--- a/accessible/atk/DocAccessibleWrap.cpp
+++ b/accessible/atk/DocAccessibleWrap.cpp
@@ -9,18 +9,17 @@
 
 using namespace mozilla::a11y;
 
 ////////////////////////////////////////////////////////////////////////////////
 // DocAccessibleWrap
 ////////////////////////////////////////////////////////////////////////////////
 
 DocAccessibleWrap::
-  DocAccessibleWrap(nsIDocument* aDocument, nsIContent* aRootContent,
-                    nsIPresShell* aPresShell) :
-  DocAccessible(aDocument, aRootContent, aPresShell), mActivated(false)
+  DocAccessibleWrap(nsIDocument* aDocument, nsIPresShell* aPresShell) :
+  DocAccessible(aDocument, aPresShell), mActivated(false)
 {
 }
 
 DocAccessibleWrap::~DocAccessibleWrap()
 {
 }
 

--- a/accessible/atk/DocAccessibleWrap.h
+++ b/accessible/atk/DocAccessibleWrap.h
@@ -14,18 +14,17 @@
 #include "DocAccessible.h"
 
 namespace mozilla {
 namespace a11y {
 
 class DocAccessibleWrap : public DocAccessible
 {
 public:
-  DocAccessibleWrap(nsIDocument* aDocument, nsIContent* aRootContent,
-                    nsIPresShell* aPresShell);
+  DocAccessibleWrap(nsIDocument* aDocument, nsIPresShell* aPresShell);
   virtual ~DocAccessibleWrap();
 
   bool mActivated;
 };
 
 } // namespace a11y
 } // namespace mozilla
 

--- a/accessible/base/DocManager.cpp
+++ b/accessible/base/DocManager.cpp
@@ -465,27 +465,25 @@ DocManager::CreateDocOrRootAccessible(ns
     NS_ASSERTION(parentDocAcc,
                  "Can't create an accessible for the document!");
     if (!parentDocAcc)
       return nullptr;
   }
 
   // We only create root accessibles for the true root, otherwise create a
   // doc accessible.
-  nsIContent *rootElm = nsCoreUtils::GetRoleContent(aDocument);
   RefPtr<DocAccessible> docAcc = isRootDoc ?
-    new RootAccessibleWrap(aDocument, rootElm, presShell) :
-    new DocAccessibleWrap(aDocument, rootElm, presShell);
+    new RootAccessibleWrap(aDocument, presShell) :
+    new DocAccessibleWrap(aDocument, presShell);
 
   // Cache the document accessible into document cache.
   mDocAccessibleCache.Put(aDocument, docAcc);
 
   // Initialize the document accessible.
   docAcc->Init();
-  docAcc->SetRoleMapEntry(aria::GetRoleMap(aDocument));
 
   // Bind the document to the tree.
   if (isRootDoc) {
     if (!ApplicationAcc()->AppendChild(docAcc)) {
       docAcc->Shutdown();
       return nullptr;
     }
 

--- a/accessible/generic/DocAccessible.cpp
+++ b/accessible/generic/DocAccessible.cpp
@@ -71,19 +71,18 @@ static nsIAtom** kRelationAttrs[] =
 };
 
 static const uint32_t kRelationAttrsLen = ArrayLength(kRelationAttrs);
 
 ////////////////////////////////////////////////////////////////////////////////
 // Constructor/desctructor
 
 DocAccessible::
-  DocAccessible(nsIDocument* aDocument, nsIContent* aRootContent,
-                  nsIPresShell* aPresShell) :
-  HyperTextAccessibleWrap(aRootContent, this),
+  DocAccessible(nsIDocument* aDocument, nsIPresShell* aPresShell) :
+  HyperTextAccessibleWrap(nullptr, this),
   // XXX aaronl should we use an algorithm for the initial cache size?
   mAccessibleCache(kDefaultCacheLength),
   mNodeToAccessibleMap(kDefaultCacheLength),
   mDocumentNode(aDocument),
   mScrollPositionChangedTicks(0),
   mLoadState(eTreeConstructionPending), mDocFlags(0), mLoadEventType(0),
   mVirtualCursor(nullptr),
   mPresShell(aPresShell), mIPCDoc(nullptr)
@@ -1460,17 +1459,17 @@ DocAccessible::DoInitialUpdate()
     mDocFlags |= eTabDocument;
 
   mLoadState |= eTreeConstructed;
 
   // The content element may be changed before the initial update and then we
   // miss the notification (since content tree change notifications are ignored
   // prior to initial update). Make sure the content element is valid.
   nsIContent* contentElm = nsCoreUtils::GetRoleContent(mDocumentNode);
-  if (mContent != contentElm) {
+  if (contentElm) {
     mContent = contentElm;
     SetRoleMapEntry(aria::GetRoleMap(mContent));
   }
 
   // Build initial tree.  Since its the initial tree there's no group info to
   // invalidate.
   AutoTreeMutation mut(this, false);
   CacheChildrenInSubtree(this);

--- a/accessible/generic/DocAccessible.h
+++ b/accessible/generic/DocAccessible.h
@@ -45,18 +45,17 @@ class DocAccessible : public HyperTextAc
   NS_DECL_ISUPPORTS_INHERITED
   NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(DocAccessible, Accessible)
 
   NS_DECL_NSIOBSERVER
   NS_DECL_NSIACCESSIBLEPIVOTOBSERVER
 
 public:
 
-  DocAccessible(nsIDocument* aDocument, nsIContent* aRootContent,
-                nsIPresShell* aPresShell);
+  DocAccessible(nsIDocument* aDocument, nsIPresShell* aPresShell);
 
   // nsIScrollPositionListener
   virtual void ScrollPositionWillChange(nscoord aX, nscoord aY) override {}
   virtual void ScrollPositionDidChange(nscoord aX, nscoord aY) override;
 
   // nsIDocumentObserver
   NS_DECL_NSIDOCUMENTOBSERVER
 

--- a/accessible/generic/RootAccessible.cpp
+++ b/accessible/generic/RootAccessible.cpp
@@ -54,19 +54,18 @@ using namespace mozilla::dom;
 // nsISupports
 
 NS_IMPL_ISUPPORTS_INHERITED0(RootAccessible, DocAccessible)
 
 ////////////////////////////////////////////////////////////////////////////////
 // Constructor/destructor
 
 RootAccessible::
-  RootAccessible(nsIDocument* aDocument, nsIContent* aRootContent,
-                 nsIPresShell* aPresShell) :
-  DocAccessibleWrap(aDocument, aRootContent, aPresShell)
+  RootAccessible(nsIDocument* aDocument, nsIPresShell* aPresShell) :
+  DocAccessibleWrap(aDocument, aPresShell)
 {
   mType = eRootType;
 }
 
 RootAccessible::~RootAccessible()
 {
 }
 

--- a/accessible/generic/RootAccessible.h
+++ b/accessible/generic/RootAccessible.h
@@ -17,18 +17,17 @@ namespace mozilla {
 namespace a11y {
 
 class RootAccessible : public DocAccessibleWrap,
                        public nsIDOMEventListener
 {
   NS_DECL_ISUPPORTS_INHERITED
 
 public:
-  RootAccessible(nsIDocument* aDocument, nsIContent* aRootContent,
-                 nsIPresShell* aPresShell);
+  RootAccessible(nsIDocument* aDocument, nsIPresShell* aPresShell);
 
   // nsIDOMEventListener
   NS_IMETHOD HandleEvent(nsIDOMEvent* aEvent) override;
 
   // Accessible
   virtual void Shutdown() override;
   virtual mozilla::a11y::ENameValueFlag Name(nsString& aName) override;
   virtual Relation RelationByType(RelationType aType) override;

--- a/accessible/jsat/AccessFu.jsm
+++ b/accessible/jsat/AccessFu.jsm
@@ -339,17 +339,17 @@ this.AccessFu = { // jshint ignore:line
       case 'Accessibility:MoveByGranularity':
         this.Input.moveByGranularity(JSON.parse(aData));
         break;
       case 'remote-browser-shown':
       case 'inprocess-browser-shown':
       {
         // Ignore notifications that aren't from a BrowserOrApp
         let frameLoader = aSubject.QueryInterface(Ci.nsIFrameLoader);
-        if (!frameLoader.ownerIsBrowserOrAppFrame) {
+        if (!frameLoader.ownerIsMozBrowserOrAppFrame) {
           return;
         }
         this._handleMessageManager(frameLoader.messageManager);
         break;
       }
     }
   },
 

--- a/accessible/mac/DocAccessibleWrap.h
+++ b/accessible/mac/DocAccessibleWrap.h
@@ -9,18 +9,17 @@
 #include "DocAccessible.h"
 
 namespace mozilla {
 namespace a11y {
 
 class DocAccessibleWrap : public DocAccessible
 {
 public:
-  DocAccessibleWrap(nsIDocument* aDocument, nsIContent* aRootContent,
-                    nsIPresShell* aPresShell);
+  DocAccessibleWrap(nsIDocument* aDocument, nsIPresShell* aPresShell);
   virtual ~DocAccessibleWrap();
 
 };
 
 } // namespace a11y
 } // namespace mozilla
 
 #endif

--- a/accessible/mac/DocAccessibleWrap.mm
+++ b/accessible/mac/DocAccessibleWrap.mm
@@ -5,18 +5,17 @@
 
 #include "DocAccessibleWrap.h"
 
 #import "mozAccessible.h"
 
 using namespace mozilla::a11y;
 
 DocAccessibleWrap::
-  DocAccessibleWrap(nsIDocument* aDocument, nsIContent* aRootContent,
-                    nsIPresShell* aPresShell) :
-  DocAccessible(aDocument, aRootContent, aPresShell)
+  DocAccessibleWrap(nsIDocument* aDocument, nsIPresShell* aPresShell) :
+  DocAccessible(aDocument, aPresShell)
 {
 }
 
 DocAccessibleWrap::~DocAccessibleWrap()
 {
 }
 

--- a/accessible/mac/RootAccessibleWrap.h
+++ b/accessible/mac/RootAccessibleWrap.h
@@ -13,18 +13,17 @@
 #include "RootAccessible.h"
 
 namespace mozilla {
 namespace a11y {
 
 class RootAccessibleWrap : public RootAccessible
 {
 public:
-  RootAccessibleWrap(nsIDocument* aDocument, nsIContent* aRootContent,
-                     nsIPresShell* aPresShell);
+  RootAccessibleWrap(nsIDocument* aDocument, nsIPresShell* aPresShell);
   virtual ~RootAccessibleWrap();
 
     Class GetNativeType ();
 
     // let's our native accessible get in touch with the
     // native cocoa view that is our accessible parent.
     void GetNativeWidget (void **aOutView);
 };

--- a/accessible/mac/RootAccessibleWrap.mm
+++ b/accessible/mac/RootAccessibleWrap.mm
@@ -11,19 +11,18 @@
 #include "nsObjCExceptions.h"
 #include "nsIFrame.h"
 #include "nsView.h"
 #include "nsIWidget.h"
 
 using namespace mozilla::a11y;
 
 RootAccessibleWrap::
-  RootAccessibleWrap(nsIDocument* aDocument, nsIContent* aRootContent,
-                     nsIPresShell* aPresShell) :
-  RootAccessible(aDocument, aRootContent, aPresShell)
+  RootAccessibleWrap(nsIDocument* aDocument, nsIPresShell* aPresShell) :
+  RootAccessible(aDocument, aPresShell)
 {
 }
 
 RootAccessibleWrap::~RootAccessibleWrap()
 {
 }
 
 Class

--- a/accessible/tests/mochitest/events/test_valuechange.html
+++ b/accessible/tests/mochitest/events/test_valuechange.html
@@ -15,18 +15,16 @@
           src="../common.js"></script>
   <script type="application/javascript"
           src="../events.js"></script>
 
   <script type="application/javascript"
           src="../value.js"></script>
 
   <script type="application/javascript">
-
-
     /**
      * Do tests.
      */
     var gQueue = null;
 
     // Value change invoker
     function changeARIAValue(aNodeOrID, aValuenow, aValuetext)
     {
@@ -127,16 +125,39 @@
       }
 
       this.getID = function changeRangeValue_getID()
       {
         return prettyName(aID) + " range value changed";
       }
     }
 
+    function changeSelectValue(aID, aKey, aValue)
+    {
+      this.eventSeq = [new invokerChecker(EVENT_TEXT_VALUE_CHANGE, aID)];
+
+      this.invoke = function changeSelectValue_invoke()
+      {
+        getNode(aID).focus();
+        synthesizeKey(aKey, {}, window);
+      }
+
+      this.finalCheck = function changeSelectValue_finalCheck()
+      {
+        is(getAccessible(aID).value, aValue, "Wrong value for " + prettyName(aID));
+      }
+
+      this.getID = function changeSelectValue_getID()
+      {
+        return `${prettyName(aID)} closed select value change on '${aKey}'' key press`;
+      }
+    }
+
+    //enableLogging("DOMEvents");
+    //gA11yEventDumpToConsole = true;
     function doTests()
     {
       // Test initial values
       testValue("slider_vn", "5", 5, 0, 1000, 0);
       testValue("slider_vnvt", "plain", 0, 0, 5, 0);
       testValue("slider_vt", "hi", 0, 0, 3, 0);
       testValue("scrollbar", "5", 5, 0, 1000, 0);
       testValue("progress", "22%", 22, 0, 100, 0);
@@ -150,16 +171,19 @@
       gQueue.push(new changeARIAValue("slider_vnvt", "3", "sweet"));
       gQueue.push(new changeARIAValue("scrollbar", "6", undefined));
 
       gQueue.push(new changeValue("combobox", "hello"));
 
       gQueue.push(new changeProgressValue("progress", "50"));
       gQueue.push(new changeRangeValue("range"));
 
+      gQueue.push(new changeSelectValue("select", "VK_DOWN", "2nd"));
+      gQueue.push(new changeSelectValue("select", "3", "3rd"));
+
       gQueue.invoke(); // Will call SimpleTest.finish();
     }
 
     SimpleTest.waitForExplicitFinish();
     addA11yLoadEvent(doTests);
   </script>
 </head>
 
@@ -216,10 +240,15 @@
   <input id="combobox" role="combobox" aria-autocomplete="inline">
 
   <!-- progress bar -->
   <progress id="progress" value="22" max="100"></progress>
 
   <!-- input@type="range" -->
   <input type="range" id="range" min="0" max="10" value="6">
 
+  <select id="select">
+    <option>1st</option>
+    <option>2nd</option>
+    <option>3rd</option>
+  </select>
 </body>
 </html>

--- a/accessible/windows/msaa/DocAccessibleWrap.cpp
+++ b/accessible/windows/msaa/DocAccessibleWrap.cpp
@@ -20,19 +20,18 @@
 using namespace mozilla;
 using namespace mozilla::a11y;
 
 ////////////////////////////////////////////////////////////////////////////////
 // DocAccessibleWrap
 ////////////////////////////////////////////////////////////////////////////////
 
 DocAccessibleWrap::
-  DocAccessibleWrap(nsIDocument* aDocument, nsIContent* aRootContent,
-                    nsIPresShell* aPresShell) :
-  DocAccessible(aDocument, aRootContent, aPresShell), mHWND(nullptr)
+  DocAccessibleWrap(nsIDocument* aDocument, nsIPresShell* aPresShell) :
+  DocAccessible(aDocument, aPresShell), mHWND(nullptr)
 {
 }
 
 DocAccessibleWrap::~DocAccessibleWrap()
 {
 }
 
 IMPL_IUNKNOWN_QUERY_HEAD(DocAccessibleWrap)

--- a/accessible/windows/msaa/DocAccessibleWrap.h
+++ b/accessible/windows/msaa/DocAccessibleWrap.h
@@ -10,18 +10,17 @@
 #include "DocAccessible.h"
 
 namespace mozilla {
 namespace a11y {
 
 class DocAccessibleWrap : public DocAccessible
 {
 public:
-  DocAccessibleWrap(nsIDocument* aDocument, nsIContent* aRootContent,
-                    nsIPresShell* aPresShell);
+  DocAccessibleWrap(nsIDocument* aDocument, nsIPresShell* aPresShell);
   virtual ~DocAccessibleWrap();
 
