this, "Logger",
   "resource://gre/modules/accessibility/Utils.jsm");
 ChromeUtils.defineModuleGetter(this, "Roles",
   "resource://gre/modules/accessibility/Constants.jsm");
 ChromeUtils.defineModuleGetter(this, "States",
   "resource://gre/modules/accessibility/Constants.jsm");

--- a/accessible/jsat/EventManager.jsm
+++ b/accessible/jsat/EventManager.jsm
@@ -1,15 +1,14 @@
 /* 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.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "Services",
   "resource://gre/modules/Services.jsm");
 ChromeUtils.defineModuleGetter(this, "Utils",
   "resource://gre/modules/accessibility/Utils.jsm");
 ChromeUtils.defineModuleGetter(this, "Logger",
   "resource://gre/modules/accessibility/Utils.jsm");
 ChromeUtils.defineModuleGetter(this, "Presentation",
   "resource://gre/modules/accessibility/Presentation.jsm");

--- a/accessible/jsat/Traversal.jsm
+++ b/accessible/jsat/Traversal.jsm
@@ -1,20 +1,17 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-/* exported TraversalRules, TraversalHelper */
-
 "use strict";
 
 var EXPORTED_SYMBOLS = ["TraversalRules", "TraversalHelper"]; // jshint ignore:line
 
 ChromeUtils.import("resource://gre/modules/accessibility/Utils.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "Roles", // jshint ignore:line
   "resource://gre/modules/accessibility/Constants.jsm");
 ChromeUtils.defineModuleGetter(this, "Filters", // jshint ignore:line
   "resource://gre/modules/accessibility/Constants.jsm");
 ChromeUtils.defineModuleGetter(this, "States", // jshint ignore:line
   "resource://gre/modules/accessibility/Constants.jsm");
 ChromeUtils.defineModuleGetter(this, "Prefilters", // jshint ignore:line
   "resource://gre/modules/accessibility/Constants.jsm");

--- a/accessible/jsat/Utils.jsm
+++ b/accessible/jsat/Utils.jsm
@@ -1,17 +1,14 @@
 /* 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/. */
 
-/* exported Utils, Logger, PivotContext, PrefCache */
-
 "use strict";
 
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "Services", // jshint ignore:line
   "resource://gre/modules/Services.jsm");
 ChromeUtils.defineModuleGetter(this, "Rect", // jshint ignore:line
   "resource://gre/modules/Geometry.jsm");
 ChromeUtils.defineModuleGetter(this, "Roles", // jshint ignore:line
   "resource://gre/modules/accessibility/Constants.jsm");
 ChromeUtils.defineModuleGetter(this, "Events", // jshint ignore:line
   "resource://gre/modules/accessibility/Constants.jsm");

--- a/browser/app/profile/firefox.js
+++ b/browser/app/profile/firefox.js
@@ -466,17 +466,17 @@ pref("browser.tabs.extraDragSpace", fals
 // true   return to the tab that opened this tab (its owner)
 // false  return to the adjacent tab (old default)
 pref("browser.tabs.selectOwnerOnClose", true);
 
 pref("browser.tabs.showAudioPlayingIcon", true);
 // This should match Chromium's audio indicator delay.
 pref("browser.tabs.delayHidingAudioPlayingIconMS", 3000);
 
-pref("browser.ctrlTab.previews", false);
+pref("browser.ctrlTab.recentlyUsedOrder", true);
 
 // By default, do not export HTML at shutdown.
 // If true, at shutdown the bookmarks in your menu and toolbar will
 // be exported as HTML to the bookmarks.html file.
 pref("browser.bookmarks.autoExportHTML",          false);
 
 // The maximum number of daily bookmark backups to
 // keep in {PROFILEDIR}/bookmarkbackups. Special values:
@@ -1142,17 +1142,17 @@ pref("services.sync.prefs.sync.accessibi
 pref("services.sync.prefs.sync.accessibility.typeaheadfind", true);
 pref("services.sync.prefs.sync.accessibility.typeaheadfind.linksonly", true);
 pref("services.sync.prefs.sync.addons.ignoreUserEnabledChanges", true);
 // The addons prefs related to repository verification are intentionally
 // not synced for security reasons. If a system is compromised, a user
 // could weaken the pref locally, install an add-on from an untrusted
 // source, and this would propagate automatically to other,
 // uncompromised Sync-connected devices.
-pref("services.sync.prefs.sync.browser.ctrlTab.previews", true);
+pref("services.sync.prefs.sync.browser.ctrlTab.recentlyUsedOrder", true);
 pref("services.sync.prefs.sync.browser.download.useDownloadDir", true);
 pref("services.sync.prefs.sync.browser.formfill.enable", true);
 pref("services.sync.prefs.sync.browser.link.open_newwindow", true);
 pref("services.sync.prefs.sync.browser.newtabpage.enabled", true);
 pref("services.sync.prefs.sync.browser.newtabpage.pinned", true);
 pref("services.sync.prefs.sync.browser.offline-apps.notify", true);
 pref("services.sync.prefs.sync.browser.safebrowsing.phishing.enabled", true);
 pref("services.sync.prefs.sync.browser.safebrowsing.malware.enabled", true);

--- a/browser/base/content/browser-ctrlTab.js
+++ b/browser/base/content/browser-ctrlTab.js
@@ -215,17 +215,17 @@ var ctrlTab = {
 
   uninit: function ctrlTab_uninit() {
     if (this._recentlyUsedTabs) {
       this._recentlyUsedTabs = null;
       this._init(false);
     }
   },
 
-  prefName: "browser.ctrlTab.previews",
+  prefName: "browser.ctrlTab.recentlyUsedOrder",
   readPref: function ctrlTab_readPref() {
     var enable =
       Services.prefs.getBoolPref(this.prefName) &&
       !Services.prefs.getBoolPref("browser.ctrlTab.disallowForScreenReaders", false);
 
     if (enable)
       this.init();
     else
@@ -460,58 +460,62 @@ var ctrlTab = {
   suspendGUI: function ctrlTab_suspendGUI() {
     document.removeEventListener("keyup", this, true);
 
     for (let preview of this.previews) {
       this.updatePreview(preview, null);
     }
   },
 
-  onKeyPress: function ctrlTab_onKeyPress(event) {
-    var isOpen = this.isOpen;
-
-    if (isOpen) {
-      event.preventDefault();
-      event.stopPropagation();
+  onKeyDown(event) {
+    if (event.keyCode != event.DOM_VK_TAB ||
+        !event.ctrlKey ||
+        event.altKey ||
+        event.metaKey) {
+      return;
     }
 
-    switch (event.keyCode) {
-      case event.DOM_VK_TAB:
-        if (event.ctrlKey && !event.altKey && !event.metaKey) {
-          if (isOpen) {
-            this.advanceFocus(!event.shiftKey);
-          } else if (!event.shiftKey) {
-            event.preventDefault();
-            event.stopPropagation();
-            let tabs = gBrowser.visibleTabs;
-            if (tabs.length > 2) {
-              this.open();
-            } else if (tabs.length == 2) {
-              let index = tabs[0].selected ? 1 : 0;
-              gBrowser.selectedTab = tabs[index];
-            }
-          }
-        }
+    event.preventDefault();
+    event.stopPropagation();
+
+    if (this.isOpen) {
+      this.advanceFocus(!event.shiftKey);
+    } else if (!event.shiftKey) {
+      let tabs = gBrowser.visibleTabs;
+      if (tabs.length > 2) {
+        this.open();
+      } else if (tabs.length == 2) {
+        let index = tabs[0].selected ? 1 : 0;
+        gBrowser.selectedTab = tabs[index];
+      }
+    }
+  },
+
+  onKeyPress(event) {
+    if (!this.isOpen ||
+        !event.ctrlKey) {
+      return;
+    }
+
+    event.preventDefault();
+    event.stopPropagation();
+
+    if (event.keyCode == event.DOM_VK_DELETE) {
+      this.remove(this.selected);
+      return;
+    }
+
+    switch (event.charCode) {
+      case this.keys.close:
+        this.remove(this.selected);
         break;
-      default:
-        if (isOpen && event.ctrlKey) {
-          if (event.keyCode == event.DOM_VK_DELETE) {
-            this.remove(this.selected);
-            break;
-          }
-          switch (event.charCode) {
-            case this.keys.close:
-              this.remove(this.selected);
-              break;
-            case this.keys.find:
-            case this.keys.selectAll:
-              this.showAllTabs();
-              break;
-          }
-        }
+      case this.keys.find:
+      case this.keys.selectAll:
+        this.showAllTabs();
+        break;
     }
   },
 
   removeClosingTabFromUI: function ctrlTab_removeClosingTabFromUI(aTab) {
     if (this.tabCount == 2) {
       this.close();
       return;
     }
@@ -556,16 +560,19 @@ var ctrlTab = {
       case "TabOpen":
         this.attachTab(event.target, 1);
         break;
       case "TabClose":
         this.detachTab(event.target);
         if (this.isOpen)
           this.removeClosingTabFromUI(event.target);
         break;
+      case "keydown":
+        this.onKeyDown(event);
+        break;
       case "keypress":
         this.onKeyPress(event);
         break;
       case "keyup":
         if (event.keyCode == event.DOM_VK_CONTROL)
           this.pick();
         break;
       case "popupshowing":
@@ -601,16 +608,21 @@ var ctrlTab = {
     window[toggleEventListener]("SSWindowRestored", this);
 
     var tabContainer = gBrowser.tabContainer;
     tabContainer[toggleEventListener]("TabOpen", this);
     tabContainer[toggleEventListener]("TabAttrModified", this);
     tabContainer[toggleEventListener]("TabSelect", this);
     tabContainer[toggleEventListener]("TabClose", this);
 
+    if (enable) {
+      Services.els.addSystemEventListener(document, "keydown", this, false);
+    } else {
+      Services.els.removeSystemEventListener(document, "keydown", this, false);
+    }
     document[toggleEventListener]("keypress", this);
     gBrowser.tabbox.handleCtrlTab = !enable;
 
     if (enable)
       PageThumbs.addExpirationFilter(this);
     else
       PageThumbs.removeExpirationFilter(this);
 

--- a/browser/base/content/browser.xul
+++ b/browser/base/content/browser.xul
@@ -794,17 +794,16 @@
                      placeholder="&urlbar.placeholder2;"
                      defaultPlaceholder="&urlbar.placeholder2;"
                      focused="true"
                      type="autocomplete"
                      autocompletesearch="unifiedcomplete"
                      autocompletesearchparam="enable-actions"
                      autocompletepopup="PopupAutoCompleteRichResult"
                      completeselectedindex="true"
-                     shrinkdelay="250"
                      tabscrolling="true"
                      newlines="stripsurroundingwhitespace"
                      ontextentered="this.handleCommand(param);"
                      ontextreverted="return this.handleRevert();"
                      pageproxystate="invalid">
               <!-- Use onclick instead of normal popup= syntax since the popup
                    code fires onmousedown, and hence eats our favicon drag events. -->
               <box id="identity-box" role="button"

--- a/browser/base/content/tabbrowser.js
+++ b/browser/base/content/tabbrowser.js
@@ -1272,47 +1272,49 @@ window._gBrowser = {
         // No suitable URI? Fall back to our untitled string.
         title = this.tabContainer.emptyTabTitle;
       }
     }
 
     return this._setTabLabel(aTab, title, { isContentTitle });
   },
 
-  _setTabLabel(aTab, aLabel, aOptions) {
+  _setTabLabel(aTab, aLabel, {
+    beforeTabOpen,
+    isContentTitle,
+  } = {}) {
     if (!aLabel) {
       return false;
     }
 
     aTab._fullLabel = aLabel;
 
-    aOptions = aOptions || {};
-    if (!aOptions.isContentTitle) {
+    if (!isContentTitle) {
       // Remove protocol and "www."
       if (!("_regex_shortenURLForTabLabel" in this)) {
         this._regex_shortenURLForTabLabel = /^[^:]+:\/\/(?:www\.)?/;
       }
       aLabel = aLabel.replace(this._regex_shortenURLForTabLabel, "");
     }
 
-    aTab._labelIsContentTitle = aOptions.isContentTitle;
+    aTab._labelIsContentTitle = isContentTitle;
 
     if (aTab.getAttribute("label") == aLabel) {
       return false;
     }
 
     let dwu = window.windowUtils;
     let isRTL = dwu.getDirectionFromText(aLabel) == Ci.nsIDOMWindowUtils.DIRECTION_RTL;
 
     aTab.setAttribute("label", aLabel);
     aTab.setAttribute("labeldirection", isRTL ? "rtl" : "ltr");
 
     // Dispatch TabAttrModified event unless we're setting the label
     // before the TabOpen event was dispatched.
-    if (!aOptions.beforeTabOpen) {
+    if (!beforeTabOpen) {
       this._tabAttrModified(aTab, ["label"]);
     }
 
     if (aTab.selected) {
       this.updateTitlebar();
     }
 
     return true;
@@ -1507,46 +1509,50 @@ window._gBrowser = {
       this.addTab(aURIs[i], params);
     }
 
     if (firstTabAdded && !aLoadInBackground) {
       this.selectedTab = firstTabAdded;
     }
   },
 
-  updateBrowserRemoteness(aBrowser, aShouldBeRemote, aOptions) {
-    aOptions = aOptions || {};
+  updateBrowserRemoteness(aBrowser, aShouldBeRemote, {
+    newFrameloader,
+    opener,
+    remoteType,
+    sameProcessAsFrameLoader,
+  } = {}) {
     let isRemote = aBrowser.getAttribute("remote") == "true";
 
     if (!gMultiProcessBrowser && aShouldBeRemote) {
       throw new Error("Cannot switch to remote browser in a window " +
         "without the remote tabs load context.");
     }
 
     // Default values for remoteType
-    if (!aOptions.remoteType) {
-      aOptions.remoteType = aShouldBeRemote ? E10SUtils.DEFAULT_REMOTE_TYPE : E10SUtils.NOT_REMOTE;
+    if (!remoteType) {
+      remoteType = aShouldBeRemote ? E10SUtils.DEFAULT_REMOTE_TYPE : E10SUtils.NOT_REMOTE;
     }
 
     // If we are passed an opener, we must be making the browser non-remote, and
     // if the browser is _currently_ non-remote, we need the openers to match,
     // because it is already too late to change it.
-    if (aOptions.opener) {
+    if (opener) {
       if (aShouldBeRemote) {
         throw new Error("Cannot set an opener on a browser which should be remote!");
       }
-      if (!isRemote && aBrowser.contentWindow.opener != aOptions.opener) {
+      if (!isRemote && aBrowser.contentWindow.opener != opener) {
         throw new Error("Cannot change opener on an already non-remote browser!");
       }
     }
 
     // Abort if we're not going to change anything
-    let currentRemoteType = aBrowser.getAttribute("remoteType");
-    if (isRemote == aShouldBeRemote && !aOptions.newFrameloader &&
-        (!isRemote || currentRemoteType == aOptions.remoteType)) {
+    let oldRemoteType = aBrowser.getAttribute("remoteType");
+    if (isRemote == aShouldBeRemote && !newFrameloader &&
+        (!isRemote || oldRemoteType == remoteType)) {
       return false;
     }
 
     let tab = this.getTabForBrowser(aBrowser);
     // aBrowser needs to be inserted now if it hasn't been already.
     this._insertBrowser(tab);
 
     let evt = document.createEvent("Events");
@@ -1562,63 +1568,60 @@ window._gBrowser = {
     let filter = this._tabFilters.get(tab);
     let listener = this._tabListeners.get(tab);
     aBrowser.webProgress.removeProgressListener(filter);
     filter.removeProgressListener(listener);
 
     // We'll be creating a new listener, so destroy the old one.
     listener.destroy();
 
+    let oldDroppedLinkHandler = aBrowser.droppedLinkHandler;
+    let oldSameProcessAsFrameLoader = aBrowser.sameProcessAsFrameLoader;
     let oldUserTypedValue = aBrowser.userTypedValue;
     let hadStartedLoad = aBrowser.didStartLoadSinceLastUserTyping();
 
     // Make sure the browser is destroyed so it unregisters from observer notifications
     aBrowser.destroy();
 
-    // Make sure to restore the original droppedLinkHandler and
-    // sameProcessAsFrameLoader.
-    let droppedLinkHandler = aBrowser.droppedLinkHandler;
-    let sameProcessAsFrameLoader = aBrowser.sameProcessAsFrameLoader;
-
     // Change the "remote" attribute.
     let parent = aBrowser.parentNode;
     aBrowser.remove();
     if (aShouldBeRemote) {
       aBrowser.setAttribute("remote", "true");
-      aBrowser.setAttribute("remoteType", aOptions.remoteType);
+      aBrowser.setAttribute("remoteType", remoteType);
     } else {
       aBrowser.setAttribute("remote", "false");
       aBrowser.removeAttribute("remoteType");
     }
 