   DECL_IUNKNOWN_INHERITED
 
   // IAccessible
 
     // Override get_accValue to provide URL when no other value is available
     virtual /* [id][propget] */ HRESULT STDMETHODCALLTYPE get_accValue( 

--- a/accessible/windows/msaa/RootAccessibleWrap.cpp
+++ b/accessible/windows/msaa/RootAccessibleWrap.cpp
@@ -10,19 +10,18 @@
 #include "nsWinUtils.h"
 
 using namespace mozilla::a11y;
 
 ////////////////////////////////////////////////////////////////////////////////
 // Constructor/desctructor
 
 RootAccessibleWrap::
-  RootAccessibleWrap(nsIDocument* aDocument, nsIContent* aRootContent,
-                     nsIPresShell* aPresShell) :
-  RootAccessible(aDocument, aRootContent, aPresShell)
+  RootAccessibleWrap(nsIDocument* aDocument, nsIPresShell* aPresShell) :
+  RootAccessible(aDocument, aPresShell)
 {
 }
 
 RootAccessibleWrap::~RootAccessibleWrap()
 {
 }
 
 ////////////////////////////////////////////////////////////////////////////////

--- a/accessible/windows/msaa/RootAccessibleWrap.h
+++ b/accessible/windows/msaa/RootAccessibleWrap.h
@@ -9,18 +9,17 @@
 #include "RootAccessible.h"
 
 namespace mozilla {
 namespace a11y {
 
 class RootAccessibleWrap : public RootAccessible
 {
 public:
-  RootAccessibleWrap(nsIDocument* aDocument, nsIContent* aRootContent,
-                     nsIPresShell* aPresShell);
+  RootAccessibleWrap(nsIDocument* aDocument, nsIPresShell* aPresShell);
   virtual ~RootAccessibleWrap();
 
   // RootAccessible
   virtual void DocumentActivated(DocAccessible* aDocument);
 };
 
 } // namespace a11y
 } // namespace mozilla

--- a/addon-sdk/source/lib/sdk/context-menu.js
+++ b/addon-sdk/source/lib/sdk/context-menu.js
@@ -62,18 +62,19 @@ const OVERFLOW_POPUP_CLASS = "addon-cont
 
 // Holds private properties for API objects
 var internal = ns();
 
 // A little hacky but this is the last process ID that last opened the context
 // menu
 var lastContextProcessId = null;
 
+var uuidModule = require('./util/uuid');
 function uuid() {
-  return require('./util/uuid').uuid().toString();
+  return uuidModule.uuid().toString();
 }
 
 function getScheme(spec) {
   try {
     return URL(spec).scheme;
   }
   catch(e) {
     return null;

--- a/b2g/chrome/content/runapp.js
+++ b/b2g/chrome/content/runapp.js
@@ -52,17 +52,17 @@ function AppRunner(aName) {
   this._apps = [];
 }
 AppRunner.prototype = {
   observe: function(aSubject, aTopic, aData) {
     let frameLoader = aSubject;
     // get a ref to the app <iframe>
     frameLoader.QueryInterface(Ci.nsIFrameLoader);
     // Ignore notifications that aren't from a BrowserOrApp
-    if (!frameLoader.ownerIsBrowserOrAppFrame) {
+    if (!frameLoader.ownerIsMozBrowserOrAppFrame) {
       return;
     }
 
     let frame = frameLoader.ownerElement;
     if (!frame.appManifestURL) { // Ignore all frames but app frames
       return;
     }
 

--- a/b2g/components/AboutServiceWorkers.jsm
+++ b/b2g/components/AboutServiceWorkers.jsm
@@ -139,17 +139,17 @@ this.AboutServiceWorkers = {
         self.sendResult(message.id, true);
         break;
 
       case "unregister":
         if (!message.principal ||
             !message.principal.origin ||
             !message.principal.originAttributes ||
             !message.principal.originAttributes.appId ||
-            (message.principal.originAttributes.inBrowser == null)) {
+            (message.principal.originAttributes.inIsolatedMozBrowser == null)) {
           self.sendError(message.id, "MissingPrincipal");
           return;
         }
 
         let principal = Services.scriptSecurityManager.createCodebasePrincipal(
           // TODO: Bug 1196652. use originNoSuffix
           Services.io.newURI(message.principal.origin, null, null),
           message.principal.originAttributes);

--- a/b2g/components/ErrorPage.jsm
+++ b/b2g/components/ErrorPage.jsm
@@ -172,16 +172,16 @@ var ErrorPage = {
   init: function errorPageInit() {
     Services.obs.addObserver(this, 'inprocess-browser-shown', false);
     Services.obs.addObserver(this, 'remote-browser-shown', false);
   },
 
   observe: function errorPageObserve(aSubject, aTopic, aData) {
     let frameLoader = aSubject.QueryInterface(Ci.nsIFrameLoader);
     // Ignore notifications that aren't from a BrowserOrApp
-    if (!frameLoader.ownerIsBrowserOrAppFrame) {
+    if (!frameLoader.ownerIsMozBrowserOrAppFrame) {
       return;
     }
     this._listenError(frameLoader);
   }
 };
 
 ErrorPage.init();

--- a/browser/app/profile/firefox.js
+++ b/browser/app/profile/firefox.js
@@ -1372,16 +1372,19 @@ pref("browser.newtabpage.columns", 5);
 pref("browser.newtabpage.directory.source", "https://tiles.services.mozilla.com/v3/links/fetch/%LOCALE%/%CHANNEL%");
 
 // endpoint to send newtab click and view pings
 pref("browser.newtabpage.directory.ping", "https://tiles.services.mozilla.com/v3/links/");
 
 // activates the remote-hosted newtab page
 pref("browser.newtabpage.remote", false);
 
+// Toggles endpoints allowed for remote newtab communications
+pref("browser.newtabpage.remote.mode", "production");
+
 // Enable the DOM fullscreen API.
 pref("full-screen-api.enabled", true);
 
 // Startup Crash Tracking
 // number of startup crashes that can occur before starting into safe mode automatically
 // (this pref has no effect if more than 6 hours have passed since the last crash)
 pref("toolkit.startup.max_resumed_crashes", 3);
 
@@ -1650,8 +1653,11 @@ pref("toolkit.pageThumbs.minHeight", 190
 #ifdef NIGHTLY_BUILD
 // Enable speech synthesis, only Nightly for now
 pref("media.webspeech.synth.enabled", true);
 #endif
 
 pref("browser.esedbreader.loglevel", "Error");
 
 pref("browser.laterrun.enabled", false);
+
+// Enable browser frames for use on desktop.  Only exposed to chrome callers.
+pref("dom.mozBrowserFramesEnabled", true);

--- a/browser/components/newtab/NewTabPrefsProvider.jsm
+++ b/browser/components/newtab/NewTabPrefsProvider.jsm
@@ -13,16 +13,17 @@ Cu.import("resource://gre/modules/XPCOMU
 XPCOMUtils.defineLazyGetter(this, "EventEmitter", function() {
   const {EventEmitter} = Cu.import("resource://devtools/shared/event-emitter.js", {});
   return EventEmitter;
 });
 
 // Supported prefs and data type
 const gPrefsMap = new Map([
   ["browser.newtabpage.remote", "bool"],
+  ["browser.newtabpage.remote.mode", "str"],
   ["browser.newtabpage.enabled", "bool"],
   ["browser.newtabpage.enhanced", "bool"],
   ["browser.newtabpage.pinned", "str"],
   ["intl.locale.matchOS", "bool"],
   ["general.useragent.locale", "localized"],
 ]);
 
 let PrefsProvider = function PrefsProvider() {

new file mode 100644
--- /dev/null
+++ b/browser/components/newtab/NewTabRemoteResources.jsm
@@ -0,0 +1,13 @@
+/* exported MODE_CHANNEL_MAP */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = ["MODE_CHANNEL_MAP"];
+
+const MODE_CHANNEL_MAP = {
+  "production": {origin: "https://content.cdn.mozilla.net"},
+  "staging": {origin: "https://content-cdn.stage.mozaws.net"},
+  "test": {origin: "https://example.com"},
+  "test2": {origin: "http://mochi.test:8888"},
+  "dev": {origin: "http://localhost:8888"}
+};

--- a/browser/components/newtab/aboutNewTabService.js
+++ b/browser/components/newtab/aboutNewTabService.js
@@ -1,54 +1,60 @@
 /*
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */
 
 /* globals XPCOMUtils, NewTabPrefsProvider, Services,
-  Locale, UpdateUtils
+  Locale, UpdateUtils, MODE_CHANNEL_MAP
 */
 "use strict";
 
 const {utils: Cu, interfaces: Ci} = Components;
 
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://gre/modules/Services.jsm");
 
 XPCOMUtils.defineLazyModuleGetter(this, "UpdateUtils",
                                   "resource://gre/modules/UpdateUtils.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "NewTabPrefsProvider",
                                   "resource:///modules/NewTabPrefsProvider.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "Locale",
                                   "resource://gre/modules/Locale.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "MODE_CHANNEL_MAP",
+                                  "resource:///modules/NewTabRemoteResources.jsm");
 
 const LOCAL_NEWTAB_URL = "chrome://browser/content/newtab/newTab.xhtml";
 
-const REMOTE_NEWTAB_URL = "https://newtab.cdn.mozilla.net/" +
-                              "v%VERSION%/%CHANNEL%/%LOCALE%/index.html";
+const REMOTE_NEWTAB_PATH = "/v%VERSION%/%CHANNEL%/%LOCALE%/index.html";
 
 const ABOUT_URL = "about:newtab";
 
 // Pref that tells if remote newtab is enabled
 const PREF_REMOTE_ENABLED = "browser.newtabpage.remote";
 
 // The preference that tells whether to match the OS locale
 const PREF_MATCH_OS_LOCALE = "intl.locale.matchOS";
 
 // The preference that tells what locale the user selected
 const PREF_SELECTED_LOCALE = "general.useragent.locale";
 
+// The preference that tells what remote mode is enabled.
+const PREF_REMOTE_MODE = "browser.newtabpage.remote.mode";
+
 const VALID_CHANNELS = new Set(["esr", "release", "beta", "aurora", "nightly"]);
 
 const REMOTE_NEWTAB_VERSION = "0";
 
 function AboutNewTabService() {
   NewTabPrefsProvider.prefs.on(PREF_REMOTE_ENABLED, this._handleToggleEvent.bind(this));
 
+  this._updateRemoteMaybe = this._updateRemoteMaybe.bind(this);
+
   // trigger remote change if needed, according to pref
   this.toggleRemote(Services.prefs.getBoolPref(PREF_REMOTE_ENABLED));
 }
 
 /*
  * A service that allows for the overriding, at runtime, of the newtab page's url.
  * Additionally, the service manages pref state between a remote and local newtab page.
  *
@@ -119,40 +125,48 @@ AboutNewTabService.prototype = {
       // exit there is no change of state
       return false;
     }
 
     if (stateEnabled) {
       this._remoteURL = this.generateRemoteURL();
       NewTabPrefsProvider.prefs.on(
         PREF_SELECTED_LOCALE,
-        this._updateRemoteMaybe.bind(this));
+        this._updateRemoteMaybe);
       NewTabPrefsProvider.prefs.on(
         PREF_MATCH_OS_LOCALE,
-        this._updateRemoteMaybe.bind(this));
+        this._updateRemoteMaybe);
+      NewTabPrefsProvider.prefs.on(
+        PREF_REMOTE_MODE,
+        this._updateRemoteMaybe);
       this._remoteEnabled = true;
     } else {
       NewTabPrefsProvider.prefs.off(PREF_SELECTED_LOCALE, this._updateRemoteMaybe);
       NewTabPrefsProvider.prefs.off(PREF_MATCH_OS_LOCALE, this._updateRemoteMaybe);
+      NewTabPrefsProvider.prefs.off(PREF_REMOTE_MODE, this._updateRemoteMaybe);
       this._remoteEnabled = false;
     }
     this._newTabURL = ABOUT_URL;
     return true;
   },
 
   /*
-   * Generate a default url based on locale and update channel
+   * Generate a default url based on remote mode, version, locale and update channel
    */
   generateRemoteURL() {
     let releaseName = this.releaseFromUpdateChannel(UpdateUtils.UpdateChannel);
-    let url = REMOTE_NEWTAB_URL
+    let path = REMOTE_NEWTAB_PATH
       .replace("%VERSION%", REMOTE_NEWTAB_VERSION)
       .replace("%LOCALE%", Locale.getLocale())
       .replace("%CHANNEL%", releaseName);
-    return url;
+    let mode = Services.prefs.getCharPref(PREF_REMOTE_MODE, "production");
+    if (!(mode in MODE_CHANNEL_MAP)) {
+      mode = "production";
+    }
+    return MODE_CHANNEL_MAP[mode].origin + path;
   },
 
   /*
    * Returns the default URL.
    *
    * This URL only depends on the browser.newtabpage.remote pref. Overriding
    * the newtab page has no effect on the result of this function.
    *

--- a/browser/components/newtab/moz.build
+++ b/browser/components/newtab/moz.build
@@ -7,16 +7,17 @@
 BROWSER_CHROME_MANIFESTS += ['tests/browser/browser.ini']
 
 XPCSHELL_TESTS_MANIFESTS += [
     'tests/xpcshell/xpcshell.ini',
 ]
 
 EXTRA_JS_MODULES += [
     'NewTabPrefsProvider.jsm',
+    'NewTabRemoteResources.jsm',
     'NewTabURL.jsm',
     'PlacesProvider.jsm'
 ]
 
 XPIDL_SOURCES += [
     'nsIAboutNewTabService.idl',
 ]
 

--- a/browser/components/newtab/tests/xpcshell/test_AboutNewTabService.js
+++ b/browser/components/newtab/tests/xpcshell/test_AboutNewTabService.js
@@ -100,35 +100,50 @@ add_task(function* test_override_remote_
 add_task(function* test_updates() {
   /*
    * Simulates a "cold-boot" situation, with some pref already set before testing a series
    * of changes.
    */
   Preferences.set("browser.newtabpage.remote", true);
   aboutNewTabService.resetNewTabURL(); // need to set manually because pref notifs are off
   let notificationPromise;
-  let expectedHref = "https://newtab.cdn.mozilla.net" +
-                     `/v${aboutNewTabService.remoteVersion}` +
+  let productionModeBaseUrl = "https://content.cdn.mozilla.net";
+  let testModeBaseUrl = "https://example.com";
+  let expectedPath = `/v${aboutNewTabService.remoteVersion}` +
                      `/${aboutNewTabService.remoteReleaseName}` +
                      "/en-GB" +
                      "/index.html";
+  let expectedHref = productionModeBaseUrl + expectedPath;
   Preferences.set("intl.locale.matchOS", true);
   Preferences.set("general.useragent.locale", "en-GB");
+  Preferences.set("browser.newtabpage.remote.mode", "production");
   NewTabPrefsProvider.prefs.init();
 
   // test update checks for prefs
   notificationPromise = nextChangeNotificationPromise(
     expectedHref, "Remote href should be updated");
   Preferences.set("intl.locale.matchOS", false);
   yield notificationPromise;
 
   notificationPromise = nextChangeNotificationPromise(
     DEFAULT_HREF, "Remote href changes back to default");
   Preferences.set("general.useragent.locale", "en-US");
+  yield notificationPromise;
 
+  // test update fires when mode is changed
+  expectedPath = expectedPath.replace("/en-GB/", "/en-US/");
+  notificationPromise = nextChangeNotificationPromise(
+    testModeBaseUrl + expectedPath, "Remote href changes back to origin of test mode");
+  Preferences.set("browser.newtabpage.remote.mode", "test");
+  yield notificationPromise;
+
+  // test invalid mode ends up pointing to production url
+  notificationPromise = nextChangeNotificationPromise(
+    DEFAULT_HREF, "Remote href changes back to production default");
+  Preferences.set("browser.newtabpage.remote.mode", "invalid");
   yield notificationPromise;
 
   // test update fires on override and reset
   let testURL = "https://example.com/";
   notificationPromise = nextChangeNotificationPromise(
     testURL, "a notification occurs on override");
   aboutNewTabService.newTabURL = testURL;
   yield notificationPromise;

--- a/browser/components/sessionstore/SessionHistory.jsm
+++ b/browser/components/sessionstore/SessionHistory.jsm
@@ -140,16 +140,20 @@ var SessionHistoryInternal = {
       entry.referrer = shEntry.referrerURI.spec;
       entry.referrerPolicy = shEntry.referrerPolicy;
     }
 
     if (shEntry.originalURI) {
       entry.originalURI = shEntry.originalURI.spec;
     }
 
+    if (shEntry.loadReplace) {
+      entry.loadReplace = shEntry.loadReplace;
+    }
+
     if (shEntry.srcdocData)
       entry.srcdocData = shEntry.srcdocData;
 
     if (shEntry.isSrcdocEntry)
       entry.isSrcdocEntry = shEntry.isSrcdocEntry;
 
     if (shEntry.baseURI)
       entry.baseURI = shEntry.baseURI.spec;
@@ -311,16 +315,19 @@ var SessionHistoryInternal = {
       shEntry.contentType = entry.contentType;
     if (entry.referrer) {
       shEntry.referrerURI = Utils.makeURI(entry.referrer);
       shEntry.referrerPolicy = entry.referrerPolicy;
     }
     if (entry.originalURI) {
       shEntry.originalURI = Utils.makeURI(entry.originalURI);
     }
+    if (entry.loadReplace) {
+      shEntry.loadReplace = entry.loadReplace;
+    }
     if (entry.isSrcdocEntry)
       shEntry.srcdocData = entry.srcdocData;
     if (entry.baseURI)
       shEntry.baseURI = Utils.makeURI(entry.baseURI);
 
     if (entry.cacheKey) {
       var cacheKey = Cc["@mozilla.org/supports-PRUint32;1"].
                      createInstance(Ci.nsISupportsPRUint32);

--- a/caps/BasePrincipal.cpp
+++ b/caps/BasePrincipal.cpp
@@ -31,72 +31,72 @@ namespace mozilla {
 
 using dom::URLParams;
 
 void
 PrincipalOriginAttributes::InheritFromDocShellToDoc(const DocShellOriginAttributes& aAttrs,
                                                     const nsIURI* aURI)
 {
   mAppId = aAttrs.mAppId;
-  mInBrowser = aAttrs.mInBrowser;
+  mInIsolatedMozBrowser = aAttrs.mInIsolatedMozBrowser;
 
   // addonId is computed from the principal URI and never propagated
   mUserContextId = aAttrs.mUserContextId;
 
   // TODO:
   // Bug 1225349 - PrincipalOriginAttributes should inherit mSignedPkg
   // accordingly by URI
   mSignedPkg = aAttrs.mSignedPkg;
 }
 
 void
 PrincipalOriginAttributes::InheritFromNecko(const NeckoOriginAttributes& aAttrs)
 {
   mAppId = aAttrs.mAppId;
-  mInBrowser = aAttrs.mInBrowser;
+  mInIsolatedMozBrowser = aAttrs.mInIsolatedMozBrowser;
 
   // addonId is computed from the principal URI and never propagated
   mUserContextId = aAttrs.mUserContextId;
   mSignedPkg = aAttrs.mSignedPkg;
 }
 
 void
 DocShellOriginAttributes::InheritFromDocToChildDocShell(const PrincipalOriginAttributes& aAttrs)
 {
   mAppId = aAttrs.mAppId;
-  mInBrowser = aAttrs.mInBrowser;
+  mInIsolatedMozBrowser = aAttrs.mInIsolatedMozBrowser;
 
   // addonId is computed from the principal URI and never propagated
   mUserContextId = aAttrs.mUserContextId;
 
   // TODO:
   // Bug 1225353 - DocShell/NeckoOriginAttributes should inherit
   // mSignedPkg accordingly by mSignedPkgInBrowser
   mSignedPkg = aAttrs.mSignedPkg;
 }
 
 void
 NeckoOriginAttributes::InheritFromDocToNecko(const PrincipalOriginAttributes& aAttrs)
 {
   mAppId = aAttrs.mAppId;
-  mInBrowser = aAttrs.mInBrowser;
+  mInIsolatedMozBrowser = aAttrs.mInIsolatedMozBrowser;
 
   // addonId is computed from the principal URI and never propagated
   mUserContextId = aAttrs.mUserContextId;
 
   // TODO:
   // Bug 1225353 - DocShell/NeckoOriginAttributes should inherit
   // mSignedPkg accordingly by mSignedPkgInBrowser
 }
 
 void
 NeckoOriginAttributes::InheritFromDocShellToNecko(const DocShellOriginAttributes& aAttrs)
 {
   mAppId = aAttrs.mAppId;
-  mInBrowser = aAttrs.mInBrowser;
+  mInIsolatedMozBrowser = aAttrs.mInIsolatedMozBrowser;
 
   // addonId is computed from the principal URI and never propagated
   mUserContextId = aAttrs.mUserContextId;
 
   // TODO:
   // Bug 1225353 - DocShell/NeckoOriginAttributes should inherit
   // mSignedPkg accordingly by mSignedPkgInBrowser
 }
@@ -114,17 +114,17 @@ OriginAttributes::CreateSuffix(nsACStrin
   // naming (see addonId below).
   //
 
   if (mAppId != nsIScriptSecurityManager::NO_APP_ID) {
     value.AppendInt(mAppId);
     params->Set(NS_LITERAL_STRING("appId"), value);
   }
 
-  if (mInBrowser) {
+  if (mInIsolatedMozBrowser) {
     params->Set(NS_LITERAL_STRING("inBrowser"), NS_LITERAL_STRING("1"));
   }
 
   if (!mAddonId.IsEmpty()) {
     if (mAddonId.FindCharInSet(dom::quota::QuotaManager::kReplaceChars) != kNotFound) {
 #ifdef MOZ_CRASHREPORTER
       CrashReporter::AnnotateCrashReport(NS_LITERAL_CSTRING("Crash_AddonId"),
                                          NS_ConvertUTF16toUTF8(mAddonId));
@@ -186,17 +186,17 @@ public:
       return true;
     }
 
     if (aName.EqualsLiteral("inBrowser")) {
       if (!aValue.EqualsLiteral("1")) {
         return false;
       }
 
-      mOriginAttributes->mInBrowser = true;
+      mOriginAttributes->mInIsolatedMozBrowser = true;
       return true;
     }
 
     if (aName.EqualsLiteral("addonId")) {
       MOZ_RELEASE_ASSERT(mOriginAttributes->mAddonId.IsEmpty());
       mOriginAttributes->mAddonId.Assign(aValue);
       return true;
     }
@@ -464,17 +464,17 @@ BasePrincipal::GetIsSystemPrincipal(bool
 {
   *aResult = Kind() == eSystemPrincipal;
   return NS_OK;
 }
 
 NS_IMETHODIMP
 BasePrincipal::GetJarPrefix(nsACString& aJarPrefix)
 {
-  mozilla::GetJarPrefix(mOriginAttributes.mAppId, mOriginAttributes.mInBrowser, aJarPrefix);
+  mozilla::GetJarPrefix(mOriginAttributes.mAppId, mOriginAttributes.mInIsolatedMozBrowser, aJarPrefix);
   return NS_OK;
 }
 
 NS_IMETHODIMP
 BasePrincipal::GetOriginAttributes(JSContext* aCx, JS::MutableHandle<JS::Value> aVal)
 {
   if (NS_WARN_IF(!ToJSValue(aCx, mOriginAttributes, aVal))) {
     return NS_ERROR_FAILURE;
@@ -518,19 +518,19 @@ BasePrincipal::GetAppId(uint32_t* aAppId
 NS_IMETHODIMP
 BasePrincipal::GetUserContextId(uint32_t* aUserContextId)
 {
   *aUserContextId = UserContextId();
   return NS_OK;
 }
 
 NS_IMETHODIMP
-BasePrincipal::GetIsInBrowserElement(bool* aIsInBrowserElement)
+BasePrincipal::GetIsInIsolatedMozBrowserElement(bool* aIsInIsolatedMozBrowserElement)
 {
-  *aIsInBrowserElement = IsInBrowserElement();
+  *aIsInIsolatedMozBrowserElement = IsInIsolatedMozBrowserElement();
   return NS_OK;
 }
 
 NS_IMETHODIMP
 BasePrincipal::GetUnknownAppId(bool* aUnknownAppId)
 {
   *aUnknownAppId = AppId() == nsIScriptSecurityManager::UNKNOWN_APP_ID;
   return NS_OK;

--- a/caps/BasePrincipal.h
+++ b/caps/BasePrincipal.h
@@ -25,17 +25,17 @@ namespace mozilla {
 // Base OriginAttributes class. This has several subclass flavors, and is not
 // directly constructable itself.
 class OriginAttributes : public dom::OriginAttributesDictionary
 {
 public:
   bool operator==(const OriginAttributes& aOther) const
   {
     return mAppId == aOther.mAppId &&
-           mInBrowser == aOther.mInBrowser &&
+           mInIsolatedMozBrowser == aOther.mInIsolatedMozBrowser &&
            mAddonId == aOther.mAddonId &&
            mUserContextId == aOther.mUserContextId &&
            mSignedPkg == aOther.mSignedPkg;
   }
   bool operator!=(const OriginAttributes& aOther) const
   {
     return !(*this == aOther);
   }
@@ -70,20 +70,20 @@ class NeckoOriginAttributes;
 // flavors, and a variety of InheritFrom* methods to implement the transfer
 // behavior.
 
 // For OriginAttributes stored on principals.
 class PrincipalOriginAttributes : public OriginAttributes
 {
 public:
   PrincipalOriginAttributes() {}
-  PrincipalOriginAttributes(uint32_t aAppId, bool aInBrowser)
+  PrincipalOriginAttributes(uint32_t aAppId, bool aInIsolatedMozBrowser)
   {
     mAppId = aAppId;
-    mInBrowser = aInBrowser;
+    mInIsolatedMozBrowser = aInIsolatedMozBrowser;
   }
 
   // Inheriting OriginAttributes from docshell to document when user navigates.
   //
   // @param aAttrs  Origin Attributes of the docshell.
   // @param aURI    The URI of the document.
   void InheritFromDocShellToDoc(const DocShellOriginAttributes& aAttrs,
                                 const nsIURI* aURI);
@@ -92,39 +92,39 @@ public:
   void InheritFromNecko(const NeckoOriginAttributes& aAttrs);
 };
 
 // For OriginAttributes stored on docshells / loadcontexts / browsing contexts.
 class DocShellOriginAttributes : public OriginAttributes
 {
 public:
   DocShellOriginAttributes() {}
-  DocShellOriginAttributes(uint32_t aAppId, bool aInBrowser)
+  DocShellOriginAttributes(uint32_t aAppId, bool aInIsolatedMozBrowser)
   {
     mAppId = aAppId;
-    mInBrowser = aInBrowser;
+    mInIsolatedMozBrowser = aInIsolatedMozBrowser;
   }
 
   // Inheriting OriginAttributes from document to child docshell when an
   // <iframe> is created.
   //
   // @param aAttrs  Origin Attributes of the document.
   void
   InheritFromDocToChildDocShell(const PrincipalOriginAttributes& aAttrs);
 };
 
 // For OriginAttributes stored on Necko.
 class NeckoOriginAttributes : public OriginAttributes
 {
 public:
   NeckoOriginAttributes() {}
-  NeckoOriginAttributes(uint32_t aAppId, bool aInBrowser)
+  NeckoOriginAttributes(uint32_t aAppId, bool aInIsolatedMozBrowser)
   {
     mAppId = aAppId;
-    mInBrowser = aInBrowser;
+    mInIsolatedMozBrowser = aInIsolatedMozBrowser;
   }
 
   // Inheriting OriginAttributes from document to necko when a network request
   // is made.
   void InheritFromDocToNecko(const PrincipalOriginAttributes& aAttrs);
 
   void InheritFromDocShellToNecko(const DocShellOriginAttributes& aAttrs);
 };
@@ -154,17 +154,17 @@ public:
 
   // Performs a match of |aAttrs| against this pattern.
   bool Matches(const OriginAttributes& aAttrs) const
   {
     if (mAppId.WasPassed() && mAppId.Value() != aAttrs.mAppId) {
       return false;
     }
 
-    if (mInBrowser.WasPassed() && mInBrowser.Value() != aAttrs.mInBrowser) {
+    if (mInIsolatedMozBrowser.WasPassed() && mInIsolatedMozBrowser.Value() != aAttrs.mInIsolatedMozBrowser) {
       return false;
     }
 
     if (mAddonId.WasPassed() && mAddonId.Value() != aAttrs.mAddonId) {
       return false;
     }
 
     if (mUserContextId.WasPassed() && mUserContextId.Value() != aAttrs.mUserContextId) {
@@ -210,33 +210,33 @@ public:
   NS_IMETHOD GetIsCodebasePrincipal(bool* aResult) override;
   NS_IMETHOD GetIsExpandedPrincipal(bool* aResult) override;
   NS_IMETHOD GetIsSystemPrincipal(bool* aResult) override;
   NS_IMETHOD GetJarPrefix(nsACString& aJarPrefix) final;
   NS_IMETHOD GetOriginAttributes(JSContext* aCx, JS::MutableHandle<JS::Value> aVal) final;
   NS_IMETHOD GetOriginSuffix(nsACString& aOriginSuffix) final;
   NS_IMETHOD GetAppStatus(uint16_t* aAppStatus) final;
   NS_IMETHOD GetAppId(uint32_t* aAppStatus) final;
-  NS_IMETHOD GetIsInBrowserElement(bool* aIsInBrowserElement) final;
+  NS_IMETHOD GetIsInIsolatedMozBrowserElement(bool* aIsInIsolatedMozBrowserElement) final;
   NS_IMETHOD GetUnknownAppId(bool* aUnknownAppId) final;
   NS_IMETHOD GetUserContextId(uint32_t* aUserContextId) final;
 
   virtual bool IsOnCSSUnprefixingWhitelist() override { return false; }
 
   virtual bool IsCodebasePrincipal() const { return false; };
 
   static BasePrincipal* Cast(nsIPrincipal* aPrin) { return static_cast<BasePrincipal*>(aPrin); }
   static already_AddRefed<BasePrincipal>
   CreateCodebasePrincipal(nsIURI* aURI, const PrincipalOriginAttributes& aAttrs);
   static already_AddRefed<BasePrincipal> CreateCodebasePrincipal(const nsACString& aOrigin);
 
   const PrincipalOriginAttributes& OriginAttributesRef() { return mOriginAttributes; }
   uint32_t AppId() const { return mOriginAttributes.mAppId; }
   uint32_t UserContextId() const { return mOriginAttributes.mUserContextId; }
-  bool IsInBrowserElement() const { return mOriginAttributes.mInBrowser; }
+  bool IsInIsolatedMozBrowserElement() const { return mOriginAttributes.mInIsolatedMozBrowser; }
 
   enum PrincipalKind {
     eNullPrincipal,
     eCodebasePrincipal,
     eExpandedPrincipal,
     eSystemPrincipal
   };
 

--- a/caps/nsIPrincipal.idl
+++ b/caps/nsIPrincipal.idl
@@ -298,20 +298,23 @@ interface nsIPrincipal : nsISerializable
     /**
      * Gets the id of the user context this principal is inside.  If this
      * principal is inside the default userContext, this returns
      * nsIScriptSecurityManager::DEFAULT_USER_CONTEXT_ID.
      */
     [infallible] readonly attribute unsigned long userContextId;
 