     // NB: This works with the hack in the browser constructor that
     // turns this normal property into a field.
-    if (aOptions.sameProcessAsFrameLoader) {
-      // Always set sameProcessAsFrameLoader when passed in aOptions.
-      aBrowser.sameProcessAsFrameLoader = aOptions.sameProcessAsFrameLoader;
-    } else if (!aShouldBeRemote || currentRemoteType == aOptions.remoteType) {
+    if (sameProcessAsFrameLoader) {
+      // Always set sameProcessAsFrameLoader when passed in explicitly.
+      aBrowser.sameProcessAsFrameLoader = sameProcessAsFrameLoader;
+    } else if (!aShouldBeRemote || oldRemoteType == remoteType) {
       // Only copy existing sameProcessAsFrameLoader when not switching
       // remote type otherwise it would stop the switch.
-      aBrowser.sameProcessAsFrameLoader = sameProcessAsFrameLoader;
-    }
-
-    if (aOptions.opener) {
+      aBrowser.sameProcessAsFrameLoader = oldSameProcessAsFrameLoader;
+    }
+
+    if (opener) {
       // Set the opener window on the browser, such that when the frame
       // loader is created the opener is set correctly.
-      aBrowser.presetOpenerWindow(aOptions.opener);
+      aBrowser.presetOpenerWindow(opener);
     }
 
     parent.appendChild(aBrowser);
 
     aBrowser.userTypedValue = oldUserTypedValue;
     if (hadStartedLoad) {
       aBrowser.urlbarChangeTracker.startedLoad();
     }
 
-    aBrowser.droppedLinkHandler = droppedLinkHandler;
+    aBrowser.droppedLinkHandler = oldDroppedLinkHandler;
 
     // Switching a browser's remoteness will create a new frameLoader.
     // As frameLoaders start out with an active docShell we have to
     // deactivate it if this is not the selected tab's browser or the
     // browser window is minimized.
     aBrowser.docShellIsActive = this.shouldActivateDocShell(aBrowser);
 
     // Create a new tab progress listener for the new browser we just injected,
@@ -1673,28 +1676,28 @@ window._gBrowser = {
   },
 
   updateBrowserRemotenessByURL(aBrowser, aURL, aOptions) {
     aOptions = aOptions || {};
 
     if (!gMultiProcessBrowser)
       return this.updateBrowserRemoteness(aBrowser, false);
 
-    let currentRemoteType = aBrowser.getAttribute("remoteType") || null;
+    let oldRemoteType = aBrowser.getAttribute("remoteType") || null;
 
     aOptions.remoteType =
       E10SUtils.getRemoteTypeForURI(aURL,
         gMultiProcessBrowser,
-        currentRemoteType,
+        oldRemoteType,
         aBrowser.currentURI);
 
     // If this URL can't load in the current browser then flip it to the
     // correct type.
-    if (currentRemoteType != aOptions.remoteType ||
-      aOptions.newFrameloader) {
+    if (oldRemoteType != aOptions.remoteType ||
+        aOptions.newFrameloader) {
       let remote = aOptions.remoteType != E10SUtils.NOT_REMOTE;
       return this.updateBrowserRemoteness(aBrowser, remote, aOptions);
     }
 
     return false;
   },
 
   removePreloadedBrowser() {
@@ -1770,61 +1773,66 @@ window._gBrowser = {
     browser.docShellIsActive = false;
     browser._urlbarFocused = true;
 
     // Make sure the preloaded browser is loaded with desired zoom level
     let tabURI = Services.io.newURI(BROWSER_NEW_TAB_URL);
     FullZoom.onLocationChange(tabURI, false, browser);
   },
 
-  _createBrowser(aParams) {
-    // Supported parameters:
-    // userContextId, remote, remoteType, isPreloadBrowser,
-    // uriIsAboutBlank, sameProcessAsFrameLoader,
-    // recordExecution, replayExecution
-
+  _createBrowser({
+    isPreloadBrowser,
+    name,
+    nextTabParentId,
+    openerWindow,
+    recordExecution,
+    remote,
+    remoteType,
+    replayExecution,
+    sameProcessAsFrameLoader,
+    uriIsAboutBlank,
+    userContextId,
+  } = {}) {
     let b = document.createElementNS(this._XUL_NS, "browser");
     b.permanentKey = {};
 
     for (let attribute in this._defaultBrowserAttributes) {
       b.setAttribute(attribute, this._defaultBrowserAttributes[attribute]);
     }
 
-    if (aParams.userContextId) {
-      b.setAttribute("usercontextid", aParams.userContextId);
+    if (userContextId) {
+      b.setAttribute("usercontextid", userContextId);
     }
 
     // remote parameter used by some addons, use default in this case.
-    if (aParams.remote && !aParams.remoteType) {
-      aParams.remoteType = E10SUtils.DEFAULT_REMOTE_TYPE;
-    }
-
-    if (aParams.remoteType) {
-      b.setAttribute("remoteType", aParams.remoteType);
+    if (remote && !remoteType) {
+      remoteType = E10SUtils.DEFAULT_REMOTE_TYPE;
+    }
+
+    if (remoteType) {
+      b.setAttribute("remoteType", remoteType);
       b.setAttribute("remote", "true");
     }
 
-    let recordExecution = aParams && aParams.recordExecution;
     if (recordExecution) {
       b.setAttribute("recordExecution", recordExecution);
     }
 
-    let replayExecution = aParams && aParams.replayExecution;
     if (replayExecution) {
       b.setAttribute("replayExecution", replayExecution);
     }
 
-    if (aParams.openerWindow) {
-      if (aParams.remoteType) {
+    if (openerWindow) {
+      if (remoteType) {
         throw new Error("Cannot set opener window on a remote browser!");
       }
-      b.presetOpenerWindow(aParams.openerWindow);
-    }
-
-    if (!aParams.isPreloadBrowser) {
+      b.presetOpenerWindow(openerWindow);
+    }
+
+    if (!isPreloadBrowser) {
       b.setAttribute("autocompletepopup", "PopupAutoComplete");
     }
 
     /*
      * This attribute is meant to describe if the browser is the
      * preloaded browser. There are 2 defined states: "preloaded" or
      * "consumed". The order of events goes as follows:
      *   1. The preloaded browser is created and the 'preloadedState'
@@ -1833,38 +1841,38 @@ window._gBrowser = {
      *      preloaded browser, the 'preloadedState' attribute for that
      *      browser is set to "consumed"
      *   3. When we then navigate away from about:newtab, the "consumed"
      *      browsers will attempt to switch to a new content process,
      *      therefore the 'preloadedState' attribute is removed from
      *      that browser altogether
      * See more details on Bug 1420285.
      */
-    if (aParams.isPreloadBrowser) {
+    if (isPreloadBrowser) {
       b.setAttribute("preloadedState", "preloaded");
     }
 
-    if (aParams.nextTabParentId) {
-      if (!aParams.remoteType) {
+    if (nextTabParentId) {
+      if (!remoteType) {
         throw new Error("Cannot have nextTabParentId without a remoteType");
       }
       // Gecko is going to read this attribute and use it.
-      b.setAttribute("nextTabParentId", aParams.nextTabParentId.toString());
-    }
-
-    if (aParams.sameProcessAsFrameLoader) {
-      b.sameProcessAsFrameLoader = aParams.sameProcessAsFrameLoader;
+      b.setAttribute("nextTabParentId", nextTabParentId.toString());
+    }
+
+    if (sameProcessAsFrameLoader) {
+      b.sameProcessAsFrameLoader = sameProcessAsFrameLoader;
     }
 
     // This will be used by gecko to control the name of the opened
     // window.
-    if (aParams.name) {
+    if (name) {
       // XXX: The `name` property is special in HTML and XUL. Should
       // we use a different attribute name for this?
-      b.setAttribute("name", aParams.name);
+      b.setAttribute("name", name);
     }
 
     // Create the browserStack container
     let stack = document.createElementNS(this._XUL_NS, "stack");
     stack.className = "browserStack";
     stack.appendChild(b);
     stack.setAttribute("flex", "1");
 
@@ -1883,17 +1891,17 @@ window._gBrowser = {
     // Add the Message and the Browser to the box
     let notificationbox = document.createElementNS(this._XUL_NS, "notificationbox");
     notificationbox.setAttribute("flex", "1");
     notificationbox.setAttribute("notificationside", "top");
     notificationbox.appendChild(browserSidebarContainer);
 
     // Prevent the superfluous initial load of a blank document
     // if we're going to load something other than about:blank.
-    if (!aParams.uriIsAboutBlank) {
+    if (!uriIsAboutBlank) {
       b.setAttribute("nodefaultsrc", "true");
     }
 
     return b;
   },
 
   _createLazyBrowser(aTab) {
     let browser = aTab.linkedBrowser;
@@ -2608,23 +2616,21 @@ window._gBrowser = {
       this.removeTab(lastToClose, aParams);
     }
   },
 
   removeCurrentTab(aParams) {
     this.removeTab(this.selectedTab, aParams);
   },
 
-  removeTab(aTab, aParams) {
-    if (aParams) {
-      var animate = aParams.animate;
-      var byMouse = aParams.byMouse;
-      var skipPermitUnload = aParams.skipPermitUnload;
-    }
-
+  removeTab(aTab, {
+    animate,
+    byMouse,
+    skipPermitUnload,
+  } = {}) {
     // Telemetry stopwatches may already be running if removeTab gets
     // called again for an already closing tab.
     if (!TelemetryStopwatch.running("FX_TAB_CLOSE_TIME_ANIM_MS", aTab) &&
         !TelemetryStopwatch.running("FX_TAB_CLOSE_TIME_NO_ANIM_MS", aTab)) {
       // Speculatevely start both stopwatches now. We'll cancel one of
       // the two later depending on whether we're animating.
       TelemetryStopwatch.start("FX_TAB_CLOSE_TIME_ANIM_MS", aTab);
       TelemetryStopwatch.start("FX_TAB_CLOSE_TIME_NO_ANIM_MS", aTab);

--- a/browser/base/content/test/general/browser_ctrlTab.js
+++ b/browser/base/content/test/general/browser_ctrlTab.js
@@ -1,10 +1,10 @@
 add_task(async function() {
-  Services.prefs.setBoolPref("browser.ctrlTab.previews", true);
+  await SpecialPowers.pushPrefEnv({"set": [["browser.ctrlTab.recentlyUsedOrder", true]]});
 
   BrowserTestUtils.addTab(gBrowser);
   BrowserTestUtils.addTab(gBrowser);
   BrowserTestUtils.addTab(gBrowser);
 
   // While doing this test, we should make sure the selected tab in the tab
   // preview is not changed by mouse events.  That may happen after closing
   // the selected tab with ctrl+W.  Disable all mouse events to prevent it.
@@ -108,20 +108,16 @@ add_task(async function() {
     document.addEventListener("keypress", detectKeyEvent);
     await pressCtrlTab();
     document.removeEventListener("keypress", detectKeyEvent);
     ok(eventConsumed, "Ctrl+Tab consumed by the tabbed browser if one tab is open");
     is(focusedWindow, document.commandDispatcher.focusedWindow,
        "Ctrl+Tab doesn't change focus if one tab is open");
   }
 
-  // cleanup
-  if (Services.prefs.prefHasUserValue("browser.ctrlTab.previews"))
-    Services.prefs.clearUserPref("browser.ctrlTab.previews");
-
   /* private utility functions */
 
   function pressCtrlTab(aShiftKey) {
     let promise;
     if (!isOpen() && canOpen()) {
       promise = BrowserTestUtils.waitForEvent(ctrlTab.panel, "popupshown");
     } else {
       promise = BrowserTestUtils.waitForEvent(document, "keyup");
@@ -147,17 +143,18 @@ add_task(async function() {
     return promise;
   }
 
   function isOpen() {
     return ctrlTab.isOpen;
   }
 
   function canOpen() {
-    return Services.prefs.getBoolPref("browser.ctrlTab.previews") && gBrowser.tabs.length > 2;
+    return Services.prefs.getBoolPref("browser.ctrlTab.recentlyUsedOrder") &&
+           gBrowser.tabs.length > 2;
   }
 
   function checkTabs(aTabs) {
     is(gBrowser.tabs.length, aTabs, "number of open tabs should be " + aTabs);
   }
 
   function selectTabs(tabs) {
     tabs.forEach(function(index) {

--- a/browser/base/content/test/general/browser_tabkeynavigation.js
+++ b/browser/base/content/test/general/browser_tabkeynavigation.js
@@ -7,18 +7,20 @@ add_task(async function test() {
   let testPage2 = "data:text/html,<html id='tab2'><body><button id='button2'>Tab 2</button><script>function preventDefault(event) { event.preventDefault(); event.stopImmediatePropagation(); } window.addEventListener('keydown', preventDefault, true); window.addEventListener('keypress', preventDefault, true);</script></body></html>";
   let testPage3 = "data:text/html,<html id='tab3'><body><button id='button3'>Tab 3</button></body></html>";
 
   let tab1 = await BrowserTestUtils.openNewForegroundTab(gBrowser, testPage1);
   let browser1 = gBrowser.getBrowserForTab(tab1);
   let tab2 = await BrowserTestUtils.openNewForegroundTab(gBrowser, testPage2);
   let tab3 = await BrowserTestUtils.openNewForegroundTab(gBrowser, testPage3);
 
-  // Kill the animation for simpler test.
-  Services.prefs.setBoolPref("toolkit.cosmeticAnimations.enabled", false);
+  await SpecialPowers.pushPrefEnv({"set": [
+    ["toolkit.cosmeticAnimations.enabled", false],
+    ["browser.ctrlTab.recentlyUsedOrder", false],
+  ]});
 
   gBrowser.selectedTab = tab1;
   browser1.focus();
 
   is(gBrowser.selectedTab, tab1,
      "Tab1 should be activated");
   EventUtils.synthesizeKey("VK_TAB", { ctrlKey: true });
   is(gBrowser.selectedTab, tab2,
@@ -146,11 +148,9 @@ add_task(async function test() {
       is(gBrowser.tabs.length, 3,
         "The count of tabs should be 3 since renaming key events shouldn't close other tabs");
   }
 
   gBrowser.selectedTab = tab3;
   while (gBrowser.tabs.length > 1) {
     gBrowser.removeCurrentTab();
   }
-
-    Services.prefs.clearUserPref("toolkit.cosmeticAnimations.enabled");
 });

--- a/browser/base/content/test/general/browser_visibleTabs_tabPreview.js
+++ b/browser/base/content/test/general/browser_visibleTabs_tabPreview.js
@@ -1,14 +1,14 @@
 /* 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/. */
 
 add_task(async function test() {
-  Services.prefs.setBoolPref("browser.ctrlTab.previews", true);
+  await SpecialPowers.pushPrefEnv({"set": [["browser.ctrlTab.recentlyUsedOrder", true]]});
 
   let [origTab] = gBrowser.visibleTabs;
   let tabOne = BrowserTestUtils.addTab(gBrowser);
   let tabTwo = BrowserTestUtils.addTab(gBrowser);
 
   // test the ctrlTab.tabList
   pressCtrlTab();
   ok(ctrlTab.tabList.length, 3, "Show 3 tabs in tab preview");
@@ -22,19 +22,16 @@ add_task(async function test() {
   gBrowser.showOnlyTheseTabs([origTab, tabOne, tabTwo]);
   pressCtrlTab();
   ok(ctrlTab.isOpen, "With 3 tabs open, Ctrl+Tab does open the preview panel");
   releaseCtrl();
 
   // cleanup
   gBrowser.removeTab(tabOne);
   gBrowser.removeTab(tabTwo);
-
-  if (Services.prefs.prefHasUserValue("browser.ctrlTab.previews"))
-    Services.prefs.clearUserPref("browser.ctrlTab.previews");
 });
 
 function pressCtrlTab(aShiftKey) {
   EventUtils.synthesizeKey("VK_TAB", { ctrlKey: true, shiftKey: !!aShiftKey });
 }
 
 function releaseCtrl() {
   EventUtils.synthesizeKey("VK_CONTROL", { type: "keyup" });

--- a/browser/base/content/test/performance/browser_urlbar_keyed_search.js
+++ b/browser/base/content/test/performance/browser_urlbar_keyed_search.js
@@ -27,32 +27,16 @@ const EXPECTED_REFLOWS_FIRST_OPEN = [
       "openAutocompletePopup@chrome://browser/content/urlbarBindings.xml",
       "openPopup@chrome://global/content/bindings/autocomplete.xml",
       "set_popupOpen@chrome://global/content/bindings/autocomplete.xml"
     ],
   },
 
   {
     stack: [
-      "adjustHeight@chrome://global/content/bindings/autocomplete.xml",
-      "onxblpopupshown@chrome://global/content/bindings/autocomplete.xml"
-    ],
-    maxCount: 5, // This number should only ever go down - never up.
-  },
-
-  {
-    stack: [
-      "adjustHeight@chrome://global/content/bindings/autocomplete.xml",
-      "_invalidate/this._adjustHeightTimeout<@chrome://global/content/bindings/autocomplete.xml",
-    ],
-    maxCount: 51, // This number should only ever go down - never up.
-  },
-
-  {
-    stack: [
       "_handleOverflow@chrome://global/content/bindings/autocomplete.xml",
       "handleOverUnderflow@chrome://global/content/bindings/autocomplete.xml",
       "_reuseAcItem@chrome://global/content/bindings/autocomplete.xml",
       "_appendCurrentResult@chrome://global/content/bindings/autocomplete.xml",
       "_invalidate@chrome://global/content/bindings/autocomplete.xml",
       "invalidate@chrome://global/content/bindings/autocomplete.xml"
     ],
     maxCount: 60, // This number should only ever go down - never up.