     /**
-     * Returns true iff the principal is inside a browser element.  (<iframe
-     * mozbrowser mozapp> does not count as a browser element.)
+     * Returns true iff the principal is inside an isolated mozbrowser element.
+     * <iframe mozbrowser mozapp> and <xul:browser> are not considered to be
+     * mozbrowser elements.  <iframe mozbrowser noisolation> does not count as
+     * isolated since isolation is disabled.  Isolation can only be disabled if
+     * the containing document is chrome.
      */
-    [infallible] readonly attribute boolean isInBrowserElement;
+    [infallible] readonly attribute boolean isInIsolatedMozBrowserElement;
 
     /**
      * Returns true if this principal has an unknown appId. This shouldn't
      * generally be used. We only expose it due to not providing the correct
      * appId everywhere where we construct principals.
      */
     [infallible] readonly attribute boolean unknownAppId;
 

--- a/caps/nsScriptSecurityManager.cpp
+++ b/caps/nsScriptSecurityManager.cpp
@@ -255,23 +255,35 @@ nsScriptSecurityManager::SecurityHashURI
 {
     return NS_SecurityHashURI(aURI);
 }
 
 uint16_t
 nsScriptSecurityManager::AppStatusForPrincipal(nsIPrincipal *aPrin)
 {
     uint32_t appId = aPrin->GetAppId();
-    bool inMozBrowser = aPrin->GetIsInBrowserElement();
+
+    // After bug 1238160, the principal no longer knows how to answer "is this a
+    // browser element", which is really what this code path wants. Currently,
+    // desktop is the only platform where we intend to disable isolation on a
+    // browser frame, so non-desktop should be able to assume that
+    // inIsolatedMozBrowser is true for all mozbrowser frames.  Additionally,
+    // apps are no longer used on desktop, so appId is always NO_APP_ID.  We use
+    // a release assertion in nsFrameLoader::OwnerIsIsolatedMozBrowserFrame so
+    // that platforms with apps can assume inIsolatedMozBrowser is true for all
+    // mozbrowser frames.
+    bool inIsolatedMozBrowser = aPrin->GetIsInIsolatedMozBrowserElement();
+
     NS_WARN_IF_FALSE(appId != nsIScriptSecurityManager::UNKNOWN_APP_ID,
                      "Asking for app status on a principal with an unknown app id");
     // Installed apps have a valid app id (not NO_APP_ID or UNKNOWN_APP_ID)
     // and they are not inside a mozbrowser.
     if (appId == nsIScriptSecurityManager::NO_APP_ID ||
-        appId == nsIScriptSecurityManager::UNKNOWN_APP_ID || inMozBrowser)
+        appId == nsIScriptSecurityManager::UNKNOWN_APP_ID ||
+        inIsolatedMozBrowser)
     {
         return nsIPrincipal::APP_STATUS_NOT_INSTALLED;
     }
 
     nsCOMPtr<nsIAppsService> appsService = do_GetService(APPS_SERVICE_CONTRACTID);
     NS_ENSURE_TRUE(appsService, nsIPrincipal::APP_STATUS_NOT_INSTALLED);
 
     nsCOMPtr<mozIApplication> app;
@@ -286,17 +298,17 @@ nsScriptSecurityManager::AppStatusForPri
     NS_ENSURE_SUCCESS(app->GetOrigin(appOrigin),
                       nsIPrincipal::APP_STATUS_NOT_INSTALLED);
     nsCOMPtr<nsIURI> appURI;
     NS_ENSURE_SUCCESS(NS_NewURI(getter_AddRefs(appURI), appOrigin),
                       nsIPrincipal::APP_STATUS_NOT_INSTALLED);
 
     // The app could contain a cross-origin iframe - make sure that the content
     // is actually same-origin with the app.
-    MOZ_ASSERT(inMozBrowser == false, "Checked this above");
+    MOZ_ASSERT(inIsolatedMozBrowser == false, "Checked this above");
     PrincipalOriginAttributes attrs(appId, false);
     nsCOMPtr<nsIPrincipal> appPrin = BasePrincipal::CreateCodebasePrincipal(appURI, attrs);
     NS_ENSURE_TRUE(appPrin, nsIPrincipal::APP_STATUS_NOT_INSTALLED);
     return aPrin->Equals(appPrin) ? status
                                   : nsIPrincipal::APP_STATUS_NOT_INSTALLED;
 }
 
 /*
@@ -585,17 +597,17 @@ nsScriptSecurityManager::CheckLoadURIFro
  * CheckLoadURIWithPrincipal means denying loading if the given URI has certain
  * nsIProtocolHandler flags set.
  * @return if success, access is allowed. Otherwise, deny access
  */
 static nsresult
 DenyAccessIfURIHasFlags(nsIURI* aURI, uint32_t aURIFlags)
 {
     NS_PRECONDITION(aURI, "Must have URI!");
-    
+
     bool uriHasFlags;
     nsresult rv =
         NS_URIChainHasFlags(aURI, aURIFlags, &uriHasFlags);
     NS_ENSURE_SUCCESS(rv, rv);
 
     if (uriHasFlags) {
         return NS_ERROR_DOM_BAD_URI;
     }
@@ -719,17 +731,17 @@ nsScriptSecurityManager::CheckLoadURIWit
             }
             // None of our whitelisted principals worked.
             return NS_ERROR_DOM_BAD_URI;
         }
         NS_ERROR("Non-system principals or expanded principal passed to CheckLoadURIWithPrincipal "
                  "must have a URI!");
         return NS_ERROR_UNEXPECTED;
     }
-    
+
     // Automatic loads are not allowed from certain protocols.
     if (aFlags & nsIScriptSecurityManager::LOAD_IS_AUTOMATIC_DOCUMENT_REPLACEMENT) {
         nsresult rv =
             DenyAccessIfURIHasFlags(sourceURI,
                                     nsIProtocolHandler::URI_FORBIDS_AUTOMATIC_DOCUMENT_REPLACEMENT);
         NS_ENSURE_SUCCESS(rv, rv);
     }
 
@@ -953,17 +965,17 @@ nsScriptSecurityManager::CheckLoadURIWit
         if (NS_SUCCEEDED(rv)) {
             nsCOMPtr<nsIConsoleService> console(
               do_GetService("@mozilla.org/consoleservice;1"));
             NS_ENSURE_TRUE(console, NS_ERROR_FAILURE);
 
             console->LogStringMessage(message.get());
         }
     }
-    
+
     return NS_OK;
 }
 
 nsresult
 nsScriptSecurityManager::ReportError(JSContext* cx, const nsAString& messageTag,
                                      nsIURI* aSource, nsIURI* aTarget)
 {
     nsresult rv;
@@ -1165,23 +1177,23 @@ nsScriptSecurityManager::CreateExpandedP
   nsCOMPtr<nsIPrincipal> p = new nsExpandedPrincipal(principals);
   p.forget(aResult);
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsScriptSecurityManager::GetAppCodebasePrincipal(nsIURI* aURI,
                                                  uint32_t aAppId,
-                                                 bool aInMozBrowser,
+                                                 bool aInIsolatedMozBrowser,
                                                  nsIPrincipal** aPrincipal)
 {
   NS_ENSURE_TRUE(aAppId != nsIScriptSecurityManager::UNKNOWN_APP_ID,
                  NS_ERROR_INVALID_ARG);
 
-  PrincipalOriginAttributes attrs(aAppId, aInMozBrowser);
+  PrincipalOriginAttributes attrs(aAppId, aInIsolatedMozBrowser);
   nsCOMPtr<nsIPrincipal> prin = BasePrincipal::CreateCodebasePrincipal(aURI, attrs);
   prin.forget(aPrincipal);
   return *aPrincipal ? NS_OK : NS_ERROR_FAILURE;
 }
 
 NS_IMETHODIMP
 nsScriptSecurityManager::
   GetLoadContextCodebasePrincipal(nsIURI* aURI,
@@ -1561,50 +1573,50 @@ nsScriptSecurityManager::InitPrefs()
     Preferences::AddStrongObservers(this, kObservedPrefs);
 
     return NS_OK;
 }
 
 namespace mozilla {
 
 void
-GetJarPrefix(uint32_t aAppId, bool aInMozBrowser, nsACString& aJarPrefix)
+GetJarPrefix(uint32_t aAppId, bool aInIsolatedMozBrowser, nsACString& aJarPrefix)
 {
   MOZ_ASSERT(aAppId != nsIScriptSecurityManager::UNKNOWN_APP_ID);
 
   if (aAppId == nsIScriptSecurityManager::UNKNOWN_APP_ID) {
     aAppId = nsIScriptSecurityManager::NO_APP_ID;
   }
 
   aJarPrefix.Truncate();
 
   // Fallback.
-  if (aAppId == nsIScriptSecurityManager::NO_APP_ID && !aInMozBrowser) {
+  if (aAppId == nsIScriptSecurityManager::NO_APP_ID && !aInIsolatedMozBrowser) {
     return;
   }
 
   // aJarPrefix = appId + "+" + { 't', 'f' } + "+";
   aJarPrefix.AppendInt(aAppId);
   aJarPrefix.Append('+');
-  aJarPrefix.Append(aInMozBrowser ? 't' : 'f');
+  aJarPrefix.Append(aInIsolatedMozBrowser ? 't' : 'f');
   aJarPrefix.Append('+');
 
   return;
 }
 
 } // namespace mozilla
 
 NS_IMETHODIMP
 nsScriptSecurityManager::GetJarPrefix(uint32_t aAppId,
-                                      bool aInMozBrowser,
+                                      bool aInIsolatedMozBrowser,
                                       nsACString& aJarPrefix)
 {
   MOZ_ASSERT(aAppId != nsIScriptSecurityManager::UNKNOWN_APP_ID);
 
-  mozilla::GetJarPrefix(aAppId, aInMozBrowser, aJarPrefix);
+  mozilla::GetJarPrefix(aAppId, aInIsolatedMozBrowser, aJarPrefix);
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsScriptSecurityManager::GetDomainPolicyActive(bool *aRv)
 {
     *aRv = !!mDomainPolicy;
     return NS_OK;
@@ -1689,9 +1701,8 @@ nsScriptSecurityManager::PolicyAllowsScr
     rv = superExceptions->ContainsSuperDomain(aURI, &contains);
     NS_ENSURE_SUCCESS(rv, rv);
     if (contains) {
         *aRv = !*aRv;
     }
 
     return NS_OK;
 }
-

--- a/caps/nsScriptSecurityManager.h
+++ b/caps/nsScriptSecurityManager.h
@@ -146,14 +146,14 @@ private:
     static nsIStringBundle *sStrBundle;
     static JSRuntime       *sRuntime;
 };
 
 namespace mozilla {
 
 void
 GetJarPrefix(uint32_t aAppid,
-             bool aInMozBrowser,
+             bool aInIsolatedMozBrowser,
              nsACString& aJarPrefix);
 
 } // namespace mozilla
 
 #endif // nsScriptSecurityManager_h__

--- a/caps/tests/gtest/TestOriginAttributes.cpp
+++ b/caps/tests/gtest/TestOriginAttributes.cpp
@@ -19,19 +19,19 @@ TestSuffix(const PrincipalOriginAttribut
 }
 
 TEST(PrincipalOriginAttributes, Suffix_default)
 {
   PrincipalOriginAttributes attrs;
   TestSuffix(attrs);
 }
 
-TEST(PrincipalOriginAttributes, Suffix_appId_inBrowser)
+TEST(PrincipalOriginAttributes, Suffix_appId_inIsolatedMozBrowser)
 {
   PrincipalOriginAttributes attrs(1, true);
   TestSuffix(attrs);
 }
 
-TEST(PrincipalOriginAttributes, Suffix_maxAppId_inBrowser)
+TEST(PrincipalOriginAttributes, Suffix_maxAppId_inIsolatedMozBrowser)
 {
   PrincipalOriginAttributes attrs(4294967295, true);
   TestSuffix(attrs);
 }

--- a/caps/tests/mochitest/test_principal_jarprefix_origin_appid_appstatus.html
+++ b/caps/tests/mochitest/test_principal_jarprefix_origin_appid_appstatus.html
@@ -28,16 +28,18 @@ SimpleTest.waitForExplicitFinish();
  * - app: gives the app manifest URL, will set mozapp to it on the iframe;
  * - origin: gives the origin of the iframe. This is the URL thas is going to
  *           to be passed as iframe.src but also the expected principal's
  *           origin.
  * - isapp: tells if the iframe is really a mozapp. If the manifest url isn't
  *          valid, the iframe will not be considered as a mozapp.
  * - browser: say if the iframe should be a mozbrowser. This is implicit when
  *            app is set.
+ * - isolated: if origin isolation is enabled with browser frames.  Defaults to
+ *             true if unset.
  * - test: an array of tests to run for this test case:
  *   - eo-unique: the extendedOrigin of the prinicpal must be unique in the
  *                current list.
  *   - eo-as-last: the extendedOrigin of the principal must be the same as the
  *                 last added to the list.
  */
 var gData = [
   {
@@ -225,25 +227,68 @@ var gData = [
     browser: false,
     child: {
       src: "http://example.org/chrome/",
       isapp: false,
       browser: true,
     },
     test: [ "child-has-different-eo", "child-has-same-appstatus", "child-has-same-appid" ],
   },
-  // browser containing an iframe is part of the browser
+  // browser containing an iframe that is part of the browser
   {
     src: "http://example.org/",
     isapp: false,
     browser: true,
     child: {
       src: "http://example.org/chrome/",
       isapp: false,
-      inBrowser: true,
+      inIsolatedMozBrowser: true,
+    },
+    test: [ "child-has-same-eo" ],
+  },
+  // iframe containing a browser with isolation disabled
+  // (only chrome documents can disable isolation)
+  {
+    src: "http://example.org/",
+    isapp: false,
+    browser: false,
+    child: {
+      src: "http://example.org/chrome/",
+      isapp: false,
+      browser: true,
+      isolated: false,
+      inIsolatedMozBrowser: true,
+    },
+    test: [ "child-has-different-eo" ],
+  },
+  // browser with isolation disabled containing an iframe that is part of the browser
+  {
+    src: "http://example.org/",
+    isapp: false,
+    browser: true,
+    isolated: false,
+    child: {
+      src: "http://example.org/chrome/",
+      isapp: false,
+      inIsolatedMozBrowser: false,
+    },
+    test: [ "child-has-same-eo" ],
+  },
+  // iframe with isolation enabled containing an iframe with isolation disabled
+  // (isolated only has an effect on browsers)
+  {
+    src: "http://example.org/",
+    isapp: false,
+    browser: false,
+    isolated: true,
+    child: {
+      src: "http://example.org/chrome/",
+      isapp: false,
+      browser: false,
+      isolated: false,
     },
     test: [ "child-has-same-eo" ],
   },
 ];
 
 // The list of all data ids generated by this test.
 var eoList = [];
 
@@ -275,46 +320,60 @@ function checkIFrame(aFrame, data) {
     }
   } else {
     is(principal.appStatus, Ci.nsIPrincipal.APP_STATUS_NOT_INSTALLED,
        'this should not be an installed app');
     is(principal.appId, Ci.nsIScriptSecurityManager.NO_APP_ID,
        "principals from non-installed app should have NO_APP_ID");
   }
 