--- a/browser/base/content/test/performance/browser_urlbar_search.js
+++ b/browser/base/content/test/performance/browser_urlbar_search.js
@@ -27,32 +27,16 @@ const EXPECTED_REFLOWS_FIRST_OPEN = [
       "openAutocompletePopup@chrome://browser/content/urlbarBindings.xml",
       "openPopup@chrome://global/content/bindings/autocomplete.xml",
       "set_popupOpen@chrome://global/content/bindings/autocomplete.xml"
     ],
   },
 
   {
     stack: [
-      "adjustHeight@chrome://global/content/bindings/autocomplete.xml",
-      "onxblpopupshown@chrome://global/content/bindings/autocomplete.xml"
-    ],
-    maxCount: 5, // This number should only ever go down - never up.
-  },
-
-  {
-    stack: [
-      "adjustHeight@chrome://global/content/bindings/autocomplete.xml",
-      "_invalidate/this._adjustHeightTimeout<@chrome://global/content/bindings/autocomplete.xml",
-    ],
-    maxCount: 6, // This number should only ever go down - never up.
-  },
-
-  {
-    stack: [
       "_handleOverflow@chrome://global/content/bindings/autocomplete.xml",
       "handleOverUnderflow@chrome://global/content/bindings/autocomplete.xml",
       "_reuseAcItem@chrome://global/content/bindings/autocomplete.xml",
       "_appendCurrentResult@chrome://global/content/bindings/autocomplete.xml",
       "_invalidate@chrome://global/content/bindings/autocomplete.xml",
       "invalidate@chrome://global/content/bindings/autocomplete.xml"
     ],
     maxCount: 36, // This number should only ever go down - never up.
@@ -80,32 +64,16 @@ const EXPECTED_REFLOWS_FIRST_OPEN = [
     ],
   },
 ];
 
 /* These reflows happen everytime the awesomebar panel opens. */
 const EXPECTED_REFLOWS_SECOND_OPEN = [
   {
     stack: [
-      "adjustHeight@chrome://global/content/bindings/autocomplete.xml",
-      "onxblpopupshown@chrome://global/content/bindings/autocomplete.xml"
-    ],
-    maxCount: 3, // This number should only ever go down - never up.
-  },
-
-  {
-    stack: [
-      "adjustHeight@chrome://global/content/bindings/autocomplete.xml",
-      "_invalidate/this._adjustHeightTimeout<@chrome://global/content/bindings/autocomplete.xml",
-    ],
-    maxCount: 6, // This number should only ever go down - never up.
-  },
-
-  {
-    stack: [
       "_handleOverflow@chrome://global/content/bindings/autocomplete.xml",
       "handleOverUnderflow@chrome://global/content/bindings/autocomplete.xml",
       "_reuseAcItem@chrome://global/content/bindings/autocomplete.xml",
       "_appendCurrentResult@chrome://global/content/bindings/autocomplete.xml",
       "_invalidate@chrome://global/content/bindings/autocomplete.xml",
       "invalidate@chrome://global/content/bindings/autocomplete.xml"
     ],
     maxCount: 24, // This number should only ever go down - never up.

--- a/browser/base/content/urlbarBindings.xml
+++ b/browser/base/content/urlbarBindings.xml
@@ -1906,16 +1906,20 @@ file, You can obtain one at http://mozil
           this, "anonid", "search-suggestions-notification"
         );
       </field>
 
       <field name="footer" readonly="true">
         document.getAnonymousElementByAttribute(this, "anonid", "footer");
       </field>
 
+      <field name="shrinkDelay" readonly="true">
+        250
+      </field>
+
       <field name="oneOffSearchButtons" readonly="true">
         document.getAnonymousElementByAttribute(this, "anonid",
                                                 "one-off-search-buttons");
       </field>
 
       <field name="_oneOffSearchesEnabled">false</field>
 
       <field name="_overrideValue">null</field>
@@ -2190,16 +2194,93 @@ file, You can obtain one at http://mozil
           if (needsHandleOverUnderflow) {
             for (let item of this.richlistbox.childNodes) {
               item.handleOverUnderflow();
             }
           }
         ]]></body>
       </method>
 
+      <method name="adjustHeight">
+        <body>
+          <![CDATA[
+          // If we were going to shrink later, cancel that for now:
+          if (this._shrinkTimeout) {
+            clearTimeout(this._shrinkTimeout);
+            this._shrinkTimeout = null;
+          }
+          let lastRowCount = this._lastRowCount;
+          // Figure out how many rows to show
+          let rows = this.richlistbox.childNodes;
+          this._lastRowCount = rows.length;
+          let numRows = Math.min(this.matchCount, this.maxRows, rows.length);
+
+          // If we're going from 0 to non-0 rows, we might need to remove
+          // the height attribute to allow the popup to size. The attribute
+          // is set from XUL popup management code.
+          if (!lastRowCount && rows.length) {
+            this.removeAttribute("height");
+          }
+
+          // Default the height to 0 if we have no rows to show
+          let height = 0;
+          if (numRows) {
+            if (!this._rowHeight) {
+              window.promiseDocumentFlushed(() => {
+                if (window.closed) {
+                  return;
+                }
+                this._rowHeight = rows[0].getBoundingClientRect().height;
+                let style = window.getComputedStyle(this.richlistbox);
+
+                let paddingTop = parseInt(style.paddingTop) || 0;
+                let paddingBottom = parseInt(style.paddingBottom) || 0;
+                this._rlbPadding = paddingTop + paddingBottom;
+                // Then re-run - but don't dirty layout from inside this callback.
+                window.requestAnimationFrame(() => this.adjustHeight());
+              });
+              return;
+            }
+
+            // Calculate the height to have the first row to last row shown
+            height = (this._rowHeight * numRows) + this._rlbPadding;
+          }
+
+          let animate = this.getAttribute("dontanimate") != "true";
+          let currentHeight =
+            parseFloat(this.richlistbox.getAttribute("height"), 10) ||
+            parseFloat(this.richlistbox.style.height, 10) ||
+            0; // It's possible we get here when we haven't set height on the richlistbox
+               // yet, which means parseFloat will return NaN. It should return 0 instead.
+          if (height > currentHeight) {
+            // Grow immediately.
+            if (animate) {
+              this.richlistbox.removeAttribute("height");
+              this.richlistbox.style.height = height + "px";
+            } else {
+              this.richlistbox.style.removeProperty("height");
+              this.richlistbox.height = height;
+            }
+          } else if (height < currentHeight) { // Don't shrink if height matches exactly
+            // Delay shrinking to avoid flicker.
+            this._shrinkTimeout = setTimeout(() => {
+              this._collapseUnusedItems();
+              if (animate) {
+                this.richlistbox.removeAttribute("height");
+                this.richlistbox.style.height = height + "px";
+              } else {
+                this.richlistbox.style.removeProperty("height");
+                this.richlistbox.height = height;
+              }
+            }, this.shrinkDelay);
+          }
+          ]]>
+        </body>
+      </method>
+
       <method name="_showSearchSuggestionsNotification">
         <parameter name="whichNotification"/>
         <parameter name="popupDirection"/>
         <body>
           <![CDATA[
           if (whichNotification == "opt-out") {
             if (this.margins) {
               this.searchSuggestionsNotification.style.paddingInlineStart =

--- a/browser/components/about/AboutPrivateBrowsingHandler.jsm
+++ b/browser/components/about/AboutPrivateBrowsingHandler.jsm
@@ -2,17 +2,16 @@
  * 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 EXPORTED_SYMBOLS = ["AboutPrivateBrowsingHandler"];
 
 ChromeUtils.import("resource://gre/modules/RemotePageManager.jsm");
-ChromeUtils.import("resource://gre/modules/Services.jsm");
 
 var AboutPrivateBrowsingHandler = {
   _topics: [
     "DontShowIntroPanelAgain",
     "OpenPrivateWindow",
   ],
 
   init() {

--- a/browser/components/customizableui/DragPositionManager.jsm
+++ b/browser/components/customizableui/DragPositionManager.jsm
@@ -1,17 +1,14 @@
 /* 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.import("resource:///modules/CustomizableUI.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
-
 var gManagers = new WeakMap();
 
 const kPaletteId = "customization-palette";
 
 var EXPORTED_SYMBOLS = ["DragPositionManager"];
 
 function AreaPositionManager(aContainer) {
   // Caching the direction and bounds of the container for quick access later:

--- a/browser/components/customizableui/ScrollbarSampler.jsm
+++ b/browser/components/customizableui/ScrollbarSampler.jsm
@@ -2,17 +2,16 @@
  * 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 EXPORTED_SYMBOLS = ["ScrollbarSampler"];
 
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 
 var gSystemScrollbarWidth = null;
 
 var ScrollbarSampler = {
   getSystemScrollbarWidth() {
     if (gSystemScrollbarWidth !== null) {
       return Promise.resolve(gSystemScrollbarWidth);
     }

--- a/browser/components/customizableui/SearchWidgetTracker.jsm
+++ b/browser/components/customizableui/SearchWidgetTracker.jsm
@@ -6,17 +6,16 @@
  * Keeps the "browser.search.widget.inNavBar" preference synchronized.
  */
 
 "use strict";
 
 var EXPORTED_SYMBOLS = ["SearchWidgetTracker"];
 
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 
 ChromeUtils.defineModuleGetter(this, "CustomizableUI",
                                "resource:///modules/CustomizableUI.jsm");
 
 const WIDGET_ID = "search-container";
 const PREF_NAME = "browser.search.widget.inNavBar";
 
 const SearchWidgetTracker = {

--- a/browser/components/extensions/ExtensionControlledPopup.jsm
+++ b/browser/components/extensions/ExtensionControlledPopup.jsm
@@ -15,17 +15,16 @@
  * changed the New Tab or homepage. Users would see this popup the first time they
  * view those pages after a change to the setting in each session until they confirm
  * the change by triggering the primary action.
  */
 
 var EXPORTED_SYMBOLS = ["ExtensionControlledPopup"];
 
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/ExtensionUtils.jsm");
 ChromeUtils.import("resource://gre/modules/ExtensionCommon.jsm");
 ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 
 ChromeUtils.defineModuleGetter(this, "AddonManager",
                                "resource://gre/modules/AddonManager.jsm");
 ChromeUtils.defineModuleGetter(this, "BrowserUtils",
                                "resource://gre/modules/BrowserUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "CustomizableUI",

--- a/browser/components/migration/360seProfileMigrator.js
+++ b/browser/components/migration/360seProfileMigrator.js
@@ -1,16 +1,15 @@
 /* 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.import("resource://gre/modules/XPCOMUtils.jsm");
-ChromeUtils.import("resource://gre/modules/Services.jsm");
 ChromeUtils.import("resource://gre/modules/NetUtil.jsm");
 ChromeUtils.import("resource://gre/modules/FileUtils.jsm");
 ChromeUtils.import("resource://gre/modules/osfile.jsm");
 ChromeUtils.import("resource:///modules/MigrationUtils.jsm");
 
 ChromeUtils.defineModuleGetter(this, "PlacesUtils",
                                "resource://gre/modules/PlacesUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "Sqlite",

--- a/browser/components/migration/ChromeMigrationUtils.jsm
+++ b/browser/components/migration/ChromeMigrationUtils.jsm
@@ -1,20 +1,18 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 "use strict";
 
 var EXPORTED_SYMBOLS = ["ChromeMigrationUtils"];
 
 ChromeUtils.import("resource://gre/modules/AppConstants.jsm");
-ChromeUtils.import("resource://gre/modules/NetUtil.jsm");
 ChromeUtils.import("resource://gre/modules/osfile.jsm");
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 
 var ChromeMigrationUtils = {
   _extensionVersionDirectoryNames: {},
 
   // The cache for the locale strings.
   // For example, the data could be:
   // {
   //   "profile-id-1": {

--- a/browser/components/migration/EdgeProfileMigrator.js
+++ b/browser/components/migration/EdgeProfileMigrator.js
@@ -1,17 +1,16 @@
 /* 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.import("resource://gre/modules/AppConstants.jsm");
 ChromeUtils.import("resource://gre/modules/osfile.jsm");
-ChromeUtils.import("resource://gre/modules/Services.jsm");
 ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource:///modules/MigrationUtils.jsm");
 ChromeUtils.import("resource:///modules/MSMigrationUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "PlacesUtils",
                                "resource://gre/modules/PlacesUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "ESEDBReader",
                                "resource:///modules/ESEDBReader.jsm");
 

--- a/browser/components/migration/SafariProfileMigrator.js
+++ b/browser/components/migration/SafariProfileMigrator.js
@@ -1,18 +1,16 @@
 /* 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.import("resource://gre/modules/AppConstants.jsm");
 ChromeUtils.import("resource://gre/modules/FileUtils.jsm");
 ChromeUtils.import("resource://gre/modules/osfile.jsm");
-ChromeUtils.import("resource://gre/modules/Services.jsm");
 ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource:///modules/MigrationUtils.jsm");
 
 ChromeUtils.defineModuleGetter(this, "PropertyListUtils",
                                "resource://gre/modules/PropertyListUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "PlacesUtils",
                                "resource://gre/modules/PlacesUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "FormHistory",

--- a/browser/components/migration/tests/unit/test_IE7_passwords.js
+++ b/browser/components/migration/tests/unit/test_IE7_passwords.js
@@ -1,12 +1,11 @@
 "use strict";
 
 ChromeUtils.import("resource://gre/modules/AppConstants.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 
 ChromeUtils.defineModuleGetter(this, "OSCrypto",
                                "resource://gre/modules/OSCrypto.jsm");
 
 const IE7_FORM_PASSWORDS_MIGRATOR_NAME = "IE7FormPasswords";
 const LOGINS_KEY = "Software\\Microsoft\\Internet Explorer\\IntelliForms\\Storage2";
 const EXTENSION = "-backup";
 const TESTED_WEBSITES = {

--- a/browser/components/nsBrowserGlue.js
+++ b/browser/components/nsBrowserGlue.js
@@ -1808,17 +1808,17 @@ BrowserGlue.prototype = {
       }
     }
   },
 
   // eslint-disable-next-line complexity
   _migrateUI: function BG__migrateUI() {
     // Use an increasing number to keep track of the current migration state.
     // Completely unrelated to the current Firefox release number.
-    const UI_VERSION = 69;
+    const UI_VERSION = 70;
     const BROWSER_DOCURL = AppConstants.BROWSER_CHROME_URL;
 
     let currentUIVersion;
     if (Services.prefs.prefHasUserValue("browser.migration.version")) {
       currentUIVersion = Services.prefs.getIntPref("browser.migration.version");
     } else {
       // This is a new profile, nothing to migrate.
       Services.prefs.setIntPref("browser.migration.version", UI_VERSION);
@@ -2120,16 +2120,27 @@ BrowserGlue.prototype = {
       if (socialPrefs) {
         let socialPrefsArray = socialPrefs.getChildList("");
         for (let item of socialPrefsArray) {
           Services.prefs.clearUserPref("social." + item);
         }
       }
     }
 
+    if (currentUIVersion < 70) {
+      // Migrate old ctrl-tab pref to new one in existing profiles. (This code
+      // doesn't run at all in new profiles.)
+      Services.prefs.setBoolPref("browser.ctrlTab.recentlyUsedOrder",
+        Services.prefs.getBoolPref("browser.ctrlTab.previews", false));
+      Services.prefs.clearUserPref("browser.ctrlTab.previews");
+      // Remember that we migrated the pref in case we decide to flip it for
+      // these users.
+      Services.prefs.setBoolPref("browser.ctrlTab.migrated", true);
+    }
+
     // Update the migration version.
     Services.prefs.setIntPref("browser.migration.version", UI_VERSION);
   },
 
   _checkForDefaultBrowser() {
     // Perform default browser checking.
     if (!ShellService) {
       return;

--- a/browser/components/preferences/in-content/main.js
+++ b/browser/components/preferences/in-content/main.js
@@ -138,17 +138,17 @@ Preferences.addAll([
   - true if tabs are to be shown in the Windows 7 taskbar
   */
 
   { id: "browser.link.open_newwindow", type: "int" },
   { id: "browser.tabs.loadInBackground", type: "bool", inverted: true },
   { id: "browser.tabs.warnOnClose", type: "bool" },
   { id: "browser.tabs.warnOnOpen", type: "bool" },
   { id: "browser.sessionstore.restore_on_demand", type: "bool" },
-  { id: "browser.ctrlTab.previews", type: "bool" },
+  { id: "browser.ctrlTab.recentlyUsedOrder", type: "bool" },
 
   // Fonts
   { id: "font.language.group", type: "wstring" },
 
   // Languages
   { id: "browser.translation.detectLanguage", type: "bool" },
 
   // General tab

--- a/browser/components/preferences/in-content/main.xul
+++ b/browser/components/preferences/in-content/main.xul
@@ -72,17 +72,18 @@
 </groupbox>
 