-  if (!data.isapp && !data.browser) {
+  if (!data.isapp && !data.browser ||
+      (data.browser && data.isolated === false)) {
     is(principal.jarPrefix, "",
-       'jarPrefix should return an empty string for non-app and non-browsers principals');
+       "jarPrefix should return an empty string for non-app, non-browsers, " +
+       "and browsers with isolation disabled");
   } else {
     isnot(principal.jarPrefix, "",
-          'jarPrefix should not return an empty string for apps or mozbrowsers');
+          "jarPrefix should not return an empty string for apps or browsers " +
+          "with isolation enabled");
   }
 
   if (data.test.indexOf("eo-unique") != -1) {
     is(eoList.indexOf(principal.jarPrefix + principal.origin), -1,
        "extended origin should be unique");
   }
   if (data.test.indexOf("eo-as-last") != -1) {
     is(principal.jarPrefix + principal.origin, eoList[eoList.length-1],
        "extended origin should be the same as the last inserted one");
   }
 
-  is(principal.isInBrowserElement, !!data.browser,
-     "check principal.isInBrowserElement");
+  let isolationExpected = false;
+  if (data.isolated !== false) {
+    isolationExpected = !!data.browser;
+  }
+  is(principal.isInIsolatedMozBrowserElement, isolationExpected,
+     "check principal.isInIsolatedMozBrowserElement");
 
   if (data.child) {
     let childPrincipal = aFrame.contentWindow.frames[0].document.nodePrincipal;
 
     if (data.child.isapp) {
       is(childPrincipal.appStatus, Ci.nsIPrincipal.APP_STATUS_INSTALLED,
          "child should be an installed app");
     }
 
-    is(childPrincipal.isInBrowserElement, !!data.child.browser || !!data.child.inBrowser,
-       "check childPrincipal.isInBrowserElement");
+    let childIsolationExpected = false;
+    if (data.child.isolated !== false) {
+      childIsolationExpected = !!data.child.browser;
+    }
+    if (data.child.inIsolatedMozBrowser !== undefined) {
+      childIsolationExpected = data.child.inIsolatedMozBrowser;
+    }
+    is(childPrincipal.isInIsolatedMozBrowserElement, childIsolationExpected,
+       "check childPrincipal.isInIsolatedMozBrowserElement");
 
     if (data.test.indexOf("child-has-same-eo") != -1) {
       is(childPrincipal.jarPrefix + childPrincipal.origin,
          principal.jarPrefix + principal.origin,
          "child should have the same extended origin as parent");
       is(childPrincipal.appStatus, principal.appStatus,
          "child should have the same appStatus if it has the same extended origin");
       is(childPrincipal.appId, principal.appId,
@@ -387,46 +446,55 @@ function runTest() {
 
       if (data.child.app) {
         childFrame.setAttribute('mozapp', data.child.app)
         childFrame.setAttribute('mozbrowser', '');
       } else if (data.child.browser) {
         childFrame.setAttribute('mozbrowser', '');
       }
 
+      if (data.child.isolated === false) {
+        childFrame.setAttribute("noisolation", "");
+      }
+
       childFrame.src = data.child.src;
 
       this.removeEventListener('load', this.addChild.bind(this));
       childFrame.addEventListener('load', this.check.bind(this));
 
       this.contentDocument.body.appendChild(childFrame);
     };
 
     if (data.app) {
       iframe.setAttribute('mozapp', data.app);
       iframe.setAttribute('mozbrowser', '');
     } else if (data.browser) {
       iframe.setAttribute('mozbrowser', '');
     }
 
+    if (data.isolated === false) {
+      iframe.setAttribute("noisolation", "");
+    }
+
     iframe.src = data.src;
 
     if (data.child) {
       iframe.addEventListener('load', iframe.addChild.bind(iframe));
     } else {
       iframe.addEventListener('load', iframe.check.bind(iframe));
     }
 
     content.appendChild(iframe);
 
     yield;
   }
 }
 
 var gTestRunner = runTest();
 
-SpecialPowers.pushPrefEnv({'set':[["dom.mozBrowserFramesEnabled", true]]},
-                           function() { gTestRunner.next(); });
+SpecialPowers.pushPrefEnv({"set": [
+  ["dom.mozBrowserFramesEnabled", true],
+]}, function() { gTestRunner.next(); });
 
 </script>
 </pre>
 </body>
 </html>

--- a/caps/tests/unit/test_origin.js
+++ b/caps/tests/unit/test_origin.js
@@ -19,45 +19,45 @@ function checkCrossOrigin(a, b) {
   do_check_false(a.subsumesConsideringDomain(b));
   do_check_false(b.subsumes(a));
   do_check_false(b.subsumesConsideringDomain(a));
 }
 
 function checkOriginAttributes(prin, attrs, suffix) {
   attrs = attrs || {};
   do_check_eq(prin.originAttributes.appId, attrs.appId || 0);
-  do_check_eq(prin.originAttributes.inBrowser, attrs.inBrowser || false);
+  do_check_eq(prin.originAttributes.inIsolatedMozBrowser, attrs.inIsolatedMozBrowser || false);
   do_check_eq(prin.originSuffix, suffix || '');
   do_check_eq(ChromeUtils.originAttributesToSuffix(attrs), suffix || '');
   do_check_true(ChromeUtils.originAttributesMatchPattern(prin.originAttributes, attrs));
   if (!prin.isNullPrincipal && !prin.origin.startsWith('[')) {
     do_check_true(ssm.createCodebasePrincipalFromOrigin(prin.origin).equals(prin));
   } else {
     checkThrows(() => ssm.createCodebasePrincipalFromOrigin(prin.origin));
   }
 }
 
 // utility function useful for debugging
 function printAttrs(name, attrs) {
   do_print(name + " {\n" +
            "\tappId: " + attrs.appId + ",\n" +
            "\tuserContextId: " + attrs.userContextId + ",\n" +
-           "\tinBrowser: " + attrs.inBrowser + ",\n" +
+           "\tinIsolatedMozBrowser: " + attrs.inIsolatedMozBrowser + ",\n" +
            "\taddonId: '" + attrs.addonId + "',\n" +
            "\tsignedPkg: '" + attrs.signedPkg + "'\n}");
 }
 
 
 function checkValues(attrs, values) {
   values = values || {};
   //printAttrs("attrs", attrs);
   //printAttrs("values", values);
   do_check_eq(attrs.appId, values.appId || 0);
   do_check_eq(attrs.userContextId, values.userContextId || 0);
-  do_check_eq(attrs.inBrowser, values.inBrowser || false);
+  do_check_eq(attrs.inIsolatedMozBrowser, values.inIsolatedMozBrowser || false);
   do_check_eq(attrs.addonId, values.addonId || '');
   do_check_eq(attrs.signedPkg, values.signedPkg || '');
 }
 
 function run_test() {
   // Attributeless origins.
   do_check_eq(ssm.getSystemPrincipal().origin, '[System Principal]');
   checkOriginAttributes(ssm.getSystemPrincipal());
@@ -94,32 +94,32 @@ function run_test() {
   // Just app.
   var exampleOrg_app = ssm.createCodebasePrincipal(makeURI('http://example.org'), {appId: 42});
   var nullPrin_app = ssm.createNullPrincipal({appId: 42});
   checkOriginAttributes(exampleOrg_app, {appId: 42}, '^appId=42');
   checkOriginAttributes(nullPrin_app, {appId: 42}, '^appId=42');
   do_check_eq(exampleOrg_app.origin, 'http://example.org^appId=42');
 
   // Just browser.
-  var exampleOrg_browser = ssm.createCodebasePrincipal(makeURI('http://example.org'), {inBrowser: true});
-  var nullPrin_browser = ssm.createNullPrincipal({inBrowser: true});
-  checkOriginAttributes(exampleOrg_browser, {inBrowser: true}, '^inBrowser=1');
-  checkOriginAttributes(nullPrin_browser, {inBrowser: true}, '^inBrowser=1');
+  var exampleOrg_browser = ssm.createCodebasePrincipal(makeURI('http://example.org'), {inIsolatedMozBrowser: true});
+  var nullPrin_browser = ssm.createNullPrincipal({inIsolatedMozBrowser: true});
+  checkOriginAttributes(exampleOrg_browser, {inIsolatedMozBrowser: true}, '^inBrowser=1');
+  checkOriginAttributes(nullPrin_browser, {inIsolatedMozBrowser: true}, '^inBrowser=1');
   do_check_eq(exampleOrg_browser.origin, 'http://example.org^inBrowser=1');
 
   // App and browser.
-  var exampleOrg_appBrowser = ssm.createCodebasePrincipal(makeURI('http://example.org'), {inBrowser: true, appId: 42});
-  var nullPrin_appBrowser = ssm.createNullPrincipal({inBrowser: true, appId: 42});
-  checkOriginAttributes(exampleOrg_appBrowser, {appId: 42, inBrowser: true}, '^appId=42&inBrowser=1');
-  checkOriginAttributes(nullPrin_appBrowser, {appId: 42, inBrowser: true}, '^appId=42&inBrowser=1');
+  var exampleOrg_appBrowser = ssm.createCodebasePrincipal(makeURI('http://example.org'), {inIsolatedMozBrowser: true, appId: 42});
+  var nullPrin_appBrowser = ssm.createNullPrincipal({inIsolatedMozBrowser: true, appId: 42});
+  checkOriginAttributes(exampleOrg_appBrowser, {appId: 42, inIsolatedMozBrowser: true}, '^appId=42&inBrowser=1');
+  checkOriginAttributes(nullPrin_appBrowser, {appId: 42, inIsolatedMozBrowser: true}, '^appId=42&inBrowser=1');
   do_check_eq(exampleOrg_appBrowser.origin, 'http://example.org^appId=42&inBrowser=1');
 
   // App and browser, different domain.
-  var exampleCom_appBrowser = ssm.createCodebasePrincipal(makeURI('https://www.example.com:123'), {appId: 42, inBrowser: true});
-  checkOriginAttributes(exampleCom_appBrowser, {appId: 42, inBrowser: true}, '^appId=42&inBrowser=1');
+  var exampleCom_appBrowser = ssm.createCodebasePrincipal(makeURI('https://www.example.com:123'), {appId: 42, inIsolatedMozBrowser: true});
+  checkOriginAttributes(exampleCom_appBrowser, {appId: 42, inIsolatedMozBrowser: true}, '^appId=42&inBrowser=1');
   do_check_eq(exampleCom_appBrowser.origin, 'https://www.example.com:123^appId=42&inBrowser=1');
 
   // Addon.
   var exampleOrg_addon = ssm.createCodebasePrincipal(makeURI('http://example.org'), {addonId: 'dummy'});
   checkOriginAttributes(exampleOrg_addon, { addonId: "dummy" }, '^addonId=dummy');
   do_check_eq(exampleOrg_addon.origin, 'http://example.org^addonId=dummy');
 
   // Make sure we don't crash when serializing principals with UNKNOWN_APP_ID.
@@ -156,18 +156,18 @@ function run_test() {
   do_check_eq(exampleOrg_userContextApp.origin, 'http://example.org^appId=24&userContextId=42');
 
   // Just signedPkg
   var exampleOrg_signedPkg = ssm.createCodebasePrincipal(makeURI('http://example.org'), {signedPkg: 'whatever'});
   checkOriginAttributes(exampleOrg_signedPkg, { signedPkg: 'whatever' }, '^signedPkg=whatever');
   do_check_eq(exampleOrg_signedPkg.origin, 'http://example.org^signedPkg=whatever');
 
   // signedPkg and browser
-  var exampleOrg_signedPkg_browser = ssm.createCodebasePrincipal(makeURI('http://example.org'), {signedPkg: 'whatever', inBrowser: true});
-  checkOriginAttributes(exampleOrg_signedPkg_browser, { signedPkg: 'whatever', inBrowser: true }, '^inBrowser=1&signedPkg=whatever');
+  var exampleOrg_signedPkg_browser = ssm.createCodebasePrincipal(makeURI('http://example.org'), {signedPkg: 'whatever', inIsolatedMozBrowser: true});
+  checkOriginAttributes(exampleOrg_signedPkg_browser, { signedPkg: 'whatever', inIsolatedMozBrowser: true }, '^inBrowser=1&signedPkg=whatever');
   do_check_eq(exampleOrg_signedPkg_browser.origin, 'http://example.org^inBrowser=1&signedPkg=whatever');
 
   // Just signedPkg (but different value from 'exampleOrg_signedPkg_app')
   var exampleOrg_signedPkg_another = ssm.createCodebasePrincipal(makeURI('http://example.org'), {signedPkg: 'whatup'});
 
   // Check that all of the above are cross-origin.
   checkCrossOrigin(exampleOrg_app, exampleOrg);
   checkCrossOrigin(exampleOrg_app, nullPrin_app);
@@ -207,20 +207,20 @@ function run_test() {
   checkValues(emptyAttrs);
 
   var uri = "http://example.org";
   var tests = [
     [ "", {} ],
     [ "^appId=5", {appId: 5} ],
     [ "^userContextId=3", {userContextId: 3} ],
     [ "^addonId=fooBar", {addonId: "fooBar"} ],
-    [ "^inBrowser=1", {inBrowser: true} ],
+    [ "^inBrowser=1", {inIsolatedMozBrowser: true} ],
     [ "^signedPkg=bazQux", {signedPkg: "bazQux"} ],
     [ "^appId=3&inBrowser=1&userContextId=6",
-      {appId: 3, userContextId: 6, inBrowser: true} ] ];
+      {appId: 3, userContextId: 6, inIsolatedMozBrowser: true} ] ];
 
   // check that we can create an origin attributes from an origin properly
   tests.forEach(function(t) {
     let attrs = ChromeUtils.createOriginAttributesFromOrigin(uri + t[0]);
     checkValues(attrs, t[1]);
     do_check_eq(ChromeUtils.originAttributesToSuffix(attrs), t[0]);
   });
 

--- a/devtools/client/netmonitor/test/browser.ini
+++ b/devtools/client/netmonitor/test/browser.ini
@@ -109,16 +109,17 @@ skip-if = e10s # Bug 1091612
 [browser_net_security-warnings.js]
 [browser_net_send-beacon.js]
 [browser_net_send-beacon-other-tab.js]
 [browser_net_simple-init.js]
 [browser_net_simple-request-data.js]
 [browser_net_simple-request-details.js]
 [browser_net_simple-request.js]
 [browser_net_sort-01.js]
+skip-if = (e10s && debug && os == 'mac') # Bug 1253037
 [browser_net_sort-02.js]
 [browser_net_sort-03.js]
 [browser_net_statistics-01.js]
 [browser_net_statistics-02.js]
 [browser_net_statistics-03.js]
 [browser_net_status-codes.js]
 [browser_net_timeline_ticks.js]
 [browser_net_timing-division.js]

--- a/devtools/shared/layout/utils.js
+++ b/devtools/shared/layout/utils.js
@@ -29,17 +29,17 @@ const utilsFor = memoize(
  * @param {DOMWindow} win
  * @return {DOMWindow}
  */
 function getTopWindow(win) {
   let docShell = win.QueryInterface(Ci.nsIInterfaceRequestor)
                     .getInterface(Ci.nsIWebNavigation)
                     .QueryInterface(Ci.nsIDocShell);
 
-  if (!docShell.isBrowserOrApp) {
+  if (!docShell.isMozBrowserOrApp) {
     return win.top;
   }
 
   let topDocShell = docShell.getSameTypeRootTreeItemIgnoreBrowserAndAppBoundaries();
 
   return topDocShell
           ? topDocShell.contentViewer.DOMDocument.defaultView
           : null;
@@ -89,17 +89,17 @@ function getParentWindow(win) {
   if (isTopWindow(win)) {
     return null;
   }
 
   let docShell = win.QueryInterface(Ci.nsIInterfaceRequestor)
                  .getInterface(Ci.nsIWebNavigation)
                  .QueryInterface(Ci.nsIDocShell);
 
-  if (!docShell.isBrowserOrApp) {
+  if (!docShell.isMozBrowserOrApp) {
     return win.parent;
   }
 
   let parentDocShell = docShell.getSameTypeParentIgnoreBrowserAndAppBoundaries();
 
   return parentDocShell
           ? parentDocShell.contentViewer.DOMDocument.defaultView
           : null;