 <!-- Tab preferences -->
 <groupbox data-category="paneGeneral"
           hidden="true">
     <caption><label data-l10n-id="tabs-group-header"/></caption>
 
     <checkbox id="ctrlTabRecentlyUsedOrder" data-l10n-id="ctrl-tab-recently-used-order"
-              preference="browser.ctrlTab.previews"/>
+              preference="browser.ctrlTab.recentlyUsedOrder"
+              oncommand="Services.prefs.clearUserPref('browser.ctrlTab.migrated');"/>
 
     <checkbox id="linkTargeting" data-l10n-id="open-new-link-as-tabs"
               preference="browser.link.open_newwindow"
               onsyncfrompreference="return gMainPane.readLinkTarget();"
               onsynctopreference="return gMainPane.writeLinkTarget();"/>
 
     <checkbox id="warnCloseMultiple" data-l10n-id="warn-on-close-multiple-tabs"
               preference="browser.tabs.warnOnClose"/>

--- a/browser/components/preferences/in-content/privacy.xul
+++ b/browser/components/preferences/in-content/privacy.xul
@@ -348,18 +348,18 @@
         </hbox>
       </vbox>
     </hbox>
     <vbox id="doNotTrackLearnMoreBox">
       <label><label class="tail-with-learn-more" data-l10n-id="do-not-track-description"></label><label
       class="learnMore text-link" href="https://www.mozilla.org/dnt"
       data-l10n-id="do-not-track-learn-more"></label></label>
       <radiogroup id="doNotTrackRadioGroup" aria-labelledby="doNotTrackDesc" preference="privacy.donottrackheader.enabled">
+        <radio value="true" data-l10n-id="do-not-track-option-always"/>
         <radio value="false" data-l10n-id="do-not-track-option-default"/>
-        <radio value="true" data-l10n-id="do-not-track-option-always"/>
       </radiogroup>
     </vbox>
   </vbox>
 </groupbox>
 
 <hbox id="permissionsCategory"
       class="subcategory"
       hidden="true"

--- a/browser/components/sessionstore/ContentRestore.jsm
+++ b/browser/components/sessionstore/ContentRestore.jsm
@@ -1,17 +1,16 @@
 /* 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 EXPORTED_SYMBOLS = ["ContentRestore"];
 
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm", this);
 ChromeUtils.import("resource://gre/modules/Services.jsm", this);
 
 ChromeUtils.defineModuleGetter(this, "DocShellCapabilities",
   "resource:///modules/sessionstore/DocShellCapabilities.jsm");
 ChromeUtils.defineModuleGetter(this, "FormData",
   "resource://gre/modules/FormData.jsm");
 ChromeUtils.defineModuleGetter(this, "ScrollPosition",
   "resource://gre/modules/ScrollPosition.jsm");

--- a/browser/components/sessionstore/RecentlyClosedTabsAndWindowsMenuUtils.jsm
+++ b/browser/components/sessionstore/RecentlyClosedTabsAndWindowsMenuUtils.jsm
@@ -1,19 +1,17 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 var EXPORTED_SYMBOLS = ["RecentlyClosedTabsAndWindowsMenuUtils"];
 
 const kNSXUL = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
 
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/PlacesUtils.jsm");
 
 ChromeUtils.defineModuleGetter(this, "PluralForm",
                                "resource://gre/modules/PluralForm.jsm");
 ChromeUtils.defineModuleGetter(this, "SessionStore",
                                "resource:///modules/sessionstore/SessionStore.jsm");
 
 var navigatorBundle = Services.strings.createBundle("chrome://browser/locale/browser.properties");
 

--- a/browser/components/sessionstore/SessionCookies.jsm
+++ b/browser/components/sessionstore/SessionCookies.jsm
@@ -2,17 +2,16 @@
  * 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 EXPORTED_SYMBOLS = ["SessionCookies"];
 
 ChromeUtils.import("resource://gre/modules/Services.jsm", this);
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm", this);
 
 ChromeUtils.defineModuleGetter(this, "PrivacyLevel",
   "resource://gre/modules/sessionstore/PrivacyLevel.jsm");
 
 const MAX_EXPIRY = Number.MAX_SAFE_INTEGER;
 
 /**
  * The external API implemented by the SessionCookies module.

--- a/browser/components/sessionstore/SessionStorage.jsm
+++ b/browser/components/sessionstore/SessionStorage.jsm
@@ -2,17 +2,16 @@
 * 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 EXPORTED_SYMBOLS = ["SessionStorage"];
 
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 
 const ssu = Cc["@mozilla.org/browser/sessionstore/utils;1"]
               .createInstance(Ci.nsISessionStoreUtils);
 
 // A bound to the size of data to store for DOM Storage.
 const DOM_STORAGE_LIMIT_PREF = "browser.sessionstore.dom_storage_limit";
 
 // Returns the principal for a given |frame| contained in a given |docShell|.

--- a/browser/components/sessionstore/StartupPerformance.jsm
+++ b/browser/components/sessionstore/StartupPerformance.jsm
@@ -1,18 +1,16 @@
 /* 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 EXPORTED_SYMBOLS = ["StartupPerformance"];
 
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm", this);
-
 ChromeUtils.defineModuleGetter(this, "Services",
   "resource://gre/modules/Services.jsm");
 ChromeUtils.defineModuleGetter(this, "setTimeout",
   "resource://gre/modules/Timer.jsm");
 ChromeUtils.defineModuleGetter(this, "clearTimeout",
   "resource://gre/modules/Timer.jsm");
 
 const COLLECT_RESULTS_AFTER_MS = 10000;

--- a/browser/components/sessionstore/TabState.jsm
+++ b/browser/components/sessionstore/TabState.jsm
@@ -1,18 +1,16 @@
 /* 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 EXPORTED_SYMBOLS = ["TabState"];
 
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm", this);
-
 ChromeUtils.defineModuleGetter(this, "PrivacyFilter",
   "resource://gre/modules/sessionstore/PrivacyFilter.jsm");
 ChromeUtils.defineModuleGetter(this, "TabStateCache",
   "resource:///modules/sessionstore/TabStateCache.jsm");
 ChromeUtils.defineModuleGetter(this, "TabAttributes",
   "resource:///modules/sessionstore/TabAttributes.jsm");
 ChromeUtils.defineModuleGetter(this, "Utils",
   "resource://gre/modules/sessionstore/Utils.jsm");

--- a/browser/components/shell/HeadlessShell.jsm
+++ b/browser/components/shell/HeadlessShell.jsm
@@ -2,17 +2,16 @@
  * 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 EXPORTED_SYMBOLS = ["HeadlessShell"];
 
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://gre/modules/osfile.jsm");
 
 // Refrences to the progress listeners to keep them from being gc'ed
 // before they are called.
 const progressListeners = new Map();
 
 function loadContentWindow(webNavigation, uri) {
   return new Promise((resolve, reject) => {

--- a/browser/components/translation/BingTranslator.jsm
+++ b/browser/components/translation/BingTranslator.jsm
@@ -2,17 +2,16 @@
  * 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 EXPORTED_SYMBOLS = [ "BingTranslator" ];
 
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/Log.jsm");
 ChromeUtils.import("resource://gre/modules/PromiseUtils.jsm");
 ChromeUtils.import("resource://services-common/async.js");
 ChromeUtils.import("resource://gre/modules/Http.jsm");
 ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 
 XPCOMUtils.defineLazyGlobalGetters(this, ["XMLHttpRequest"]);
 
 // The maximum amount of net data allowed per request on Bing's API.

--- a/browser/components/translation/LanguageDetector.jsm
+++ b/browser/components/translation/LanguageDetector.jsm
@@ -2,17 +2,16 @@
  * 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 EXPORTED_SYMBOLS = ["LanguageDetector"];
 
 ChromeUtils.import("resource://gre/modules/Timer.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 
 // Since Emscripten can handle heap growth, but not heap shrinkage, we
 // need to refresh the worker after we've processed a particularly large
 // string in order to prevent unnecessary resident memory growth.
 //
 // These values define the cut-off string length and the idle timeout
 // (in milliseconds) before destroying a worker. Once a string of the
 // maximum size has been processed, the worker is marked for

--- a/browser/components/translation/TranslationContentHandler.jsm
+++ b/browser/components/translation/TranslationContentHandler.jsm
@@ -2,17 +2,16 @@
  * 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 EXPORTED_SYMBOLS = [ "TranslationContentHandler" ];
 
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "LanguageDetector",
   "resource:///modules/translation/LanguageDetector.jsm");
 
 const STATE_OFFER = 0;
 const STATE_TRANSLATED = 2;
 const STATE_ERROR = 3;
 
 var TranslationContentHandler = function(global, docShell) {

--- a/browser/components/translation/YandexTranslator.jsm
+++ b/browser/components/translation/YandexTranslator.jsm
@@ -2,17 +2,16 @@
  * 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 EXPORTED_SYMBOLS = [ "YandexTranslator" ];
 
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/Log.jsm");
 ChromeUtils.import("resource://gre/modules/PromiseUtils.jsm");
 ChromeUtils.import("resource://services-common/async.js");
 ChromeUtils.import("resource://gre/modules/Http.jsm");
 ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 
 XPCOMUtils.defineLazyGlobalGetters(this, ["XMLHttpRequest"]);
 
 // The maximum amount of net data allowed per request on Bing's API.

--- a/browser/extensions/formautofill/FormAutofillDoorhanger.jsm
+++ b/browser/extensions/formautofill/FormAutofillDoorhanger.jsm
@@ -2,25 +2,22 @@
  * 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/. */
 
 /*
  * Implements doorhanger singleton that wraps up the PopupNotifications and handles
  * the doorhager UI for formautofill related features.
  */
 
-/* exported FormAutofillDoorhanger */
-
 "use strict";
 
 var EXPORTED_SYMBOLS = ["FormAutofillDoorhanger"];
 
 ChromeUtils.import("resource://gre/modules/AppConstants.jsm");
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://formautofill/FormAutofill.jsm");
 ChromeUtils.import("resource://formautofill/FormAutofillUtils.jsm");
 
 this.log = null;
 FormAutofill.defineLazyLogGetter(this, EXPORTED_SYMBOLS[0]);
 
 const GetStringFromName = FormAutofillUtils.stringBundle.GetStringFromName;
 const formatStringFromName = FormAutofillUtils.stringBundle.formatStringFromName;

--- a/browser/extensions/formautofill/FormAutofillHandler.jsm
+++ b/browser/extensions/formautofill/FormAutofillHandler.jsm
@@ -1,24 +1,21 @@
 /* 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/. */
 
 /*
  * Defines a handler object to represent forms that autofill can handle.
  */
 
-/* exported FormAutofillHandler */
-
 "use strict";
 
 var EXPORTED_SYMBOLS = ["FormAutofillHandler"];
 
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 
 ChromeUtils.import("resource://formautofill/FormAutofill.jsm");
 
 ChromeUtils.defineModuleGetter(this, "FormAutofillUtils",
                                "resource://formautofill/FormAutofillUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "FormAutofillHeuristics",
                                "resource://formautofill/FormAutofillHeuristics.jsm");
 ChromeUtils.defineModuleGetter(this, "FormLikeFactory",

--- a/browser/extensions/formautofill/FormAutofillPreferences.jsm
+++ b/browser/extensions/formautofill/FormAutofillPreferences.jsm
@@ -13,17 +13,16 @@ var EXPORTED_SYMBOLS = ["FormAutofillPre
 // Add addresses enabled flag in telemetry environment for recording the number of
 // users who disable/enable the address autofill feature.
 const BUNDLE_URI = "chrome://formautofill/locale/formautofill.properties";
 const MANAGE_ADDRESSES_URL = "chrome://formautofill/content/manageAddresses.xhtml";
 const MANAGE_CREDITCARDS_URL = "chrome://formautofill/content/manageCreditCards.xhtml";
 const XUL_NS = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
 
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://formautofill/FormAutofill.jsm");
 ChromeUtils.import("resource://formautofill/FormAutofillUtils.jsm");
 
 const {
   ENABLED_AUTOFILL_ADDRESSES_PREF,
   ENABLED_AUTOFILL_CREDITCARDS_PREF,
   MANAGE_ADDRESSES_KEYWORDS,
   EDIT_ADDRESS_KEYWORDS,

--- a/browser/extensions/formautofill/FormAutofillSync.jsm
+++ b/browser/extensions/formautofill/FormAutofillSync.jsm
@@ -2,17 +2,16 @@
  * 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 EXPORTED_SYMBOLS = ["AddressesEngine", "CreditCardsEngine"];
 
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://services-sync/engines.js");
 ChromeUtils.import("resource://services-sync/record.js");
 ChromeUtils.import("resource://services-sync/util.js");
 ChromeUtils.import("resource://services-sync/constants.js");
 ChromeUtils.import("resource://formautofill/FormAutofillUtils.jsm");
 
 ChromeUtils.defineModuleGetter(this, "Log",
                                "resource://gre/modules/Log.jsm");

--- a/browser/extensions/formautofill/ProfileAutoCompleteResult.jsm
+++ b/browser/extensions/formautofill/ProfileAutoCompleteResult.jsm
@@ -1,19 +1,16 @@
 /* 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/. */
 
-/* exported AddressResult, CreditCardResult */
-
 "use strict";
 
 var EXPORTED_SYMBOLS = ["AddressResult", "CreditCardResult"];
 
-ChromeUtils.import("resource://gre/modules/Services.jsm");
 ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://formautofill/FormAutofill.jsm");
 ChromeUtils.defineModuleGetter(this, "FormAutofillUtils",
                                "resource://formautofill/FormAutofillUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "CreditCard",
   "resource://gre/modules/CreditCard.jsm");
 
 XPCOMUtils.defineLazyPreferenceGetter(this, "insecureWarningEnabled", "security.insecure_field_warning.contextual.enabled");

--- a/browser/extensions/formautofill/bootstrap.js
+++ b/browser/extensions/formautofill/bootstrap.js
@@ -121,16 +121,17 @@ function startup(data) {
   } else {
     Services.prefs.clearUserPref("services.sync.engine.creditcards.available");
   }
 
   // Listen for the autocomplete popup message to lazily append our stylesheet related to the popup.
   Services.mm.addMessageListener("FormAutoComplete:MaybeOpenPopup", onMaybeOpenPopup);
 
   formAutofillParent.init().catch(Cu.reportError);
+  /* exported FormAutofillContent */
   Services.ppmm.loadProcessScript("data:,new " + function() {
     ChromeUtils.import("resource://formautofill/FormAutofillContent.jsm");
   }, true);
   Services.mm.loadFrameScript("chrome://formautofill/content/FormAutofillFrameScript.js", true);
 }
 
 function shutdown() {
   resProto.setSubstitution(RESOURCE_HOST, null);

--- a/browser/extensions/formautofill/phonenumberutils/PhoneNumber.jsm
+++ b/browser/extensions/formautofill/phonenumberutils/PhoneNumber.jsm
@@ -4,17 +4,16 @@
 
 // This library came from https://github.com/andreasgal/PhoneNumber.js but will
 // be further maintained by our own in Form Autofill codebase.
 