--- a/docshell/base/LoadContext.cpp
+++ b/docshell/base/LoadContext.cpp
@@ -29,17 +29,17 @@ nsILoadContext::GetOriginAttributes(mozi
   JSAutoCompartment ac(jsapi.cx(), obj);
 
   mozilla::DocShellOriginAttributes attrs;
   ok = attrs.Init(jsapi.cx(), v);
   NS_ENSURE_TRUE(ok, false);
   aAttrs = attrs;
   return true;
 }
-  
+
 namespace mozilla {
 
 NS_IMPL_ISUPPORTS(LoadContext, nsILoadContext, nsIInterfaceRequestor)
 
 LoadContext::LoadContext(nsIPrincipal* aPrincipal,
                          nsILoadContext* aOptionalBase)
   : mTopFrameElement(nullptr)
   , mNestedFrameId(0)
@@ -167,23 +167,23 @@ LoadContext::SetRemoteTabs(bool aUseRemo
 {
   MOZ_ASSERT(mIsNotNull);
 
   // We shouldn't need this on parent...
   return NS_ERROR_UNEXPECTED;
 }
 
 NS_IMETHODIMP
-LoadContext::GetIsInBrowserElement(bool* aIsInBrowserElement)
+LoadContext::GetIsInIsolatedMozBrowserElement(bool* aIsInIsolatedMozBrowserElement)
 {
   MOZ_ASSERT(mIsNotNull);
 
-  NS_ENSURE_ARG_POINTER(aIsInBrowserElement);
+  NS_ENSURE_ARG_POINTER(aIsInIsolatedMozBrowserElement);
 
-  *aIsInBrowserElement = mOriginAttributes.mInBrowser;
+  *aIsInIsolatedMozBrowserElement = mOriginAttributes.mInIsolatedMozBrowser;
   return NS_OK;
 }
 
 NS_IMETHODIMP
 LoadContext::GetAppId(uint32_t* aAppId)
 {
   MOZ_ASSERT(mIsNotNull);
 

--- a/docshell/base/LoadContext.h
+++ b/docshell/base/LoadContext.h
@@ -34,35 +34,35 @@ class LoadContext final
   : public nsILoadContext
   , public nsIInterfaceRequestor
 {
 public:
   NS_DECL_ISUPPORTS
   NS_DECL_NSILOADCONTEXT
   NS_DECL_NSIINTERFACEREQUESTOR
 
-  // AppId/inBrowser arguments override those in SerializedLoadContext provided
-  // by child process.
+  // appId/inIsolatedMozBrowser arguments override those in SerializedLoadContext
+  // provided by child process.
   LoadContext(const IPC::SerializedLoadContext& aToCopy,
               dom::Element* aTopFrameElement,
               DocShellOriginAttributes& aAttrs)
     : mTopFrameElement(do_GetWeakReference(aTopFrameElement))
     , mNestedFrameId(0)
     , mIsContent(aToCopy.mIsContent)
     , mUsePrivateBrowsing(aToCopy.mUsePrivateBrowsing)
     , mUseRemoteTabs(aToCopy.mUseRemoteTabs)
     , mOriginAttributes(aAttrs)
 #ifdef DEBUG
     , mIsNotNull(aToCopy.mIsNotNull)
 #endif
   {
   }
 
-  // AppId/inBrowser arguments override those in SerializedLoadContext provided
-  // by child process.
+  // appId/inIsolatedMozBrowser arguments override those in SerializedLoadContext
+  // provided by child process.
   LoadContext(const IPC::SerializedLoadContext& aToCopy,
               uint64_t aNestedFrameId,
               DocShellOriginAttributes& aAttrs)
     : mTopFrameElement(nullptr)
     , mNestedFrameId(aNestedFrameId)
     , mIsContent(aToCopy.mIsContent)
     , mUsePrivateBrowsing(aToCopy.mUsePrivateBrowsing)
     , mUseRemoteTabs(aToCopy.mUseRemoteTabs)

--- a/docshell/base/nsDSURIContentListener.cpp
+++ b/docshell/base/nsDSURIContentListener.cpp
@@ -327,17 +327,17 @@ nsDSURIContentListener::CheckOneFrameOpt
 
   // Traverse up the parent chain and stop when we see a docshell whose
   // parent has a system principal, or a docshell corresponding to
   // <iframe mozbrowser>.
   while (NS_SUCCEEDED(
            curDocShellItem->GetParent(getter_AddRefs(parentDocShellItem))) &&
          parentDocShellItem) {
     nsCOMPtr<nsIDocShell> curDocShell = do_QueryInterface(curDocShellItem);
-    if (curDocShell && curDocShell->GetIsBrowserOrApp()) {
+    if (curDocShell && curDocShell->GetIsMozBrowserOrApp()) {
       break;
     }
 
     bool system = false;
     topDoc = parentDocShellItem->GetDocument();
     if (topDoc) {
       if (NS_SUCCEEDED(
             ssm->IsSystemPrincipal(topDoc->NodePrincipal(), &system)) &&

--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -775,16 +775,17 @@ nsDocShell::nsDocShell()
   , mAllowContentRetargetingOnChildren(true)
   , mCreatingDocument(false)
   , mUseErrorPages(false)
   , mObserveErrorPages(true)
   , mAllowAuth(true)
   , mAllowKeywordFixup(false)
   , mIsOffScreenBrowser(false)
   , mIsActive(true)
+  , mDisableMetaRefreshWhenInactive(false)
   , mIsPrerendered(false)
   , mIsAppTab(false)
   , mUseGlobalHistory(false)
   , mInPrivateBrowsing(false)
   , mUseRemoteTabs(false)
   , mDeviceSizeIsPageSize(false)
   , mWindowDraggingAllowed(false)
   , mInFrameSwap(false)
@@ -800,16 +801,17 @@ nsDocShell::nsDocShell()
   , mInEnsureScriptEnv(false)
 #endif
   , mAffectPrivateSessionLifetime(true)
   , mInvisible(false)
   , mHasLoadedNonBlankURI(false)
   , mDefaultLoadFlags(nsIRequest::LOAD_NORMAL)
   , mBlankTiming(false)
   , mFrameType(eFrameTypeRegular)
+  , mIsInIsolatedMozBrowser(false)
   , mOwnOrContainingAppId(nsIScriptSecurityManager::UNKNOWN_APP_ID)
   , mUserContextId(nsIScriptSecurityManager::DEFAULT_USER_CONTEXT_ID)
   , mParentCharsetSource(0)
   , mJSRunToCompletionDepth(0)
 {
   mHistoryID = ++gDocshellIDCounter;
   if (gDocShellCount++ == 0) {
     NS_ASSERTION(sURIFixup == nullptr,
@@ -879,26 +881,23 @@ nsresult
 nsDocShell::Init()
 {
   nsresult rv = nsDocLoader::Init();
   NS_ENSURE_SUCCESS(rv, rv);
 
   NS_ASSERTION(mLoadGroup, "Something went wrong!");
 
   mContentListener = new nsDSURIContentListener(this);
-  NS_ENSURE_TRUE(mContentListener, NS_ERROR_OUT_OF_MEMORY);
-
   rv = mContentListener->Init();
   NS_ENSURE_SUCCESS(rv, rv);
 
   // We want to hold a strong ref to the loadgroup, so it better hold a weak
   // ref to us...  use an InterfaceRequestorProxy to do this.
   nsCOMPtr<nsIInterfaceRequestor> proxy =
     new InterfaceRequestorProxy(static_cast<nsIInterfaceRequestor*>(this));
-  NS_ENSURE_TRUE(proxy, NS_ERROR_OUT_OF_MEMORY);
   mLoadGroup->SetNotificationCallbacks(proxy);
 
   rv = nsDocLoader::AddDocLoaderAsChildOfRoot(this);
   NS_ENSURE_SUCCESS(rv, rv);
 
   // Add as |this| a progress listener to itself.  A little weird, but
   // simpler than reproducing all the listener-notification logic in
   // overrides of the various methods via which nsDocLoader can be
@@ -1645,17 +1644,16 @@ nsDocShell::LoadStream(nsIInputStream* a
                     NS_ERROR_FAILURE);
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsDocShell::CreateLoadInfo(nsIDocShellLoadInfo** aLoadInfo)
 {
   nsDocShellLoadInfo* loadInfo = new nsDocShellLoadInfo();
-  NS_ENSURE_TRUE(loadInfo, NS_ERROR_OUT_OF_MEMORY);
   nsCOMPtr<nsIDocShellLoadInfo> localRef(loadInfo);
 
   localRef.forget(aLoadInfo);
   return NS_OK;
 }
 
 /*
  * Reset state to a new content model within the current document and the
@@ -2551,17 +2549,17 @@ nsDocShell::GetFullscreenAllowed(bool* a
   // Otherwise, we have a parent, continue the checking for
   // mozFullscreenAllowed in the parent docshell's ancestors.
   return parent->GetFullscreenAllowed(aFullscreenAllowed);
 }
 
 NS_IMETHODIMP
 nsDocShell::SetFullscreenAllowed(bool aFullscreenAllowed)
 {
-  if (!nsIDocShell::GetIsBrowserOrApp()) {
+  if (!nsIDocShell::GetIsMozBrowserOrApp()) {
     // Only allow setting of fullscreenAllowed on content/process boundaries.
     // At non-boundaries the fullscreenAllowed attribute is calculated based on
     // whether all enclosing frames have the "mozFullscreenAllowed" attribute
     // set to "true". fullscreenAllowed is set at the process boundaries to
     // propagate the value of the parent's "mozFullscreenAllowed" attribute
     // across process boundaries.
     return NS_ERROR_UNEXPECTED;
   }
@@ -2610,20 +2608,16 @@ nsDocShell::GetDocShellEnumerator(int32_
 
   RefPtr<nsDocShellEnumerator> docShellEnum;
   if (aDirection == ENUMERATE_FORWARDS) {
     docShellEnum = new nsDocShellForwardsEnumerator;
   } else {
     docShellEnum = new nsDocShellBackwardsEnumerator;
   }
 
-  if (!docShellEnum) {
-    return NS_ERROR_OUT_OF_MEMORY;
-  }
-
   nsresult rv = docShellEnum->SetEnumDocShellType(aItemType);
   if (NS_FAILED(rv)) {
     return rv;
   }
 
   rv = docShellEnum->SetEnumerationRootItem((nsIDocShellTreeItem*)this);
   if (NS_FAILED(rv)) {
     return rv;
@@ -3359,17 +3353,17 @@ nsDocShell::SetDocLoaderParent(nsDocLoad
 }
 
 NS_IMETHODIMP
 nsDocShell::GetSameTypeParent(nsIDocShellTreeItem** aParent)
 {
   NS_ENSURE_ARG_POINTER(aParent);
   *aParent = nullptr;
 
-  if (nsIDocShell::GetIsBrowserOrApp()) {
+  if (nsIDocShell::GetIsMozBrowserOrApp()) {
     return NS_OK;
   }
 
   nsCOMPtr<nsIDocShellTreeItem> parent =
     do_QueryInterface(GetAsSupports(mParent));
   if (!parent) {
     return NS_OK;
   }
@@ -3495,17 +3489,18 @@ nsDocShell::CanAccessItem(nsIDocShellTre
 
   nsCOMPtr<nsIDocShell> targetDS = do_QueryInterface(aTargetItem);
   nsCOMPtr<nsIDocShell> accessingDS = do_QueryInterface(aAccessingItem);
   if (!targetDS || !accessingDS) {
     // We must be able to convert both to nsIDocShell.
     return false;
   }
 
-  if (targetDS->GetIsInBrowserElement() != accessingDS->GetIsInBrowserElement() ||
+  if (targetDS->GetIsInIsolatedMozBrowserElement() !=
+        accessingDS->GetIsInIsolatedMozBrowserElement() ||
       targetDS->GetAppId() != accessingDS->GetAppId()) {
     return false;
   }
 
   // A private document can't access a non-private one, and vice versa.
   if (static_cast<nsDocShell*>(targetDS.get())->UsePrivateBrowsing() !=
       static_cast<nsDocShell*>(accessingDS.get())->UsePrivateBrowsing()) {
     return false;
@@ -4010,16 +4005,17 @@ nsDocShell::AddChild(nsIDocShellTreeItem
   }
 
   if (aChild->ItemType() != mItemType) {
     return NS_OK;
   }
 
   aChild->SetTreeOwner(mTreeOwner);
   childDocShell->SetUserContextId(mUserContextId);
+  childDocShell->SetIsInIsolatedMozBrowserElement(mIsInIsolatedMozBrowser);
 
   nsCOMPtr<nsIDocShell> childAsDocShell(do_QueryInterface(aChild));
   if (!childAsDocShell) {
     return NS_OK;
   }
 
   // charset, style-disabling, and zoom will be inherited in SetupNewViewer()
 
@@ -5630,16 +5626,20 @@ nsDocShell::Create()
 
   if (!gAddedPreferencesVarCache) {
     Preferences::AddBoolVarCache(&sUseErrorPages,
                                  "browser.xul.error_pages.enabled",
                                  mUseErrorPages);
     gAddedPreferencesVarCache = true;
   }
 
+  mDisableMetaRefreshWhenInactive =
+    Preferences::GetBool("browser.meta_refresh_when_inactive.disabled",
+                         mDisableMetaRefreshWhenInactive);
+
   mDeviceSizeIsPageSize =
     Preferences::GetBool("docshell.device_size_is_page_size",
                          mDeviceSizeIsPageSize);
 
   nsCOMPtr<nsIObserverService> serv = services::GetObserverService();
   if (serv) {
     const char* msg = mItemType == typeContent ?
       NS_WEBNAVIGATION_CREATE : NS_CHROME_WEBNAVIGATION_CREATE;
@@ -5815,20 +5815,24 @@ nsDocShell::SetPosition(int32_t aX, int3
   }
 
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsDocShell::SetPositionDesktopPix(int32_t aX, int32_t aY)
 {
-  // Added to nsIBaseWindow in bug 1247335;
-  // implement if a use-case is found.
-  NS_ASSERTION(false, "implement me!");
-  return NS_ERROR_NOT_IMPLEMENTED;
+  nsCOMPtr<nsIBaseWindow> ownerWindow(do_QueryInterface(mTreeOwner));
+  if (ownerWindow) {
+    return ownerWindow->SetPositionDesktopPix(aX, aY);
+  }
+
+  double scale = 1.0;
+  GetDevicePixelsPerDesktopPixel(&scale);
+  return SetPosition(NSToIntRound(aX * scale), NSToIntRound(aY * scale));
 }
 
 NS_IMETHODIMP
 nsDocShell::GetPosition(int32_t* aX, int32_t* aY)
 {
   return GetPositionAndSize(aX, aY, nullptr, nullptr);
 }
 
@@ -6119,25 +6123,34 @@ nsDocShell::SetIsActiveInternal(bool aIs
   // children; they handle their state separately.
   nsTObserverArray<nsDocLoader*>::ForwardIterator iter(mChildList);
   while (iter.HasMore()) {
     nsCOMPtr<nsIDocShell> docshell = do_QueryObject(iter.GetNext());
     if (!docshell) {
       continue;
     }
 
-    if (!docshell->GetIsBrowserOrApp()) {
+    if (!docshell->GetIsMozBrowserOrApp()) {
       if (aIsHidden) {
         docshell->SetIsActive(aIsActive);
       } else {
         docshell->SetIsActiveAndForeground(aIsActive);
       }
     }
   }
 