 "use strict";
 
 var EXPORTED_SYMBOLS = ["PhoneNumber"];
 
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "PHONE_NUMBER_META_DATA",
                                "resource://formautofill/phonenumberutils/PhoneNumberMetaData.jsm");
 ChromeUtils.defineModuleGetter(this, "PhoneNumberNormalizer",
                                "resource://formautofill/phonenumberutils/PhoneNumberNormalizer.jsm");
 var PhoneNumber = (function(dataBase) {
   const MAX_PHONE_NUMBER_LENGTH = 50;
   const NON_ALPHA_CHARS = /[^a-zA-Z]/g;
   const NON_DIALABLE_CHARS = /[^,#+\*\d]/g;

--- a/browser/extensions/formautofill/test/unit/test_activeStatus.js
+++ b/browser/extensions/formautofill/test/unit/test_activeStatus.js
@@ -1,16 +1,15 @@
 /*
  * Test for status handling in Form Autofill Parent.
  */
 
 "use strict";
 
 let {FormAutofillParent} = ChromeUtils.import("resource://formautofill/FormAutofillParent.jsm", {});
-ChromeUtils.import("resource://formautofill/FormAutofillStorage.jsm");
 
 add_task(async function test_activeStatus_init() {
   let formAutofillParent = new FormAutofillParent();
   sinon.spy(formAutofillParent, "_updateStatus");
 
   // Default status is null before initialization
   Assert.equal(formAutofillParent._active, null);
   Assert.equal(Services.ppmm.initialProcessData.autofillEnabled, undefined);

--- a/browser/extensions/formautofill/test/unit/test_getRecords.js
+++ b/browser/extensions/formautofill/test/unit/test_getRecords.js
@@ -1,17 +1,16 @@
 /*
  * Test for make sure getRecords can retrieve right collection from storage.
  */
 
 "use strict";
 
 let {FormAutofillParent} = ChromeUtils.import("resource://formautofill/FormAutofillParent.jsm", {});
 ChromeUtils.import("resource://formautofill/MasterPassword.jsm");
-ChromeUtils.import("resource://formautofill/FormAutofillStorage.jsm");
 ChromeUtils.import("resource://gre/modules/CreditCard.jsm");
 
 const TEST_ADDRESS_1 = {
   "given-name": "Timothy",
   "additional-name": "John",
   "family-name": "Berners-Lee",
   organization: "World Wide Web Consortium",
   "street-address": "32 Vassar Street\nMIT Room 32-G524",

--- a/browser/extensions/formautofill/test/unit/test_savedFieldNames.js
+++ b/browser/extensions/formautofill/test/unit/test_savedFieldNames.js
@@ -1,16 +1,15 @@
 /*
  * Test for keeping the valid fields information in initialProcessData.
  */
 
 "use strict";
 
 let {FormAutofillParent} = ChromeUtils.import("resource://formautofill/FormAutofillParent.jsm", {});
-ChromeUtils.import("resource://formautofill/FormAutofillStorage.jsm");
 
 add_task(async function test_profileSavedFieldNames_init() {
   let formAutofillParent = new FormAutofillParent();
   sinon.stub(formAutofillParent, "_updateSavedFieldNames");
 
   await formAutofillParent.init();
   await formAutofillParent.formAutofillStorage.initialize();
   Assert.equal(formAutofillParent._updateSavedFieldNames.called, true);

--- a/browser/extensions/onboarding/OnboardingTourType.jsm
+++ b/browser/extensions/onboarding/OnboardingTourType.jsm
@@ -1,18 +1,16 @@
 /* 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 EXPORTED_SYMBOLS = ["OnboardingTourType"];
 
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
-
 ChromeUtils.defineModuleGetter(this, "Services",
   "resource://gre/modules/Services.jsm");
 
 var OnboardingTourType = {
   /**
    * Determine the current tour type (new user tour or update user tour).
    * The function checks 2 criterias
    *  - TOURSET_VERSION: current onboarding tourset version

--- a/browser/extensions/pocket/content/Pocket.jsm
+++ b/browser/extensions/pocket/content/Pocket.jsm
@@ -1,17 +1,16 @@
   /* 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 EXPORTED_SYMBOLS = ["Pocket"];
 
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://gre/modules/Services.jsm");
 
 ChromeUtils.defineModuleGetter(this, "BrowserUtils",
   "resource://gre/modules/BrowserUtils.jsm");
 
 var Pocket = {
   get site() { return Services.prefs.getCharPref("extensions.pocket.site"); },
   get listURL() { return "https://" + Pocket.site + "/?src=ff_ext"; },

--- a/browser/modules/BlockedSiteContent.jsm
+++ b/browser/modules/BlockedSiteContent.jsm
@@ -1,14 +1,13 @@
 /* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
 /* 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/. */
 
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://gre/modules/Services.jsm");
 
 var EXPORTED_SYMBOLS = ["BlockedSiteContent"];
 
 ChromeUtils.defineModuleGetter(this, "SafeBrowsing",
                                "resource://gre/modules/SafeBrowsing.jsm");
 
 function getSiteBlockedErrorDetails(docShell) {

--- a/browser/modules/BrowserUsageTelemetry.jsm
+++ b/browser/modules/BrowserUsageTelemetry.jsm
@@ -8,17 +8,16 @@
 var EXPORTED_SYMBOLS = [
   "BrowserUsageTelemetry",
   "URLBAR_SELECTED_RESULT_TYPES",
   "URLBAR_SELECTED_RESULT_METHODS",
   "MINIMUM_TAB_COUNT_INTERVAL_MS",
  ];
 
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 
 ChromeUtils.defineModuleGetter(this, "PrivateBrowsingUtils",
                                "resource://gre/modules/PrivateBrowsingUtils.jsm");
 
 // The upper bound for the count of the visited unique domain names.
 const MAX_UNIQUE_VISITED_DOMAINS = 100;
 
 // Observed topic names.

--- a/browser/modules/ClickEventHandler.jsm
+++ b/browser/modules/ClickEventHandler.jsm
@@ -1,18 +1,15 @@
 /* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 var EXPORTED_SYMBOLS = ["ClickEventHandler"];
 
-/* eslint no-unused-vars: ["error", {args: "none"}] */
-
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://gre/modules/Services.jsm");
 
 ChromeUtils.defineModuleGetter(this, "BlockedSiteContent",
                                "resource:///modules/BlockedSiteContent.jsm");
 ChromeUtils.defineModuleGetter(this, "BrowserUtils",
                                "resource://gre/modules/BrowserUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "NetErrorContent",
                                "resource:///modules/NetErrorContent.jsm");

--- a/browser/modules/ContentClick.jsm
+++ b/browser/modules/ContentClick.jsm
@@ -3,17 +3,16 @@
  * 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 EXPORTED_SYMBOLS = [ "ContentClick" ];
 
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 
 ChromeUtils.defineModuleGetter(this, "PlacesUIUtils",
                                "resource:///modules/PlacesUIUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "PrivateBrowsingUtils",
                                "resource://gre/modules/PrivateBrowsingUtils.jsm");
 
 var ContentClick = {
   // Listeners are added in nsBrowserGlue.js

--- a/browser/modules/Feeds.jsm
+++ b/browser/modules/Feeds.jsm
@@ -1,17 +1,16 @@
 /* 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 EXPORTED_SYMBOLS = [ "Feeds" ];
 
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://gre/modules/Services.jsm");
 
 ChromeUtils.defineModuleGetter(this, "BrowserUtils",
                                "resource://gre/modules/BrowserUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "BrowserWindowTracker",
                                "resource:///modules/BrowserWindowTracker.jsm");
 
 var Feeds = {

--- a/browser/modules/FormSubmitObserver.jsm
+++ b/browser/modules/FormSubmitObserver.jsm
@@ -10,17 +10,16 @@
  * to get notifications about invalid forms. See HTMLFormElement
  * for details.
  */
 
 "use strict";
 
 var EXPORTED_SYMBOLS = [ "FormSubmitObserver" ];
 
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://gre/modules/Services.jsm");
 ChromeUtils.import("resource://gre/modules/BrowserUtils.jsm");
 
 function FormSubmitObserver(aWindow, aTabChildGlobal) {
   this.init(aWindow, aTabChildGlobal);
 }
 
 FormSubmitObserver.prototype =

--- a/browser/modules/FormValidationHandler.jsm
+++ b/browser/modules/FormValidationHandler.jsm
@@ -5,18 +5,16 @@
 /*
  * Chrome side handling of form validation popup.
  */
 
 "use strict";
 
 var EXPORTED_SYMBOLS = [ "FormValidationHandler" ];
 
-ChromeUtils.import("resource://gre/modules/Services.jsm");
-
 var FormValidationHandler =
 {
   _panel: null,
   _anchor: null,
 
   /*
    * Public apis
    */

--- a/browser/modules/PageActions.jsm
+++ b/browser/modules/PageActions.jsm
@@ -9,17 +9,16 @@ var EXPORTED_SYMBOLS = [
   // PageActions.Action
   // PageActions.ACTION_ID_BOOKMARK
   // PageActions.ACTION_ID_BOOKMARK_SEPARATOR
   // PageActions.ACTION_ID_BUILT_IN_SEPARATOR
   // PageActions.ACTION_ID_TRANSIENT_SEPARATOR
 ];
 
 ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 
 ChromeUtils.defineModuleGetter(this, "AppConstants",
   "resource://gre/modules/AppConstants.jsm");
 ChromeUtils.defineModuleGetter(this, "AsyncShutdown",
   "resource://gre/modules/AsyncShutdown.jsm");
 ChromeUtils.defineModuleGetter(this, "BinarySearch",
   "resource://gre/modules/BinarySearch.jsm");
 

--- a/browser/modules/PageStyleHandler.jsm
+++ b/browser/modules/PageStyleHandler.jsm
@@ -1,13 +1,12 @@
 /* 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/. */
 
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://gre/modules/Services.jsm");
 
 var EXPORTED_SYMBOLS = ["PageStyleHandler"];
 
 var PageStyleHandler = {
   getViewer(content) {
     return content.document.docShell.contentViewer;
   },

--- a/browser/modules/ReaderParent.jsm
+++ b/browser/modules/ReaderParent.jsm
@@ -2,17 +2,16 @@
 /* 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 EXPORTED_SYMBOLS = [ "ReaderParent" ];
 
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://gre/modules/Services.jsm");
 
 ChromeUtils.defineModuleGetter(this, "PlacesUtils", "resource://gre/modules/PlacesUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "ReaderMode", "resource://gre/modules/ReaderMode.jsm");
 
 const gStringBundle = Services.strings.createBundle("chrome://global/locale/aboutReader.properties");
 
 var ReaderParent = {

--- a/browser/modules/RemotePrompt.jsm
+++ b/browser/modules/RemotePrompt.jsm
@@ -2,18 +2,16 @@
 /* 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 EXPORTED_SYMBOLS = [ "RemotePrompt" ];
 
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
-
 ChromeUtils.defineModuleGetter(this, "PromptUtils",
                                "resource://gre/modules/SharedPromptUtils.jsm");
 ChromeUtils.defineModuleGetter(this, "Services",
                                "resource://gre/modules/Services.jsm");
 
 var RemotePrompt = {
   // Listeners are added in nsBrowserGlue.js
   receiveMessage(message) {

--- a/browser/modules/Windows8WindowFrameColor.jsm
+++ b/browser/modules/Windows8WindowFrameColor.jsm
@@ -1,18 +1,16 @@
 /* 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 EXPORTED_SYMBOLS = ["Windows8WindowFrameColor"];
 
-ChromeUtils.import("resource://gre/modules/Services.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 var Registry = ChromeUtils.import("resource://gre/modules/WindowsRegistry.jsm").WindowsRegistry;
 
 var Windows8WindowFrameColor = {
   _windowFrameColor: null,
 
   get() {
     if (this._windowFrameColor)
       return this._windowFrameColor;

--- a/browser/themes/shared/tabs.inc.css
+++ b/browser/themes/shared/tabs.inc.css
@@ -795,21 +795,16 @@
   display: block;
   margin-inline-end: 0;
 }
 
 .all-tabs-item[selected] {
   box-shadow: inset 4px 0 var(--blue-40);
 }
 
-.all-tabs-button,
-.all-tabs-secondary-button {
-  background-color: transparent !important;
-}
-
 .all-tabs-secondary-button > label {
   display: none;
   margin: 0 5.5px;
 }
 
 .all-tabs-secondary-button[soundplaying] {
   list-style-image: url(chrome://browser/skin/tabbrowser/tab-audio-playing.svg);
 }

--- a/browser/tools/mozscreenshots/mozscreenshots/extension/TestRunner.jsm
+++ b/browser/tools/mozscreenshots/mozscreenshots/extension/TestRunner.jsm
@@ -9,17 +9,16 @@ var EXPORTED_SYMBOLS = ["TestRunner"];
 const env = Cc["@mozilla.org/process/environment;1"].getService(Ci.nsIEnvironment);
 const APPLY_CONFIG_TIMEOUT_MS = 60 * 1000;
 const HOME_PAGE = "chrome://mozscreenshots/content/lib/mozscreenshots.html";
 
 ChromeUtils.import("resource://gre/modules/AppConstants.jsm");
 ChromeUtils.import("resource://gre/modules/FileUtils.jsm");
 ChromeUtils.import("resource://gre/modules/Services.jsm");
 ChromeUtils.import("resource://gre/modules/Timer.jsm");
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://gre/modules/osfile.jsm");
 ChromeUtils.import("resource://gre/modules/Geometry.jsm");
 
 ChromeUtils.defineModuleGetter(this, "BrowserTestUtils",
                                "resource://testing-common/BrowserTestUtils.jsm");
 // Screenshot.jsm must be imported this way for xpcshell tests to work
 ChromeUtils.defineModuleGetter(this, "Screenshot", "chrome://mozscreenshots/content/Screenshot.jsm");
 

--- a/browser/tools/mozscreenshots/mozscreenshots/extension/bootstrap.js
+++ b/browser/tools/mozscreenshots/mozscreenshots/extension/bootstrap.js
@@ -1,19 +1,17 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 /* exported install, uninstall, startup, shutdown */
 
 "use strict";
 
-ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 ChromeUtils.import("resource://gre/modules/AddonManager.jsm");
-ChromeUtils.import("resource://gre/modules/Services.jsm");
 ChromeUtils.import("resource://gre/modules/Timer.jsm");
 
 ChromeUtils.defineModuleGetter(this, "TestRunner",
                                "chrome://mozscreenshots/content/TestRunner.jsm");
 
 async function install(data, reason) {
   if (!isAppSupported()) {
     uninstallExtension(data);

--- a/devtools/.eslintrc.js
+++ b/devtools/.eslintrc.js
@@ -195,16 +195,17 @@ module.exports = {
     "react/no-did-mount-set-state": "error",
     "react/no-did-update-set-state": "error",
     "react/no-direct-mutation-state": "error",
     "react/no-unknown-property": "error",
     "react/prefer-es6-class": ["off", "always"],
     "react/prop-types": "error",
     "react/sort-comp": ["error", {
       order: [
+        "static-methods",
         "lifecycle",
         "everything-else",
         "render"
       ],
       groups: {
         lifecycle: [
           "displayName",
           "propTypes",

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/aboutdebugging.css
@@ -0,0 +1,24 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+@import "resource://devtools/client/themes/variables.css";
+@import "resource://devtools/client/aboutdebugging-new/src/components/App.css";
+@import "resource://devtools/client/aboutdebugging-new/src/components/RuntimesPane.css";
+@import "resource://devtools/client/aboutdebugging-new/src/components/runtime/RuntimeItem.css";
+
+:root {
+  --runtime-item-icon-color: var(--grey-30);
+  --runtime-item-selected-color: var(--blue-55);
+}
+
+html, body {
+  margin: 0;
+  padding: 0;
+}
+
+ul {
+  list-style: none;
+  margin: 0;
+  padding: 0;
+}

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/aboutdebugging.js
@@ -0,0 +1,65 @@
+/* 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 { BrowserLoader } =
+  ChromeUtils.import("resource://devtools/client/shared/browser-loader.js", {});
+const { require } = BrowserLoader({
+  baseURI: "resource://devtools/client/aboutdebugging-new/",
+  window,
+});
+const Services = require("Services");
+
+const { bindActionCreators } = require("devtools/client/shared/vendor/redux");
+const { createFactory } =
+  require("devtools/client/shared/vendor/react");
+const { render, unmountComponentAtNode } =
+  require("devtools/client/shared/vendor/react-dom");
+const Provider =
+  createFactory(require("devtools/client/shared/vendor/react-redux").Provider);
+
+const actions = require("./src/actions/index");
+const { configureStore } = require("./src/create-store");
+const ThisFirefox = require("./src/runtimes/this-firefox");
+
+const App = createFactory(require("./src/components/App"));
+
+const AboutDebugging = {
+  init() {
+    if (!Services.prefs.getBoolPref("devtools.enabled", true)) {
+      // If DevTools are disabled, navigate to about:devtools.
+      window.location = "about:devtools?reason=AboutDebugging";
+      return;
+    }
+
+    this.store = configureStore();
+    this.actions = bindActionCreators(actions, this.store.dispatch);
+
+    const thisFirefox = new ThisFirefox();
+    this.updateSelectedRuntime(thisFirefox);
+
+    render(Provider({ store: this.store }, App({ thisFirefox })), this.mount);
+  },
+
+  destroy() {
+    unmountComponentAtNode(this.mount);
+  },
+
+  get mount() {
+    return document.getElementById("mount");
+  },
+
+  updateSelectedRuntime(runtime) {
+    this.actions.updateSelectedRuntime(runtime);
+  },
+};
+
+window.addEventListener("DOMContentLoaded", () => {
+  AboutDebugging.init();
+}, { once: true });
+
+window.addEventListener("unload", () => {
+  AboutDebugging.destroy();
+}, {once: true});

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/index.html
@@ -0,0 +1,14 @@
+<!-- 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/. -->
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8" />
+    <link rel="stylesheet" href="chrome://devtools/content/aboutdebugging-new/aboutdebugging.css"/>
+    <script src="chrome://devtools/content/aboutdebugging-new/aboutdebugging.js"></script>
+  </head>
+  <body>
+    <div id="mount"></div>
+  </body>
+</html>

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/moz.build
@@ -0,0 +1,10 @@
+# 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/.
+
+DIRS += [
+    'src',
+]
+
+with Files('**'):
+    BUG_COMPONENT = ('DevTools', 'about:debugging')
\ No newline at end of file

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/actions/index.js
@@ -0,0 +1,9 @@
+/* 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 runtimes = require("./runtimes");
+
+Object.assign(exports, runtimes);

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/actions/moz.build
@@ -0,0 +1,8 @@
+# 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/.
+
+DevToolsModules(
+    'index.js',
+    'runtimes.js',
+)

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/actions/runtimes.js
@@ -0,0 +1,20 @@
+/* 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 {
+  UPDATE_SELECTED_RUNTIME,
+} = require("../constants");
+
+function updateSelectedRuntime(runtime) {
+  return {
+    type: UPDATE_SELECTED_RUNTIME,
+    runtime,
+  };
+}
+
+module.exports = {
+  updateSelectedRuntime,
+};