+  // Restart or stop meta refresh timers if necessary
+  if (mDisableMetaRefreshWhenInactive) {
+    if (mIsActive) {
+      ResumeRefreshURIs();
+    } else {
+      SuspendRefreshURIs();
+    }
+  }
+
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsDocShell::GetIsActive(bool* aIsActive)
 {
   *aIsActive = mIsActive;
   return NS_OK;
@@ -6573,37 +6586,35 @@ nsDocShell::RefreshURI(nsIURI* aURI, int
   if (NS_FAILED(rv)) {
     sameURI = false;
   }
   if (!RefreshAttempted(this, aURI, aDelay, sameURI)) {
     return NS_OK;
   }
 
   nsRefreshTimer* refreshTimer = new nsRefreshTimer();
-  NS_ENSURE_TRUE(refreshTimer, NS_ERROR_OUT_OF_MEMORY);
   uint32_t busyFlags = 0;
   GetBusyFlags(&busyFlags);
 
   nsCOMPtr<nsISupports> dataRef = refreshTimer;  // Get the ref count to 1
 
   refreshTimer->mDocShell = this;
   refreshTimer->mURI = aURI;
   refreshTimer->mDelay = aDelay;
   refreshTimer->mRepeat = aRepeat;
   refreshTimer->mMetaRefresh = aMetaRefresh;
 
   if (!mRefreshURIList) {
     NS_ENSURE_SUCCESS(NS_NewISupportsArray(getter_AddRefs(mRefreshURIList)),
                       NS_ERROR_FAILURE);
   }
 
-  if (busyFlags & BUSY_FLAGS_BUSY) {
-    // We are busy loading another page. Don't create the
-    // timer right now. Instead queue up the request and trigger the
-    // timer in EndPageLoad().
+  if (busyFlags & BUSY_FLAGS_BUSY || (!mIsActive && mDisableMetaRefreshWhenInactive)) {
+    // We don't  want to create the timer right now. Instead queue up the request
+    // and trigger the timer in EndPageLoad() or whenever we become active.
     mRefreshURIList->AppendElement(refreshTimer);
   } else {
     // There is no page loading going on right now.  Create the
     // timer and fire it right away.
     nsCOMPtr<nsITimer> timer = do_CreateInstance("@mozilla.org/timer;1");
     NS_ENSURE_TRUE(timer, NS_ERROR_FAILURE);
 
     mRefreshURIList->AppendElement(timer);  // owning timer ref
@@ -7546,17 +7557,18 @@ nsDocShell::EndPageLoad(nsIWebProgress* 
     mLSHE->SetLoadType(nsIDocShellLoadInfo::loadHistory);
 
     // Clear the mLSHE reference to indicate document loading is done one
     // way or another.
     SetHistoryEntry(&mLSHE, nullptr);
   }
   // if there's a refresh header in the channel, this method
   // will set it up for us.
-  RefreshURIFromQueue();
+  if (mIsActive || !mDisableMetaRefreshWhenInactive)
+    RefreshURIFromQueue();
 
   // Test whether this is the top frame or a subframe
   bool isTopFrame = true;
   nsCOMPtr<nsIDocShellTreeItem> targetParentTreeItem;
   rv = GetSameTypeParent(getter_AddRefs(targetParentTreeItem));
   if (NS_SUCCEEDED(rv) && targetParentTreeItem) {
     isTopFrame = false;
   }
@@ -13881,39 +13893,32 @@ nsDocShell::SetUserContextId(uint32_t aU
 
     docshell->SetUserContextId(aUserContextId);
   }
 
   return NS_OK;
 }
 
 /* [infallible] */ NS_IMETHODIMP
-nsDocShell::GetIsBrowserElement(bool* aIsBrowser)
-{
-  *aIsBrowser = (mFrameType == eFrameTypeBrowser);
-  return NS_OK;
-}
-
-/* [infallible] */ NS_IMETHODIMP
 nsDocShell::GetIsApp(bool* aIsApp)
 {
   *aIsApp = (mFrameType == eFrameTypeApp);
   return NS_OK;
 }
 
 /* [infallible] */ NS_IMETHODIMP
-nsDocShell::GetIsBrowserOrApp(bool* aIsBrowserOrApp)
+nsDocShell::GetIsMozBrowserOrApp(bool* aIsMozBrowserOrApp)
 {
   switch (mFrameType) {
     case eFrameTypeRegular:
-      *aIsBrowserOrApp = false;
+      *aIsMozBrowserOrApp = false;
       break;
     case eFrameTypeBrowser:
     case eFrameTypeApp:
-      *aIsBrowserOrApp = true;
+      *aIsMozBrowserOrApp = true;
       break;
   }
 
   return NS_OK;
 }
 
 nsDocShell::FrameType
 nsDocShell::GetInheritedFrameType()
@@ -13929,32 +13934,52 @@ nsDocShell::GetInheritedFrameType()
   if (!parent) {
     return eFrameTypeRegular;
   }
 
   return static_cast<nsDocShell*>(parent.get())->GetInheritedFrameType();
 }
 
 /* [infallible] */ NS_IMETHODIMP
-nsDocShell::GetIsInBrowserElement(bool* aIsInBrowserElement)
-{
-  *aIsInBrowserElement = (GetInheritedFrameType() == eFrameTypeBrowser);
+nsDocShell::GetIsIsolatedMozBrowserElement(bool* aIsIsolatedMozBrowserElement)
+{
+  bool result = mFrameType == eFrameTypeBrowser && mIsInIsolatedMozBrowser;
+  *aIsIsolatedMozBrowserElement = result;
   return NS_OK;
 }
 
 /* [infallible] */ NS_IMETHODIMP
-nsDocShell::GetIsInBrowserOrApp(bool* aIsInBrowserOrApp)
+nsDocShell::GetIsInIsolatedMozBrowserElement(bool* aIsInIsolatedMozBrowserElement)
+{
+  MOZ_ASSERT(!mIsInIsolatedMozBrowser ||
+             (GetInheritedFrameType() == eFrameTypeBrowser),
+             "Isolated mozbrowser should only be true inside browser frames");
+  bool result = (GetInheritedFrameType() == eFrameTypeBrowser) &&
+                mIsInIsolatedMozBrowser;
+  *aIsInIsolatedMozBrowserElement = result;
+  return NS_OK;
+}
+
+/* [infallible] */ NS_IMETHODIMP
+nsDocShell::SetIsInIsolatedMozBrowserElement(bool aIsInIsolatedMozBrowserElement)
+{
+  mIsInIsolatedMozBrowser = aIsInIsolatedMozBrowserElement;
+  return NS_OK;
+}
+
+/* [infallible] */ NS_IMETHODIMP
+nsDocShell::GetIsInMozBrowserOrApp(bool* aIsInMozBrowserOrApp)
 {
   switch (GetInheritedFrameType()) {
     case eFrameTypeRegular:
-      *aIsInBrowserOrApp = false;
+      *aIsInMozBrowserOrApp = false;
       break;
     case eFrameTypeBrowser:
     case eFrameTypeApp:
-      *aIsInBrowserOrApp = true;
+      *aIsInMozBrowserOrApp = true;
       break;
   }
 
   return NS_OK;
 }
 
 /* [infallible] */ NS_IMETHODIMP
 nsDocShell::GetAppId(uint32_t* aAppId)
@@ -13990,20 +14015,17 @@ nsDocShell::GetOriginAttributes()
     attrs.mSignedPkg = mSignedPkg;
   }
 
   if (mOwnOrContainingAppId != nsIScriptSecurityManager::UNKNOWN_APP_ID) {
     attrs.mAppId = mOwnOrContainingAppId;
   }
 
   attrs.mUserContextId = mUserContextId;
-
-  if (mFrameType == eFrameTypeBrowser) {
-    attrs.mInBrowser = true;
-  }
+  attrs.mInIsolatedMozBrowser = mIsInIsolatedMozBrowser;
 
   return attrs;
 }
 
 NS_IMETHODIMP
 nsDocShell::GetOriginAttributes(JS::MutableHandle<JS::Value> aVal)
 {
   JSContext* cx = nsContentUtils::GetCurrentJSContext();

--- a/docshell/base/nsDocShell.h
+++ b/docshell/base/nsDocShell.h
@@ -933,16 +933,17 @@ protected:
   bool mAllowContentRetargetingOnChildren;
   bool mCreatingDocument; // (should be) debugging only
   bool mUseErrorPages;
   bool mObserveErrorPages;
   bool mAllowAuth;
   bool mAllowKeywordFixup;
   bool mIsOffScreenBrowser;
   bool mIsActive;
+  bool mDisableMetaRefreshWhenInactive;
   bool mIsPrerendered;
   bool mIsAppTab;
   bool mUseGlobalHistory;
   bool mInPrivateBrowsing;
   bool mUseRemoteTabs;
   bool mDeviceSizeIsPageSize;
   bool mWindowDraggingAllowed;
   bool mInFrameSwap;
@@ -995,16 +996,19 @@ protected:
   // This flag means that mTiming has been initialized but nulled out.
   // We will check the innerWin's timing before creating a new one
   // in MaybeInitTiming()
   bool mBlankTiming;
 
   // Are we a regular frame, a browser frame, or an app frame?
   FrameType mFrameType;
 
+  // Whether we are in an isolated mozbrowser frame.
+  bool mIsInIsolatedMozBrowser;
+
   // We only expect mOwnOrContainingAppId to be something other than
   // UNKNOWN_APP_ID if mFrameType != eFrameTypeRegular. For vanilla iframes
   // inside an app, we'll retrieve the containing app-id by walking up the
   // docshell hierarchy.
   //
   // (This needs to be the docshell's own /or containing/ app id because the
   // containing app frame might be in another process, in which case we won't
   // find it by walking up the docshell hierarchy.)

--- a/docshell/base/nsIDocShell.idl
+++ b/docshell/base/nsIDocShell.idl
@@ -759,53 +759,64 @@ interface nsIDocShell : nsIDocShellTreeI
 
   /**
    * Notify all attached observers that the scroll position of some element
    * has changed.
    */
   [noscript] void notifyScrollObservers();
 
   /**
-   * Returns true if this docshell corresponds to an <iframe mozbrowser>.
-   * (<iframe mozapp mozbrowser> is not considered a browser.)
-   */
-  [infallible] readonly attribute boolean isBrowserElement;
-
-  /**
    * Returns true iff the docshell corresponds to an <iframe mozapp>.
    */
   [infallible] readonly attribute boolean isApp;
 
   /**
-   * Returns isBrowserElement || isApp.
+   * Returns true if this docshell corresponds to an <iframe mozbrowser> or
+   * <iframe mozapp>.  <xul:browser> returns false here.
    */
-  [infallible] readonly attribute boolean isBrowserOrApp;
+  [infallible] readonly attribute boolean isMozBrowserOrApp;
 
   /**
-   * Returns true if this docshell corresponds to an <iframe mozbrowser> or if
-   * the docshell is contained in an <iframe mozbrowser>.  (<iframe mozapp
-   * mozbrowser> does not count as a browser.)
+   * Returns true if this docshell corresponds to an isolated <iframe
+   * mozbrowser>.
+   *
+   * <iframe mozbrowser mozapp> and <xul:browser> are not considered to be
+   * mozbrowser elements.  <iframe mozbrowser noisolation> does not count as
+   * isolated since isolation is disabled.  Isolation can only be disabled if
+   * the containing document is chrome.
+   */
+  [infallible] readonly attribute boolean isIsolatedMozBrowserElement;
+
+  /**
+   * Returns true if this docshell corresponds to an isolated <iframe
+   * mozbrowser> or if the docshell is contained in an isolated <iframe
+   * mozbrowser>.
+   *
+   * <iframe mozbrowser mozapp> and <xul:browser> are not considered to be
+   * mozbrowser elements.  <iframe mozbrowser noisolation> does not count as
+   * isolated since isolation is disabled.  Isolation can only be disabled if
+   * the containing document is chrome.
    *
    * Our notion here of "contained in" means: Walk up the docshell hierarchy in
    * this process until we hit an <iframe mozapp> or <iframe mozbrowser> (or
    * until the hierarchy ends).  Return true iff the docshell we stopped on has
-   * isBrowserElement == true.
+   * isIsolatedMozBrowserElement == true.
    */
-  [infallible] readonly attribute boolean isInBrowserElement;
+  [infallible] attribute boolean isInIsolatedMozBrowserElement;
 
   /**
    * Returns true if this docshell corresponds to an <iframe mozbrowser> or
    * <iframe mozapp>, or if this docshell is contained in an <iframe mozbrowser>
-   * or <iframe mozapp>.
+   * or <iframe mozapp>.  <xul:browser> returns false here.
    *
    * To compute this value, we walk up the docshell hierarchy.  If we encounter
-   * a docshell with isBrowserElement or isApp before we hit the end of the
-   * hierarchy, we return true.  Otherwise, we return false.
+   * a docshell with isMozBrowserOrApp before we hit the end of the hierarchy,
+   * we return true.  Otherwise, we return false.
    */
-  [infallible] readonly attribute boolean isInBrowserOrApp;
+  [infallible] readonly attribute boolean isInMozBrowserOrApp;
 
    /**
     * Indicate that this docshell corresponds to an app with the given app id.
     *
     * You may pass NO_APP_ID or UNKNOWN_APP_ID for containingAppId.  If you
     * pass NO_APP_ID, then this docshell will return NO_APP_ID for appId.  If
     * you pass UNKNOWN_APP_ID, then this docshell will search its hiearchy for
     * an app frame and use that frame's appId.

--- a/docshell/base/nsILoadContext.idl
+++ b/docshell/base/nsILoadContext.idl
@@ -111,19 +111,23 @@ interface nsILoadContext : nsISupports
   [noscript] void SetPrivateBrowsing(in boolean aInPrivateBrowsing);
 
   /**
    * Set the remote tabs state of the load context, meant to be used internally.
    */
   [noscript] void SetRemoteTabs(in boolean aUseRemoteTabs);
 
   /**
-   * Returns true iff the load is occurring inside a browser element.
+   * Returns true iff the load is occurring inside an isolated mozbrowser
+   * element. <iframe mozbrowser mozapp> and <xul:browser> are not considered to
+   * be mozbrowser elements.  <iframe mozbrowser noisolation> does not count as
+   * isolated since isolation is disabled.  Isolation can only be disabled if
+   * the containing document is chrome.
    */
-  readonly attribute boolean isInBrowserElement;
+  readonly attribute boolean isInIsolatedMozBrowserElement;
 
   /**
    * Returns the app id of the app the load is occurring is in. Returns
    * nsIScriptSecurityManager::NO_APP_ID if the load is not part of an app.
    */
   readonly attribute unsigned long appId;
 
   /**

--- a/dom/animation/AnimationTimeline.h
+++ b/dom/animation/AnimationTimeline.h
@@ -86,16 +86,27 @@ public:
   /**
    * Inform this timeline that |aAnimation| which is or was observing the
    * timeline, has been updated. This serves as both the means to associate
    * AND disassociate animations with a timeline. The timeline itself will
    * determine if it needs to begin, continue or stop tracking this animation.
    */
   virtual void NotifyAnimationUpdated(Animation& aAnimation);
 
+  /**
+   * Returns true if any CSS animations, CSS transitions or Web animations are
+   * currently associated with this timeline.  As soon as an animation is
+   * applied to an element it is associated with the timeline even if it has a
+   * delayed start, so this includes animations that may not be active for some
+   * time.
+   */
+  bool HasAnimations() const {
+    return !mAnimations.IsEmpty();
+  }
+
   void RemoveAnimation(Animation* aAnimation);
 
 protected:
   nsCOMPtr<nsIGlobalObject> mWindow;
 
   // Animations observing this timeline
   //
   // We store them in (a) a hashset for quick lookup, and (b) an array

--- a/dom/apps/AppsService.js
+++ b/dom/apps/AppsService.js
@@ -101,16 +101,20 @@ AppsService.prototype = {
     return DOMApplicationRegistry.getCoreAppsBasePath();
   },
 
   getWebAppsBasePath: function getWebAppsBasePath() {
     debug("getWebAppsBasePath()");
     return DOMApplicationRegistry.getWebAppsBasePath();
   },
 
+  areAnyAppsInstalled: function() {
+    return DOMApplicationRegistry.areAnyAppsInstalled();
+  },
+
   getAppInfo: function getAppInfo(aAppId) {
     debug("getAppInfo()");
     return DOMApplicationRegistry.getAppInfo(aAppId);
   },
 
   getRedirect: function getRedirect(aLocalId, aURI) {
     debug("getRedirect for " + aLocalId + " " + aURI.spec);
     if (this.isInvalidId(aLocalId)) {