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/components/App.css
@@ -0,0 +1,10 @@
+/* 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/. */
+
+.app {
+  font-size: 15px;
+  height: 100vh;
+  overflow: hidden;
+  width: 100vw;
+}

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/components/App.js
@@ -0,0 +1,43 @@
+/* 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 { connect } = require("devtools/client/shared/vendor/react-redux");
+const { createFactory, PureComponent } = require("devtools/client/shared/vendor/react");
+const dom = require("devtools/client/shared/vendor/react-dom-factories");
+const PropTypes = require("devtools/client/shared/vendor/react-prop-types");
+
+const Runtime = require("../runtimes/runtime");
+const ThisFirefox = require("../runtimes/this-firefox");
+
+const RuntimesPane = createFactory(require("./RuntimesPane"));
+
+class App extends PureComponent {
+  static get propTypes() {
+    return {
+      selectedRuntime: PropTypes.instanceOf(Runtime),
+      thisFirefox: PropTypes.instanceOf(ThisFirefox).isRequired,
+    };
+  }
+
+  render() {
+    const { selectedRuntime, thisFirefox } = this.props;
+
+    return dom.div(
+      {
+        className: "app",
+      },
+      RuntimesPane({ selectedRuntime, thisFirefox })
+    );
+  }
+}
+
+const mapStateToProps = state => {
+  return {
+    selectedRuntime: state.runtimes.selectedRuntime,
+  };
+};
+
+module.exports = connect(mapStateToProps)(App);

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/components/RuntimesPane.css
@@ -0,0 +1,8 @@
+/* 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/. */
+
+.runtimes-pane {
+  margin-block-start: 70px;
+  width: 240px;
+}

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/components/RuntimesPane.js
@@ -0,0 +1,43 @@
+/* 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 { createFactory, PureComponent } = require("devtools/client/shared/vendor/react");
+const dom = require("devtools/client/shared/vendor/react-dom-factories");
+const PropTypes = require("devtools/client/shared/vendor/react-prop-types");
+
+const ThisFirefox = require("../runtimes/this-firefox");
+
+const Runtime = require("../runtimes/runtime");
+const RuntimeItem = createFactory(require("./runtime/RuntimeItem"));
+
+class RuntimesPane extends PureComponent {
+  static get propTypes() {
+    return {
+      selectedRuntime: PropTypes.instanceOf(Runtime),
+      thisFirefox: PropTypes.instanceOf(ThisFirefox).isRequired,
+    };
+  }
+
+  render() {
+    const { selectedRuntime, thisFirefox } = this.props;
+
+    return dom.section(
+      {
+        className: "runtimes-pane",
+      },
+      dom.ul(
+        {},
+        RuntimeItem({
+          icon: thisFirefox.getIcon(),
+          isSelected: thisFirefox === selectedRuntime,
+          name: thisFirefox.getName(),
+        })
+      )
+    );
+  }
+}
+
+module.exports = RuntimesPane;

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/components/moz.build
@@ -0,0 +1,14 @@
+# 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/.
+
+DIRS += [
+    'runtime',
+]
+
+DevToolsModules(
+    'App.css',
+    'App.js',
+    'RuntimesPane.css',
+    'RuntimesPane.js'
+)

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/components/runtime/RuntimeItem.css
@@ -0,0 +1,26 @@
+/* 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/. */
+
+.runtime-item {
+  align-items: center;
+  display: flex;
+  font-size: 20px;
+  margin-inline-start: 24px;
+}
+
+.runtime-item__icon {
+  fill: var(--runtime-item-icon-color);
+  height: 24px;
+  margin-inline-end: 9px;
+  width: 24px;
+  -moz-context-properties: fill;
+}
+
+.runtime-item--selected {
+  color: var(--runtime-item-selected-color);
+}
+
+.runtime-item__icon--selected {
+  fill: var(--runtime-item-selected-color);
+}

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/components/runtime/RuntimeItem.js
@@ -0,0 +1,40 @@
+/* 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 { PureComponent } = require("devtools/client/shared/vendor/react");
+const dom = require("devtools/client/shared/vendor/react-dom-factories");
+const PropTypes = require("devtools/client/shared/vendor/react-prop-types");
+
+/**
+ * This component shows the runtime as item in RuntimesPane.
+ */
+class RuntimeItem extends PureComponent {
+  static get propTypes() {
+    return {
+      icon: PropTypes.string.isRequired,
+      isSelected: PropTypes.bool.isRequired,
+      name: PropTypes.string.isRequired,
+    };
+  }
+
+  render() {
+    const { icon, isSelected, name } = this.props;
+
+    return dom.li(
+      {
+        className: "runtime-item" + (isSelected ? " runtime-item--selected" : ""),
+      },
+      dom.img({
+        className: "runtime-item__icon" +
+                   (isSelected ? " runtime-item__icon--selected" : ""),
+        src: icon,
+      }),
+      name
+    );
+  }
+}
+
+module.exports = RuntimeItem;

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/components/runtime/moz.build
@@ -0,0 +1,8 @@
+# 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/.
+
+DevToolsModules(
+    'RuntimeItem.css',
+    'RuntimeItem.js',
+)

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/constants.js
@@ -0,0 +1,11 @@
+/* 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 actionTypes = {
+  UPDATE_SELECTED_RUNTIME: "UPDATE_SELECTED_RUNTIME",
+};
+
+module.exports = Object.assign({}, actionTypes);

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/create-store.js
@@ -0,0 +1,18 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { createStore } = require("devtools/client/shared/vendor/redux");
+
+const rootReducer = require("./reducers/index");
+const { RuntimesState } = require("./reducers/runtimes-state");
+
+exports.configureStore = function() {
+  const initialState = {
+    runtimes: new RuntimesState(),
+  };
+
+  return createStore(rootReducer, initialState);
+};

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/moz.build
@@ -0,0 +1,15 @@
+# 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/.
+
+DIRS += [
+    'actions',
+    'components',
+    'runtimes',
+    'reducers',
+]
+
+DevToolsModules(
+    'constants.js',
+    'create-store.js'
+)

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/reducers/index.js
@@ -0,0 +1,12 @@
+/* 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 { combineReducers } = require("devtools/client/shared/vendor/redux");
+const { runtimesReducer } = require("./runtimes-state");
+
+module.exports = combineReducers({
+  runtimes: runtimesReducer,
+});

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/reducers/moz.build
@@ -0,0 +1,8 @@
+# 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/.
+
+DevToolsModules(
+    'index.js',
+    'runtimes-state.js',
+)

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/reducers/runtimes-state.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";
+
+const {
+  UPDATE_SELECTED_RUNTIME,
+} = require("../constants");
+
+function RuntimesState() {
+  return {
+    selectedRuntime: null,
+  };
+}
+
+function runtimesReducer(state = RuntimesState(), action) {
+  switch (action.type) {
+    case UPDATE_SELECTED_RUNTIME: {
+      return Object.assign({}, state, {
+        selectedRuntime: action.runtime,
+      });
+    }
+
+    default:
+      return state;
+  }
+}
+
+module.exports = {
+  RuntimesState,
+  runtimesReducer,
+};

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/runtimes/moz.build
@@ -0,0 +1,8 @@
+# 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/.
+
+DevToolsModules(
+    'runtime.js',
+    'this-firefox.js',
+)

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/runtimes/runtime.js
@@ -0,0 +1,30 @@
+/* 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 class represents a runtime, such as a remote Firefox.
+ */
+class Runtime {
+  /**
+   * Return icon of this runtime on sidebar.
+   * Subclass should override this method.
+   * @return {String}
+   */
+  getIcon() {
+    throw new Error("Subclass of Runtime should override getIcon()");
+  }
+
+  /**
+   * Return name of this runtime on sidebar.
+   * Subclass should override this method.
+   * @return {String}
+   */
+  getName() {
+    throw new Error("Subclass of Runtime should override getName()");
+  }
+}
+
+module.exports = Runtime;

new file mode 100644
--- /dev/null
+++ b/devtools/client/aboutdebugging-new/src/runtimes/this-firefox.js
@@ -0,0 +1,23 @@
+/* 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 Runtime = require("./runtime");
+
+/**
+ * This class represents the Firefox instance which runs in the same environment that
+ * opened about:debugging.
+ */
+class ThisFirefox extends Runtime {
+  getIcon() {
+    return "chrome://devtools/skin/images/firefox-logo-glyph.svg";
+  }
+
+  getName() {
+    return "This Firefox";
+  }
+}
+
+module.exports = ThisFirefox;

--- a/devtools/client/debugger/test/mochitest/browser2.ini
+++ b/devtools/client/debugger/test/mochitest/browser2.ini
@@ -395,17 +395,16 @@ skip-if = e10s && debug
 [browser_dbg_stack-contextmenu-02.js]
 uses-unsafe-cpows = true
 subsuite = clipboard
 skip-if = (e10s && debug) || (os == 'linux' && bits == 32 && debug) # bug 1328915, disable linux32 debug devtools for timeouts
 [browser_dbg_step-out.js]
 uses-unsafe-cpows = true
 skip-if = e10s && debug
 [browser_dbg_target-scoped-actor-01.js]
-skip-if = e10s # TODO
 [browser_dbg_target-scoped-actor-02.js]
 skip-if = e10s # TODO
 [browser_dbg_terminate-on-tab-close.js]
 uses-unsafe-cpows = true
 skip-if = e10s && debug
 [browser_dbg_variables-view-01.js]
 uses-unsafe-cpows = true
 skip-if = e10s && debug

--- a/devtools/client/debugger/test/mochitest/browser_dbg_target-scoped-actor-01.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_target-scoped-actor-01.js
@@ -5,63 +5,40 @@
 
 /**
  * Check target-scoped actor lifetimes.
  */
 
 const ACTORS_URL = CHROME_URL + "testactors.js";
 const TAB_URL = EXAMPLE_URL + "doc_empty-tab-01.html";
 
-var gClient;
+add_task(async function test() {
+  await addTab(TAB_URL);
 
-function test() {
   DebuggerServer.init();
   DebuggerServer.registerAllActors();
 
-  DebuggerServer.registerModule(ACTORS_URL, {
+  await registerActorInContentProcess(ACTORS_URL, {
     prefix: "testOne",
     constructor: "TestActor1",
     type: { target: true },
   });
 
-  let transport = DebuggerServer.connectPipe();
-  gClient = new DebuggerClient(transport);
-  gClient.connect().then(([aType, aTraits]) => {
-    is(aType, "browser",
-      "Root actor should identify itself as a browser.");
+  const transport = DebuggerServer.connectPipe();
+  const client = new DebuggerClient(transport);
+  const [ type ] = await client.connect();
+  is(type, "browser", "Root actor should identify itself as a browser.");
 
-    addTab(TAB_URL)
-      .then(() => attachTargetActorForUrl(gClient, TAB_URL))
-      .then(testTargetScopedActor)
-      .then(closeTab)
-      .then(() => gClient.close())
-      .then(finish)
-      .catch(aError => {
-        ok(false, "Got an error: " + aError.message + "\n" + aError.stack);
-      });
-  });
-}
+  const [ grip ] = await attachTargetActorForUrl(client, TAB_URL);
+  await testTargetScopedActor(client, grip);
+  await removeTab(gBrowser.selectedTab);
+  await client.close();
+});
 
-function testTargetScopedActor([aGrip, aResponse]) {
-  let deferred = promise.defer();
-
-  ok(aGrip.testOneActor,
+async function testTargetScopedActor(client, grip) {
+  ok(grip.testOneActor,
     "Found the test target-scoped actor.");
-  ok(aGrip.testOneActor.includes("testOne"),
+  ok(grip.testOneActor.includes("testOne"),
     "testOneActor's actorPrefix should be used.");
 
-  gClient.request({ to: aGrip.testOneActor, type: "ping" }, aResponse => {
-    is(aResponse.pong, "pong",
-      "Actor should respond to requests.");
-
-    deferred.resolve();
-  });
-
-  return deferred.promise;
+  const response = await client.request({ to: grip.testOneActor, type: "ping" });
+  is(response.pong, "pong", "Actor should respond to requests.");
 }
-
-function closeTab() {
-  return removeTab(gBrowser.selectedTab);
-}
-
-registerCleanupFunction(function () {
-  gClient = null;
-});

--- a/devtools/client/inspector/markup/test/browser.ini
+++ b/devtools/client/inspector/markup/test/browser.ini
@@ -174,16 +174,17 @@ subsuite = clipboard
 [browser_markup_shadowdom_hover.js]
 [browser_markup_shadowdom_maxchildren.js]
 [browser_markup_shadowdom_mutations_shadow.js]
 [browser_markup_shadowdom_navigation.js]
 [browser_markup_shadowdom_nested_pick_inspect.js]
 [browser_markup_shadowdom_noslot.js]
 [browser_markup_shadowdom_open_debugger.js]
 [browser_markup_shadowdom_shadowroot_mode.js]
+[browser_markup_shadowdom_show_nodes_button.js]
 [browser_markup_shadowdom_slotupdate.js]
 [browser_markup_tag_delete_whitespace_node.js]
 [browser_markup_tag_edit_01.js]
 [browser_markup_tag_edit_02.js]
 [browser_markup_tag_edit_03.js]
 [browser_markup_tag_edit_04-backspace.js]
 [browser_markup_tag_edit_04-delete.js]
 [browser_markup_tag_edit_05.js]

new file mode 100644
--- /dev/null
+++ b/devtools/client/inspector/markup/test/browser_markup_shadowdom_show_nodes_button.js
@@ -0,0 +1,52 @@
+/* Any copyright is dedicated to the Public Domain.
+ http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// Test that the "Show all 'N' nodes" button displays the proper value
+
+const NODE_COUNT = 101;
+const TEST_URL = `data:text/html;charset=utf-8,
+  <test-component>
+  </test-component>
+
+  <script>
+    'use strict';
+    for (let i = 0; i < ${NODE_COUNT}; i++) {
+      const div = document.createElement("div");
+      div.innerHTML = i;
+      document.querySelector('test-component').appendChild(div);
+    }
+    customElements.define('test-component', class extends HTMLElement {
+      constructor() {
+        super();
+        let shadowRoot = this.attachShadow({mode: 'open'});
+        shadowRoot.innerHTML = '<slot></slot>';
+      }
+    });
+  </script>`;
+
+add_task(async function() {
+  await enableWebComponents();
+
+  const { inspector } = await openInspectorForURL(TEST_URL);
+  const { markup } = inspector;
+
+  info("Find and expand the component shadow DOM host.");
+  const hostFront = await getNodeFront("test-component", inspector);
+  const hostContainer = markup.getContainer(hostFront);
+  await expandContainer(inspector, hostContainer);
+  const shadowRootContainer = hostContainer.getChildContainers()[0];
+  await expandContainer(inspector, shadowRootContainer);
+
+  info("Expand the slot");
+  const slotContainer = shadowRootContainer.getChildContainers()[0];
+  await expandContainer(inspector, slotContainer);
+
+  info("Find the 'Show all nodes' button");
+  const button = slotContainer.elt.querySelector("button");
+  console.log(button);
+  ok(button.innerText.includes(NODE_COUNT),
+    "'Show all nodes' button contains correct node count");
+});
+

--- a/devtools/client/jar.mn
+++ b/devtools/client/jar.mn
@@ -83,16 +83,19 @@ devtools.jar:
     content/framework/connect/connect.css (framework/connect/connect.css)
     content/framework/connect/connect.js (framework/connect/connect.js)
     content/shared/widgets/graphs-frame.xhtml (shared/widgets/graphs-frame.xhtml)
     content/shared/widgets/cubic-bezier.css (shared/widgets/cubic-bezier.css)
     content/shared/widgets/filter-widget.css (shared/widgets/filter-widget.css)
     content/shared/widgets/spectrum.css (shared/widgets/spectrum.css)
     content/aboutdebugging/aboutdebugging.xhtml (aboutdebugging/aboutdebugging.xhtml)
     content/aboutdebugging/aboutdebugging.css (aboutdebugging/aboutdebugging.css)
+    content/aboutdebugging-new/index.html (aboutdebugging-new/index.html)
+    content/aboutdebugging-new/aboutdebugging.css (aboutdebugging-new/aboutdebugging.css)
+    content/aboutdebugging-new/aboutdebugging.js (aboutdebugging-new/aboutdebugging.js)
     content/responsive.html/index.xhtml (responsive.html/index.xhtml)
     content/dom/index.html (dom/index.html)
     content/dom/main.js (dom/main.js)
     content/accessibility/index.html (accessibility/index.html)
     content/accessibility/main.js (accessibility/main.js)
 %   skin devtools classic/1.0 %skin/
     skin/devtools-browser.css (themes/devtools-browser.css)
     skin/dark-theme.css (themes/dark-theme.css)
@@ -100,16 +103,17 @@ devtools.jar:
     skin/toolbars.css (themes/toolbars.css)
     skin/toolbox.css (themes/toolbox.css)
     skin/tooltips.css (themes/tooltips.css)
     skin/images/accessibility.svg (themes/images/accessibility.svg)
     skin/images/add.svg (themes/images/add.svg)
     skin/images/breadcrumbs-divider.svg (themes/images/breadcrumbs-divider.svg)
     skin/images/filters.svg (themes/images/filters.svg)
     skin/images/filter-swatch.svg (themes/images/filter-swatch.svg)
+    skin/images/firefox-logo-glyph.svg (themes/images/firefox-logo-glyph.svg)
     skin/images/fox-smiling.svg (themes/images/fox-smiling.svg)
     skin/images/grid.svg (themes/images/grid.svg)
     skin/images/angle-swatch.svg (themes/images/angle-swatch.svg)
     skin/images/pseudo-class.svg (themes/images/pseudo-class.svg)
     skin/images/controls.png (themes/images/controls.png)
     skin/images/controls@2x.png (themes/images/controls@2x.png)
     skin/images/copy.svg (themes/images/copy.svg)
     skin/images/animation-fast-track.svg (themes/images/animation-fast-track.svg)

--- a/devtools/client/memory/app.js
+++ b/devtools/client/memory/app.js
@@ -50,17 +50,31 @@ const { resizeShortestPaths } = require(
 const Toolbar = createFactory(require("./components/Toolbar"));
 const List = createFactory(require("./components/List"));
 const SnapshotListItem = createFactory(require("./components/SnapshotListItem"));
 const Heap = createFactory(require("./components/Heap"));
 const { app: appModel } = require("./models");
 
 class MemoryApp extends Component {
   static get propTypes() {
-    return appModel;
+    return {
+      allocations: appModel.allocations,
+      censusDisplay: appModel.censusDisplay,
+      diffing: appModel.diffing,
+      dispatch: appModel.dispatch,
+      filter: appModel.filter,
+      front: appModel.front,
+      heapWorker: appModel.heapWorker,
+      individuals: appModel.individuals,
+      labelDisplay: appModel.labelDisplay,
+      sizes: appModel.sizes,
+      snapshots: appModel.snapshots,
+      toolbox: appModel.toolbox,
+      view: appModel.view,
+    };
   }
 
   static get childContextTypes() {
     return {
       front: PropTypes.any,
       heapWorker: PropTypes.any,
       toolbox: PropTypes.any,
     };

--- a/devtools/client/moz.build
+++ b/devtools/client/moz.build
@@ -3,16 +3,17 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 include('../templates.mozbuild')
 
 DIRS += [
     'aboutdebugging',
+    'aboutdebugging-new',
     'accessibility',
     'application',
     'canvasdebugger',
     'commandline',
     'debugger',
     'dom',
     'framework',
     'inspector',

--- a/devtools/client/preferences/devtools-client.js
+++ b/devtools/client/preferences/devtools-client.js
@@ -308,14 +308,17 @@ pref("devtools.editor.autocomplete", tru
 
 // Whether to reload when touch simulation is toggled
 pref("devtools.responsive.reloadConditions.touchSimulation", false);
 // Whether to reload when user agent is changed
 pref("devtools.responsive.reloadConditions.userAgent", false);
 // Whether to show the notification about reloading to apply emulation
 pref("devtools.responsive.reloadNotification.enabled", true);
 
+// Enable new about:debugging.
+pref("devtools.aboutdebugging.new-enabled", false);
+
 // about:debugging: only show system add-ons in local builds by default.
 #ifdef MOZILLA_OFFICIAL
   pref("devtools.aboutdebugging.showSystemAddons", false);
 #else
   pref("devtools.aboutdebugging.showSystemAddons", true);
 #endif

--- a/devtools/client/shared/components/tree/TreeView.js
+++ b/devtools/client/shared/components/tree/TreeView.js
@@ -129,61 +129,16 @@ define(function(require, exports, module
         }))
       };
     }
 
     static get defaultProps() {
       return defaultProps;
     }
 
-    constructor(props) {
-      super(props);
-
-      this.state = {
-        expandedNodes: props.expandedNodes,
-        columns: ensureDefaultColumn(props.columns),
-        selected: props.selected,
-        lastSelectedIndex: 0
-      };
-
-      this.toggle = this.toggle.bind(this);
-      this.isExpanded = this.isExpanded.bind(this);
-      this.onKeyDown = this.onKeyDown.bind(this);
-      this.onClickRow = this.onClickRow.bind(this);
-      this.getSelectedRow = this.getSelectedRow.bind(this);
-      this.selectRow = this.selectRow.bind(this);
-      this.isSelected = this.isSelected.bind(this);
-      this.onFilter = this.onFilter.bind(this);
-      this.onSort = this.onSort.bind(this);
-      this.getMembers = this.getMembers.bind(this);
-      this.renderRows = this.renderRows.bind(this);
-    }
-
-    componentWillReceiveProps(nextProps) {
-      const { expandedNodes, selected } = nextProps;
-      const state = {
-        expandedNodes,
-        lastSelectedIndex: this.getSelectedRowIndex()
-      };
-
-      if (selected) {
-        state.selected = selected;
-      }
-
-      this.setState(Object.assign({}, this.state, state));
-    }
-
-    componentDidUpdate() {
-      const selected = this.getSelectedRow();
-      if (!selected && this.rows.length > 0) {
-        this.selectRow(this.rows[
-          Math.min(this.state.lastSelectedIndex, this.rows.length - 1)]);
-      }
-    }
-
     static subPath(path, subKey) {
       return path + "/" + String(subKey).replace(/[\\/]/g, "\\$&");
     }
 
     /**
      * Creates a set with the paths of the nodes that should be expanded by default
      * according to the passed options.
      * @param {Object} The root node of the tree.
@@ -221,16 +176,61 @@ define(function(require, exports, module
               path: nodePath
             });
           }
         }
       }
       return expandedNodes;
     }
 
+    constructor(props) {
+      super(props);
+
+      this.state = {
+        expandedNodes: props.expandedNodes,
+        columns: ensureDefaultColumn(props.columns),
+        selected: props.selected,
+        lastSelectedIndex: 0
+      };
+
+      this.toggle = this.toggle.bind(this);
+      this.isExpanded = this.isExpanded.bind(this);
+      this.onKeyDown = this.onKeyDown.bind(this);
+      this.onClickRow = this.onClickRow.bind(this);
+      this.getSelectedRow = this.getSelectedRow.bind(this);
+      this.selectRow = this.selectRow.bind(this);
+      this.isSelected = this.isSelected.bind(this);
+      this.onFilter = this.onFilter.bind(this);
+      this.onSort = this.onSort.bind(this);
+      this.getMembers = this.getMembers.bind(this);
+      this.renderRows = this.renderRows.bind(this);
+    }
+
+    componentWillReceiveProps(nextProps) {
+      const { expandedNodes, selected } = nextProps;
+      const state = {
+        expandedNodes,
+        lastSelectedIndex: this.getSelectedRowIndex()
+      };
+
+      if (selected) {
+        state.selected = selected;
+      }
+
+      this.setState(Object.assign({}, this.state, state));
+    }
+
+    componentDidUpdate() {
+      const selected = this.getSelectedRow();
+      if (!selected && this.rows.length > 0) {
+        this.selectRow(this.rows[
+          Math.min(this.state.lastSelectedIndex, this.rows.length - 1)]);
+      }
+    }
+
     // Node expand/collapse
 
     toggle(nodePath) {
       const nodes = this.state.expandedNodes;
       if (this.isExpanded(nodePath)) {
         nodes.delete(nodePath);
       } else {
         nodes.add(nodePath);

--- a/devtools/client/shared/test/shared-head.js
+++ b/devtools/client/shared/test/shared-head.js
@@ -725,8 +725,37 @@ async function injectEventUtilsInContent
 
 /**
  * Temporarily flip all the preferences needed to enable web components.
  */
 async function enableWebComponents() {
   await pushPref("dom.webcomponents.shadowdom.enabled", true);
   await pushPref("dom.webcomponents.customelements.enabled", true);
 }
+
+/*
+ * Register an actor in the content process of the current tab.
+ *
+ * Calling DebuggerServer.registerModule only registers the actor in the current process.
+ * As all test scripts are ran in the parent process, it is only registered here.
+ * This function helps register them in the content process used for the current tab.
+ *
+ * @param {string} url
+ *        Actor module URL or absolute require path
+ * @param {json} options
+ *        Arguments to be passed to DebuggerServer.registerModule
+ */
+async function registerActorInContentProcess(url, options) {
+  function convertChromeToFile(uri) {
+    return Cc["@mozilla.org/chrome/chrome-registry;1"]
+             .getService(Ci.nsIChromeRegistry)
+             .convertChromeURL(Services.io.newURI(uri)).spec;
+  }
+  // chrome://mochitests URI is registered only in the parent process, so convert these
+  // URLs to file:// one in order to work in the content processes
+  url = url.startsWith("chrome://mochitests") ? convertChromeToFile(url) : url;
+  return ContentTask.spawn(gBrowser.selectedBrowser, { url, options }, args => {
+    // eslint-disable-next-line no-shadow
+    const { require } = ChromeUtils.import("resource://devtools/shared/Loader.jsm", {});
+    const { DebuggerServer } = require("devtools/server/main");
+    DebuggerServer.registerModule(args.url, args.options);
+  });
+}

new file mode 100644
--- /dev/null
+++ b/devtools/client/themes/images/firefox-logo-glyph.svg
@@ -0,0 +1,7 @@
+<!-- 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/. -->
+<svg xmlns="http://www.w3.org/2000/svg" width="32" height="32" viewBox="0 0 32 32">
+  <path fill="context-fill"
+        d="M31.359,14.615h0c-.044-.289-.088-.459-.088-.459s-.113.131-.3.378A10.77,10.77,0,0,0,30.6,12.5a13.846,13.846,0,0,0-.937-2.411,10.048,10.048,0,0,0-.856-1.468q-.176-.263-.359-.51c-.57-.931-1.224-1.5-1.981-2.576a7.806,7.806,0,0,1-.991-2.685A10.844,10.844,0,0,0,25,4.607c-.777-.784-1.453-1.341-1.861-1.721C21.126,1.006,21.36.031,21.36.031h0S17.6,4.228,19.229,8.6a8.4,8.4,0,0,0,2.8,3.733c1.576,1.3,3.273,2.323,4.168,4.937a8.377,8.377,0,0,0-3.144-3.317,7.573,7.573,0,0,1,.6,3,7.124,7.124,0,0,1-8.711,6.94,6.561,6.561,0,0,1-1.765-.6,7.183,7.183,0,0,1-2.115-1.955l-.01-.017.126.046a6.5,6.5,0,0,0,.9.241,5.628,5.628,0,0,0,3.583-.423c1.126-.625,1.808-1.088,2.361-.905l.01,0c.54.172.966-.352.58-.9a2.94,2.94,0,0,0-2.848-1.112c-1.127.164-2.16.965-3.637.189a3.129,3.129,0,0,1-.277-.163c-.1-.057.317.087.22.022a7.33,7.33,0,0,1-.928-.554c-.022-.018.223.07.2.052a3.581,3.581,0,0,1-.968-.979,1.741,1.741,0,0,1-.066-1.554,1.371,1.371,0,0,1,.6-.564c.191.094.309.165.309.165s-.087-.16-.134-.244c.017-.006.032,0,.049-.011.167.072.537.26.732.375a1.016,1.016,0,0,1,.335.3s.067-.033.017-.173a.9.9,0,0,0-.346-.424l.016,0a2.94,2.94,0,0,1,.426.265,2.079,2.079,0,0,0,.17-.9,1.178,1.178,0,0,0-.069-.5c-.053-.1.03-.14.123-.035a.976.976,0,0,0-.079-.238v-.008h0s.053-.069.077-.094a1.43,1.43,0,0,1,.216-.176,9.973,9.973,0,0,1,1.465-.747c.414-.181.757-.319.827-.359a2.3,2.3,0,0,0,.293-.225,1.968,1.968,0,0,0,.66-1.14,1.6,1.6,0,0,0,.017-.178v-.05l0-.03v0l0-.012v0l0-.013h0c-.06-.225-.448-.394-2.476-.584a1.773,1.773,0,0,1-1.45-1.36l0,.009c-.029.074-.055.149-.081.225.026-.075.052-.15.081-.225l0-.016a5.138,5.138,0,0,1,1.986-2.466c.052-.042-.208.011-.156-.032a5.156,5.156,0,0,1,.53-.224c.091-.038-.39-.222-.815-.177a2.2,2.2,0,0,0-.756.178c.1-.086.4-.2.329-.2a4.865,4.865,0,0,0-1.542.583.314.314,0,0,1,.03-.14,2.4,2.4,0,0,0-.964.744,1.275,1.275,0,0,0,.01-.174,2.876,2.876,0,0,0-.473.444l-.009.007a6.285,6.285,0,0,0-3.517-.3l-.01-.009.012,0a2.943,2.943,0,0,1-.625-.7L6.1,5.852,6.081,5.83c-.077-.114-.156-.243-.237-.387-.058-.1-.117-.217-.176-.338,0-.008-.009-.011-.013-.012-.024,0-.041.111-.061.082l0-.006a4.308,4.308,0,0,1-.283-1.687l-.016.008a1.884,1.884,0,0,0-.714.934c-.061.137-.1.212-.14.287,0,.006,0-.01,0-.035.009-.069.039-.211.032-.2s-.012.019-.019.029a1.733,1.733,0,0,0-.251.372,2.355,2.355,0,0,0-.15.382c-.006.021,0-.018,0-.064s.009-.128,0-.111l-.022.043a9.5,9.5,0,0,0-.8,3.035A3.022,3.022,0,0,0,3.2,8.7v.016a6.628,6.628,0,0,0-.817,1.1,15.606,15.606,0,0,0-1.727,4.23,10.351,10.351,0,0,1,.925-1.621,15,15,0,0,0-1.045,5.5,14.233,14.233,0,0,1,.45-1.629A13.807,13.807,0,0,0,2.234,22.76a15.037,15.037,0,0,0,5.951,6.748h0a13.016,13.016,0,0,0,3.468,1.662c.162.059.326.117.494.173-.053-.021-.1-.044-.153-.067a15.7,15.7,0,0,0,4.5.662c5.394,0,7.175-2.054,7.339-2.259h0a2.73,2.73,0,0,0,.637-.856h0q.156-.064.315-.137l.067-.03.121-.057a11.312,11.312,0,0,0,2.277-1.426,5.5,5.5,0,0,0,2.123-3.1h0a1.938,1.938,0,0,0,.029-1.428q.083-.131.171-.28a12.706,12.706,0,0,0,1.907-6.181v-.006c0-.059,0-.118,0-.177A7.731,7.731,0,0,0,31.359,14.615Z"/>
+</svg>

new file mode 100644
--- /dev/null
+++ b/devtools/client/webconsole/middleware/event-telemetry.js
@@ -0,0 +1,80 @@
+/* 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";
+
+const {
+  FILTER_TEXT_SET,
+  FILTER_TOGGLE,
+  DEFAULT_FILTERS_RESET,
+} = require("devtools/client/webconsole/constants");
+
+/**
+ * Event telemetry middleware is responsible for logging specific events to telemetry.
+ */
+function eventTelemetryMiddleware(telemetry, sessionId, store) {
+  return next => action => {
+    const oldState = store.getState();
+    const res = next(action);
+    if (!sessionId) {
+      return res;
+    }
+
+    const state = store.getState();
+
+    const filterChangeActions = [
+      FILTER_TEXT_SET,
+      FILTER_TOGGLE,
+      DEFAULT_FILTERS_RESET,
+    ];
+
+    if (filterChangeActions.includes(action.type)) {
+      filterChange({
+        action,
+        state,
+        oldState,
+        telemetry,
+        sessionId
+      });
+    }
+
+    return res;
+  };
+}
+
+function filterChange({action, state, oldState, telemetry, sessionId}) {
+  const oldFilterState = oldState.filters;
+  const filterState = state.filters;
+  const activeFilters = [];
+  const inactiveFilters = [];
+  for (const [key, value] of Object.entries(filterState)) {
+    if (value) {
+      activeFilters.push(key);
+    } else {
+      inactiveFilters.push(key);
+    }
+  }
+
+  let trigger;
+  if (action.type === FILTER_TOGGLE) {
+    trigger = action.filter;
+  } else if (action.type === DEFAULT_FILTERS_RESET) {
+    trigger = "reset";
+  } else if (action.type === FILTER_TEXT_SET) {
+    if (oldFilterState.text !== "" && filterState.text !== "") {
+      return;
+    }
+
+    trigger = "text";
+  }
+
+  telemetry.recordEvent("devtools.main", "filters_changed", "webconsole", null, {
+    "trigger": trigger,
+    "active": activeFilters.join(","),
+    "inactive": inactiveFilters.join(","),
+    "session_id": sessionId
+  });
+}
+
+module.exports = eventTelemetryMiddleware;

--- a/devtools/client/webconsole/middleware/moz.build
+++ b/devtools/client/webconsole/middleware/moz.build
@@ -1,9 +1,10 @@
 # vim: set filetype=python:
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 DevToolsModules(
+    'event-telemetry.js',
     'history-persistence.js',
     'thunk.js',
 )

--- a/devtools/client/webconsole/store.js
+++ b/devtools/client/webconsole/store.js
@@ -18,16 +18,17 @@ const {
 // Prefs
 const { PREFS } = require("devtools/client/webconsole/constants");
 const { getPrefsService } = require("devtools/client/webconsole/utils/prefs");
 
 // Reducers
 const { reducers } = require("./reducers/index");
 
 // Middleware
+const eventTelemetry = require("./middleware/event-telemetry");
 const historyPersistence = require("./middleware/history-persistence");
 const thunk = require("./middleware/thunk");
 
 // Enhancers
 const enableBatching = require("./enhancers/batching");
 const enableActorReleaser = require("./enhancers/actor-releaser");
 const ensureCSSErrorReportingEnabled = require("./enhancers/css-error-reporting");
 const enableNetProvider = require("./enhancers/net-provider");
@@ -73,16 +74,17 @@ function configureStore(hud, options = {
       persistLogs: getBoolPref(PREFS.UI.PERSIST),
     })
   };
 
   // Prepare middleware.
   const middleware = applyMiddleware(
     thunk.bind(null, {prefsService}),
     historyPersistence,
+    eventTelemetry.bind(null, options.telemetry, options.sessionId),
   );
 
   return createStore(
     createRootReducer(),
     initialState,
     compose(
       middleware,
       enableActorReleaser(hud),

--- a/devtools/client/webconsole/test/helpers.js
+++ b/devtools/client/webconsole/test/helpers.js
@@ -6,16 +6,17 @@
 const reduxActions = require("devtools/client/webconsole/actions/index");
 const { configureStore } = require("devtools/client/webconsole/store");
 const { IdGenerator } = require("devtools/client/webconsole/utils/id-generator");
 const { stubPackets } = require("devtools/client/webconsole/test/fixtures/stubs/index");
 const { getAllMessagesById } = require("devtools/client/webconsole/selectors/messages");
 const { getPrefsService } = require("devtools/client/webconsole/utils/prefs");
 const prefsService = getPrefsService({});
 const { PREFS } = require("devtools/client/webconsole/constants");
+const Telemetry = require("devtools/client/shared/telemetry");
 
 /**
  * Prepare actions for use in testing.
  */
 function setupActions() {
   // Some actions use dependency injection. This helps them avoid using state in
   // a hard-to-test way. We need to inject stubbed versions of these dependencies.
   const wrappedActions = Object.assign({}, reduxActions);
@@ -30,33 +31,37 @@ function setupActions() {
     messagesAdd: packets => reduxActions.messagesAdd(packets, idGenerator)
   };
 }
 
 /**
  * Prepare the store for use in testing.
  */
 function setupStore(input = [], {
-  storeOptions,
+  storeOptions = {},
   actions,
   hud,
 } = {}) {
   if (!hud) {
     hud = {
       proxy: {
         releaseActor: () => {},
         target: {
           activeTab: {
             ensureCSSErrorReportingEnabled: () => {}
           }
         },
       },
     };
   }
-  const store = configureStore(hud, storeOptions);
+  const store = configureStore(hud, {
+    ...storeOptions,
+    sessionId: -1,
+    telemetry: new Telemetry(),
+  });
 
   // Add the messages from the input commands to the store.
   const messagesAdd = actions
     ? actions.messagesAdd
     : reduxActions.messagesAdd;
   store.dispatch(messagesAdd(input.map(cmd => stubPackets.get(cmd))));
 
   return store;

--- a/devtools/client/webconsole/test/mocha-test-setup.js
+++ b/devtools/client/webconsole/test/mocha-test-setup.js
@@ -70,17 +70,19 @@ requireHacker.global_hook("default", (pa
       return `module.exports = require("devtools-modules/src/Services")`;
     case "devtools/shared/client/object-client":
     case "devtools/shared/client/long-string-client":
       return `() => {}`;
     case "devtools/client/netmonitor/src/components/TabboxPanel":
     case "devtools/client/webconsole/utils/context-menu":
       return "{}";
     case "devtools/client/shared/telemetry":
-      return `module.exports = function() {}`;
+      return `module.exports = function() {
+        this.recordEvent = () => {};
+      }`;
     case "devtools/shared/event-emitter":
       return `module.exports = require("devtools-modules/src/utils/event-emitter")`;
     case "devtools/client/shared/unicode-url":
       return `module.exports = require("devtools-modules/src/unicode-url")`;
   }
 
   // We need to rewrite all the modules assuming the root is mozilla-central and give them
   // an absolute path.

--- a/devtools/client/webconsole/test/mochitest/browser.ini
+++ b/devtools/client/webconsole/test/mochitest/browser.ini
@@ -357,16 +357,17 @@ skip-if = verify
 [browser_webconsole_split_close_button.js]
 [browser_webconsole_split_escape_key.js]
 [browser_webconsole_split_focus.js]
 [browser_webconsole_split_persist.js]
 [browser_webconsole_stacktrace_location_debugger_link.js]
 [browser_webconsole_stacktrace_location_scratchpad_link.js]
 [browser_webconsole_strict_mode_errors.js]
 [browser_webconsole_string.js]
+[browser_webconsole_telemetry_filters_changed.js]
 [browser_webconsole_time_methods.js]
 [browser_webconsole_timestamps.js]
 [browser_webconsole_trackingprotection_errors.js]
 tags = trackingprotection
 [browser_webconsole_view_source.js]
 [browser_webconsole_visibility_messages.js]
 [browser_webconsole_warn_about_replaced_api.js]
 [browser_webconsole_websocket.js]

new file mode 100644
--- /dev/null
+++ b/devtools/client/webconsole/test/mochitest/browser_webconsole_telemetry_filters_changed.js
@@ -0,0 +1,99 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Tests the filters_changed telemetry event.
+
+"use strict";
+
+const TEST_URI = `data:text/html,<meta charset=utf8><script>
+  console.log("test message");
+</script>`;
+
+const OPTOUT = Ci.nsITelemetry.DATASET_RELEASE_CHANNEL_OPTOUT;
+
+add_task(async function() {
+  // Let's reset the counts.
+  Services.telemetry.clearEvents();
+
+  // Ensure no events have been logged
+  const snapshot = Services.telemetry.snapshotEvents(OPTOUT, true);
+  ok(!snapshot.parent, "No events have been logged for the main process");
+
+  const hud = await openNewTabAndConsole(TEST_URI);
+
+  info("Click on the 'log' filter");
+  await setFilterState(hud, {
+    log: false
+  });
+
+  checkTelemetryEvent({
+    trigger: "log",
+    active: "error,warn,info,debug",
+    inactive: "text,log,css,net,netxhr",
+  });
+
+  info("Click on the 'netxhr' filter");
+  await setFilterState(hud, {
+    netxhr: true
+  });
+
+  checkTelemetryEvent({
+    trigger: "netxhr",
+    active: "error,warn,info,debug,netxhr",
+    inactive: "text,log,css,net",
+  });
+
+  info("Filter the output using the text filter input");
+  hud.ui.filterBox.focus();
+  hud.ui.filterBox.select();
+  EventUtils.sendString("no match");
+
+  checkTelemetryEvent({
+    trigger: "text",
+    active: "text,error,warn,info,debug,netxhr",
+    inactive: "log,css,net",
+  });
+
+  info("Clear the filters using the 'Reset filters' button");
+  const resetButton = await waitFor(() =>
+    hud.ui.window.document.querySelector(".reset-filters-button"));
+  const onResetButtonHidden = waitFor(() =>
+    !hud.ui.window.document.querySelector(".reset-filters-button"));
+  resetButton.click();
+  await onResetButtonHidden;
+
+  checkTelemetryEvent({
+    trigger: "reset",
+    active: "error,warn,log,info,debug,netxhr",
+    inactive: "text,css,net",
+  });
+});
+
+function checkTelemetryEvent(expectedEvent) {
+  const events = getFiltersChangedEventsExtra();
+  is(events.length, 1, "There was only 1 event logged");
+  const [event] = events;
+  ok(event.session_id > 0, "There is a valid session_id in the logged event");
+  const f = e => JSON.stringify(e, null, 2);
+  is(f(event), f({
+    ...expectedEvent,
+    "session_id": event.session_id
+  }), "The event has the expected data");
+}
+
+function getFiltersChangedEventsExtra() {
+  // Retrieve and clear telemetry events.
+  const snapshot = Services.telemetry.snapshotEvents(OPTOUT, true);
+
+  const filtersChangedEvents = snapshot.parent.filter(event =>
+    event[1] === "devtools.main" &&
+    event[2] === "filters_changed" &&
+    event[3] === "webconsole"
+  );
+
+  // Since we already know we have the correct event, we only return the `extra` field
+  // that was passed to it (which is event[5] here).
+  return filtersChangedEvents.map(event => event[5]);
+}

--- a/devtools/client/webconsole/webconsole-output-wrapper.js
+++ b/devtools/client/webconsole/webconsole-output-wrapper.js
@@ -32,17 +32,21 @@ function WebConsoleOutputWrapper(parentN
 
   this.queuedMessageAdds = [];
   this.queuedMessageUpdates = [];
   this.queuedRequestUpdates = [];
   this.throttledDispatchPromise = null;
 
   this.telemetry = new Telemetry();
 
-  store = configureStore(this.hud);
+  store = configureStore(this.hud, {
+    // We may not have access to the toolbox (e.g. in the browser console).
+    sessionId: this.toolbox && this.toolbox.sessionId || -1,
+    telemetry: this.telemetry,
+  });
 }
 
 WebConsoleOutputWrapper.prototype = {
   init: function() {
     return new Promise((resolve) => {
       const attachRefToHud = (id, node) => {
         this.hud[id] = node;
       };

--- a/devtools/server/actors/inspector/node.js
+++ b/devtools/server/actors/inspector/node.js
@@ -199,17 +199,18 @@ const NodeActor = protocol.ActorClassWit
     const hasSVGDocument = rawNode.getSVGDocument && rawNode.getSVGDocument();
     if (numChildren === 0 && (hasContentDocument || hasSVGDocument)) {
       // This might be an iframe with virtual children.
       numChildren = 1;
     }
 
     // Normal counting misses ::before/::after.  Also, some anonymous children
     // may ultimately be skipped, so we have to consult with the walker.
-    if (numChildren === 0 || hasAnonChildren || isShadowHost(this.rawNode)) {
+    if (numChildren === 0 || hasAnonChildren || isShadowHost(this.rawNode) ||
+      isShadowAnonymous(this.rawNode)) {
       numChildren = this.walker.countChildren(this);
     }
 
     return numChildren;
   },
 
   get computedStyle() {
     if (!this._computedStyle) {

--- a/devtools/server/main.js
+++ b/devtools/server/main.js
@@ -873,25 +873,27 @@ var DebuggerServer = {
       // Get messageManager from XUL browser (which might be a specialized tunnel for RDM)
       // or else fallback to asking the frameLoader itself.
       let mm = frame.messageManager || frame.frameLoader.messageManager;
       mm.loadFrameScript("resource://devtools/server/startup/frame.js", false);
 
       const trackMessageManager = () => {
         frame.addEventListener("DevTools:BrowserSwap", onBrowserSwap);
         mm.addMessageListener("debug:setup-in-parent", onSetupInParent);
+        mm.addMessageListener("debug:spawn-actor-in-parent", onSpawnActorInParent);
         if (!actor) {
           mm.addMessageListener("debug:actor", onActorCreated);
         }
         DebuggerServer._childMessageManagers.add(mm);
       };
 
       const untrackMessageManager = () => {
         frame.removeEventListener("DevTools:BrowserSwap", onBrowserSwap);
         mm.removeMessageListener("debug:setup-in-parent", onSetupInParent);
+        mm.removeMessageListener("debug:spawn-actor-in-parent", onSpawnActorInParent);
         if (!actor) {
           mm.removeMessageListener("debug:actor", onActorCreated);
         }
         DebuggerServer._childMessageManagers.delete(mm);
       };
 
       let actor, childTransport;
       const prefix = connection.allocID("child");
@@ -927,25 +929,74 @@ var DebuggerServer = {
             "Exception during actor module setup running in the parent process: ";
           DevToolsUtils.reportException(errorMessage + e);
           dumpn(`ERROR: ${errorMessage}\n\t module: '${module}'\n\t ` +
                 `setupParent: '${setupParent}'\n${DevToolsUtils.safeErrorString(e)}`);
           return false;
         }
       };
 
+      const onSpawnActorInParent = function(msg) {
+        // We may have multiple connectToFrame instance running for the same tab
+        // and need to filter the messages.
+        if (msg.json.prefix != connPrefix) {
+          return;
+        }
+
+        const { module, constructor, args, spawnedByActorID } = msg.json;
+        let m;
+
+        try {
+          m = require(module);
+
+          if (!(constructor in m)) {
+            dump(`ERROR: module '${module}' does not export '${constructor}'`);
+            return;
+          }
+
+          const Constructor = m[constructor];
+          // Bind the actor to parent process connection so that these actors
+          // directly communicates with the client as regular actors instanciated from
+          // parent process
+          const instance = new Constructor(connection, ...args, mm);
+          instance.conn = connection;
+          instance.parentID = spawnedByActorID;
+
+          // Manually set the actor ID in order to insert parent actorID as prefix
+          // in order to help identifying actor hiearchy via actor IDs.
+          // Remove `/` as it may confuse message forwarding between processes.
+          const contentPrefix = spawnedByActorID.replace(connection.prefix, "")
+                                                .replace("/", "-");
+          instance.actorID = connection.allocID(contentPrefix + "/" + instance.typeName);
+          connection.addActor(instance);
+
+          mm.sendAsyncMessage("debug:spawn-actor-in-parent:actor", {
+            prefix: connPrefix,
+            actorID: instance.actorID
+          });
+        } catch (e) {
+          const errorMessage =
+            "Exception during actor module setup running in the parent process: ";
+          DevToolsUtils.reportException(errorMessage + e + "\n" + e.stack);
+          dumpn(`ERROR: ${errorMessage}\n\t module: '${module}'\n\t ` +
+                `constructor: '${constructor}'\n${DevToolsUtils.safeErrorString(e)}`);
+        }
+      };
+
       const onActorCreated = DevToolsUtils.makeInfallible(function(msg) {
         if (msg.json.prefix != prefix) {
           return;
         }
         mm.removeMessageListener("debug:actor", onActorCreated);
 
         // Pipe Debugger message from/to parent/child via the message manager
         childTransport = new ChildDebuggerTransport(mm, prefix);
         childTransport.hooks = {
+          // Pipe all the messages from content process actors back to the client
+          // through the parent process connection.
           onPacket: connection.send.bind(connection),
           onClosed() {}
         };
         childTransport.ready();
 
         connection.setForwarding(prefix, childTransport);
 
         dumpn(`Start forwarding for frame with prefix ${prefix}`);
@@ -1335,16 +1386,17 @@ function DebuggerServerConnection(prefix
   /*
    * We can forward packets to other servers, if the actors on that server
    * all use a distinct prefix on their names. This is a map from prefixes
    * to transports: it maps a prefix P to a transport T if T conveys
    * packets to the server whose actors' names all begin with P + "/".
    */
   this._forwardingPrefixes = new Map();
 }
+exports.DebuggerServerConnection = DebuggerServerConnection;
 
 DebuggerServerConnection.prototype = {
   _prefix: null,
   get prefix() {
     return this._prefix;
   },
 
   _transport: null,
@@ -1804,9 +1856,54 @@ DebuggerServerConnection.prototype = {
     const { sendSyncMessage } = this.parentMessageManager;
 
     return sendSyncMessage("debug:setup-in-parent", {
       prefix: this.prefix,
       module: module,
       setupParent: setupParent
     });
   },
+
+  /**
+   * Instanciates a protocol.js actor in the parent process, from the content process
+   * module is the absolute path to protocol.js actor module
+   *
+   * @param spawnByActorID string
+   *        The actor ID of the actor that is requesting an actor to be created.
+   *        This is used as a prefix to compute the actor id of the actor created
+   *        in the parent process.
+   * @param module string
+   *        Absolute path for the actor module to load.
+   * @param constructor string
+   *        The symbol exported by this module that implements Actor.
+   * @param args array
+   *        Arguments to pass to its constructor
+   */
+  spawnActorInParentProcess(spawnedByActorID, { module, constructor, args }) {
+    if (!this.parentMessageManager) {
+      return null;
+    }
+
+    const { addMessageListener, removeMessageListener, sendAsyncMessage } =
+      this.parentMessageManager;
+
+    const onResponse = new Promise(done => {
+      const listener = msg => {
+        if (msg.json.prefix != this.prefix) {
+          return;
+        }
+        removeMessageListener("debug:spawn-actor-in-parent:actor", listener);
+        done(msg.json.actorID);
+      };
+      addMessageListener("debug:spawn-actor-in-parent:actor", listener);
+    });
+
+    sendAsyncMessage("debug:spawn-actor-in-parent", {
+      prefix: this.prefix,
+      module,
+      constructor,
+      args,
+      spawnedByActorID,
+    });
+
+    return onResponse;
+  }
 };