--- a/dom/apps/AppsServiceChild.jsm
+++ b/dom/apps/AppsServiceChild.jsm
@@ -407,16 +407,20 @@ this.DOMApplicationRegistry = {
     return null;
   },
 
   getWebAppsBasePath: function getWebAppsBasePath() {
     debug("getWebAppsBasePath() not yet supported on child!");
     return null;
   },
 
+  areAnyAppsInstalled: function() {
+    return AppsUtils.areAnyAppsInstalled(this.webapps);
+  },
+
   getAppInfo: function getAppInfo(aAppId) {
     return AppsUtils.getAppInfo(this.webapps, aAppId);
   },
 
   updateDataStoreEntriesFromLocalId: function(aLocalId) {
     debug("updateDataStoreEntriesFromLocalId() not yet supported on child!");
   }
 }

--- a/dom/apps/AppsUtils.jsm
+++ b/dom/apps/AppsUtils.jsm
@@ -144,26 +144,27 @@ function _setAppProperties(aObj, aApp) {
 this.AppsUtils = {
   // Clones a app, without the manifest.
   cloneAppObject: function(aApp) {
     let obj = {};
     _setAppProperties(obj, aApp);
     return obj;
   },
 
-  // Creates a nsILoadContext object with a given appId and isBrowser flag.
-  createLoadContext: function createLoadContext(aAppId, aIsBrowser) {
+  // Creates a nsILoadContext object with a given appId and inIsolatedMozBrowser
+  // flag.
+  createLoadContext: function createLoadContext(aAppId, aInIsolatedMozBrowser) {
     return {
        associatedWindow: null,
        topWindow : null,
        appId: aAppId,
-       isInBrowserElement: aIsBrowser,
+       isInIsolatedMozBrowserElement: aInIsolatedMozBrowser,
        originAttributes: {
          appId: aAppId,
-         inBrowser: aIsBrowser
+         inIsolatedMozBrowser: aInIsolatedMozBrowser
        },
        usePrivateBrowsing: false,
        isContent: false,
 
        isAppOfType: function(appType) {
          throw Cr.NS_ERROR_NOT_IMPLEMENTED;
        },
 
@@ -339,16 +340,20 @@ this.AppsUtils = {
       if (app.localId == aLocalId) {
         return app.manifestURL;
       }
     }
 
     return "";
   },
 
+  areAnyAppsInstalled: function(aApps) {
+    return Object.getOwnPropertyNames(aApps).length > 0;
+  },
+
   getCoreAppsBasePath: function getCoreAppsBasePath() {
     debug("getCoreAppsBasePath()");
     try {
       return FileUtils.getDir("coreAppsDir", ["webapps"], false).path;
     } catch(e) {
       return null;
     }
   },

--- a/dom/apps/Webapps.js
+++ b/dom/apps/Webapps.js
@@ -178,17 +178,17 @@ WebappsRegistry.prototype = {
                     categories: categories
                   },
 
              from: installURL,
              oid: this._id,
              topId: this._topId,
              requestID: requestID,
              appId: principal.appId,
-             isBrowser: principal.isInBrowserElement,
+             isBrowser: principal.isInIsolatedMozBrowserElement,
              isPackage: isPackage
            };
   },
 
   // mozIDOMApplicationRegistry implementation
 
   install: function(aURL, aParams) {
     let request = this.createRequest();

--- a/dom/apps/Webapps.jsm
+++ b/dom/apps/Webapps.jsm
@@ -3531,20 +3531,20 @@ this.DOMApplicationRegistry = {
           lastProgressTime = now;
           this._saveApps();
         }
       }).bind(this),
       onStatus: function(aRequest, aContext, aStatus, aStatusArg) { },
 
       // nsILoadContext
       appId: aOldApp.installerAppId,
-      isInBrowserElement: aOldApp.installerIsBrowser,
+      isInIsolatedMozBrowserElement: aOldApp.installerIsBrowser,
       originAttributes: {
         appId: aOldApp.installerAppId,
-        inBrowser: aOldApp.installerIsBrowser
+        inIsolatedMozBrowser: aOldApp.installerIsBrowser
       },
       usePrivateBrowsing: false,
       isContent: false,
       associatedWindow: null,
       topWindow : null,
       isAppOfType: function(appType) {
         throw Cr.NS_ERROR_NOT_IMPLEMENTED;
       }
@@ -4794,16 +4794,20 @@ this.DOMApplicationRegistry = {
   getCoreAppsBasePath: function() {
     return AppsUtils.getCoreAppsBasePath();
   },
 
   getWebAppsBasePath: function() {
     return OS.Path.dirname(this.appsFile);
   },
 
+  areAnyAppsInstalled: function() {
+    return AppsUtils.areAnyAppsInstalled(this.webapps);
+  },
+
   updateDataStoreEntriesFromLocalId: function(aLocalId) {
     let app = appsService.getAppByLocalId(aLocalId);
     if (app) {
       this.updateDataStoreForApp(app.id);
     }
   },
 
   _isLaunchable: function(aApp) {
@@ -4897,17 +4901,17 @@ this.DOMApplicationRegistry = {
     };
     this._clearOriginData(appId, browserOnly);
     this._notifyCategoryAndObservers(subject, "webapps-clear-data", null, msg);
   },
 
   _clearOriginData: function(appId, browserOnly) {
     let attributes = {appId: appId};
     if (browserOnly) {
-      attributes.inBrowser = true;
+      attributes.inIsolatedMozBrowser = true;
     }
     this._notifyCategoryAndObservers(null, "clear-origin-data", JSON.stringify(attributes));
   }
 };
 
 /**
  * Appcache download observer
  */

--- a/dom/apps/tests/unit/test_moziapplication.js
+++ b/dom/apps/tests/unit/test_moziapplication.js
@@ -48,16 +48,16 @@ add_test(() => {
                  "app[" + key + "] should be equal to mozapp[" + key + "]");
   });
 
   Assert.ok(mozapp.principal, "app principal should exist");
   let expectedPrincipalOrigin = app.origin + "^appId=" + app.localId;
   Assert.equal(mozapp.principal.origin, expectedPrincipalOrigin,
                "app principal origin ok");
   Assert.equal(mozapp.principal.appId, app.localId, "app principal appId ok");
-  Assert.equal(mozapp.principal.isInBrowserElement, false,
-               "app principal isInBrowserElement ok");
+  Assert.equal(mozapp.principal.isInIsolatedMozBrowserElement, false,
+               "app principal isInIsolatedMozBrowserElement ok");
   run_next_test();
 });
 
 function run_test() {
   run_next_test();
 }

--- a/dom/base/ChromeUtils.cpp
+++ b/dom/base/ChromeUtils.cpp
@@ -103,15 +103,15 @@ ChromeUtils::CreateOriginAttributesFromD
 
 /* static */ bool
 ChromeUtils::IsOriginAttributesEqual(dom::GlobalObject& aGlobal,
                                      const dom::OriginAttributesDictionary& aA,
                                      const dom::OriginAttributesDictionary& aB)
 {
   return aA.mAddonId == aB.mAddonId &&
          aA.mAppId == aB.mAppId &&
-         aA.mInBrowser == aB.mInBrowser &&
+         aA.mInIsolatedMozBrowser == aB.mInIsolatedMozBrowser &&
          aA.mSignedPkg == aB.mSignedPkg &&
          aA.mUserContextId == aB.mUserContextId;
 }
 
 } // namespace dom
 } // namespace mozilla

--- a/dom/base/PerformanceObserver.cpp
+++ b/dom/base/PerformanceObserver.cpp
@@ -130,38 +130,39 @@ PerformanceObserver::QueueEntry(Performa
   aEntry->GetEntryType(entryType);
   if (!mEntryTypes.Contains<nsString>(entryType)) {
     return;
   }
 
   mQueuedEntries.AppendElement(aEntry);
 }
 
-static nsString sValidTypeNames[7] = {
-  NS_LITERAL_STRING("composite"),
-  NS_LITERAL_STRING("mark"),
-  NS_LITERAL_STRING("measure"),
-  NS_LITERAL_STRING("navigation"),
-  NS_LITERAL_STRING("render"),
-  NS_LITERAL_STRING("resource"),
-  NS_LITERAL_STRING("server")
+static const char16_t* sValidTypeNames[7] = {
+  MOZ_UTF16("composite"),
+  MOZ_UTF16("mark"),
+  MOZ_UTF16("measure"),
+  MOZ_UTF16("navigation"),
+  MOZ_UTF16("render"),
+  MOZ_UTF16("resource"),
+  MOZ_UTF16("server")
 };
 
 void
 PerformanceObserver::Observe(const PerformanceObserverInit& aOptions,
                              ErrorResult& aRv)
 {
   if (aOptions.mEntryTypes.IsEmpty()) {
     aRv.Throw(NS_ERROR_DOM_TYPE_ERR);
     return;
   }
 
   nsTArray<nsString> validEntryTypes;
 
-  for (const nsString& validTypeName : sValidTypeNames) {
+  for (const char16_t* name : sValidTypeNames) {
+    nsDependentString validTypeName(name);
     if (aOptions.mEntryTypes.Contains<nsString>(validTypeName) &&
         !validEntryTypes.Contains<nsString>(validTypeName)) {
       validEntryTypes.AppendElement(validTypeName);
     }
   }
 
   if (validEntryTypes.IsEmpty()) {
     aRv.Throw(NS_ERROR_DOM_TYPE_ERR);

--- a/dom/base/ScriptSettings.cpp
+++ b/dom/base/ScriptSettings.cpp
@@ -344,19 +344,20 @@ AutoJSAPI::InitInternal(JSObject* aGloba
     // be necessary.
     JS::Rooted<JSObject*> global(JS_GetRuntime(aCx), aGlobal);
     mCxPusher.emplace(mCx);
     mAutoNullableCompartment.emplace(mCx, global);
   } else {
     mAutoNullableCompartment.emplace(mCx, aGlobal);
   }
 
+  JSRuntime* rt = JS_GetRuntime(aCx);
+  mOldErrorReporter.emplace(JS_GetErrorReporter(rt));
+
   if (aIsMainThread) {
-    JSRuntime* rt = JS_GetRuntime(aCx);
-    mOldErrorReporter.emplace(JS_GetErrorReporter(rt));
     JS_SetErrorReporter(rt, xpc::SystemErrorReporter);
   }
 }
 
 AutoJSAPI::AutoJSAPI(nsIGlobalObject* aGlobalObject,
                      bool aIsMainThread,
                      JSContext* aCx)
   : mOwnErrorReporting(false)
@@ -460,18 +461,31 @@ AutoJSAPI::InitWithLegacyErrorReporting(
 // reports to the JSErrorReporter as soon as they are generated. These go
 // directly to the console, so we can handle them easily here.
 //
 // Eventually, SpiderMonkey will have a special-purpose callback for warnings
 // only.
 void
 WarningOnlyErrorReporter(JSContext* aCx, const char* aMessage, JSErrorReport* aRep)
 {
-  MOZ_ASSERT(NS_IsMainThread());
   MOZ_ASSERT(JSREPORT_IS_WARNING(aRep->flags));
+  if (!NS_IsMainThread()) {
+    // Reporting a warning on workers is a bit complicated because we have to
+    // climb our parent chain until we get to the main thread.  So go ahead and
+    // just go through the worker ReportError codepath here.
+    //
+    // That said, it feels like we should be able to short-circuit things a bit
+    // here by posting an appropriate runnable to the main thread directly...
+    // Worth looking into sometime.
+    workers::WorkerPrivate* worker = workers::GetWorkerPrivateFromContext(aCx);
+    MOZ_ASSERT(worker);
+
+    worker->ReportError(aCx, aMessage, aRep);
+    return;
+  }
 
   RefPtr<xpc::ErrorReport> xpcReport = new xpc::ErrorReport();
   nsGlobalWindow* win = xpc::CurrentWindowOrNull(aCx);
   xpcReport->Init(aRep, aMessage, nsContentUtils::IsCallerChrome(),
                   win ? win->AsInner()->WindowID() : 0);
   xpcReport->LogToConsole();
 }
 
@@ -479,23 +493,17 @@ void
 AutoJSAPI::TakeOwnershipOfErrorReporting()
 {
   MOZ_ASSERT(!mOwnErrorReporting);
   mOwnErrorReporting = true;
 
   JSRuntime *rt = JS_GetRuntime(cx());
   mOldAutoJSAPIOwnsErrorReporting = JS::ContextOptionsRef(cx()).autoJSAPIOwnsErrorReporting();
   JS::ContextOptionsRef(cx()).setAutoJSAPIOwnsErrorReporting(true);
-  // Workers have their own error reporting mechanism which deals with warnings
-  // as well, so don't change the worker error reporter for now.  Once we switch
-  // all of workers to TakeOwnershipOfErrorReporting(), we will just make the
-  // default worker error reporter assert that it only sees warnings.
-  if (mIsMainThread) {
-    JS_SetErrorReporter(rt, WarningOnlyErrorReporter);
-  }
+  JS_SetErrorReporter(rt, WarningOnlyErrorReporter);
 }
 
 void
 AutoJSAPI::ReportException()
 {
   MOZ_ASSERT(OwnsErrorReporting(), "This is not our exception to report!");
   if (!HasException()) {
     return;
@@ -543,16 +551,17 @@ AutoJSAPI::ReportException()
       // to get hold of it.  After we invoke ReportError, clear the exception on
       // cx(), just in case ReportError didn't.
       JS_SetPendingException(cx(), exn);
       worker->ReportError(cx(), jsReport.message(), jsReport.report());
       ClearException();
     }
   } else {
     NS_WARNING("OOMed while acquiring uncaught exception from JSAPI");
+    ClearException();
   }
 }
 
 bool
 AutoJSAPI::PeekException(JS::MutableHandle<JS::Value> aVal)
 {
   MOZ_ASSERT_IF(mIsMainThread, CxPusherIsStackTop());
   MOZ_ASSERT(HasException());

--- a/dom/base/nsFrameLoader.cpp
+++ b/dom/base/nsFrameLoader.cpp
@@ -417,17 +417,17 @@ nsFrameLoader::ReallyStartLoadingInterna
     }
   }
   loadInfo->SetReferrerPolicy(referrerPolicy);
 
   // Default flags:
   int32_t flags = nsIWebNavigation::LOAD_FLAGS_NONE;
 
   // Flags for browser frame:
-  if (OwnerIsBrowserFrame()) {
+  if (OwnerIsMozBrowserFrame()) {
     flags = nsIWebNavigation::LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP |
             nsIWebNavigation::LOAD_FLAGS_DISALLOW_INHERIT_OWNER;
   }
 
   // Kick off the load...
   bool tmpState = mNeedsAsyncDestroy;
   mNeedsAsyncDestroy = true;
   nsCOMPtr<nsIURI> uriToLoad = mURIToLoad;
@@ -1195,18 +1195,18 @@ nsFrameLoader::SwapWithOtherLoader(nsFra
   NS_ASSERTION(otherDoc == otherParentDocument, "Unexpected parent document");
 
   nsIPresShell* ourShell = ourDoc->GetShell();
   nsIPresShell* otherShell = otherDoc->GetShell();
   if (!ourShell || !otherShell) {
     return NS_ERROR_NOT_IMPLEMENTED;
   }
 
-  if (ourDocshell->GetIsBrowserElement() !=
-      otherDocshell->GetIsBrowserElement() ||
+  if (ourDocshell->GetIsIsolatedMozBrowserElement() !=
+      otherDocshell->GetIsIsolatedMozBrowserElement() ||
       ourDocshell->GetIsApp() != otherDocshell->GetIsApp()) {
       return NS_ERROR_NOT_IMPLEMENTED;
   }
 
   if (mInSwap || aOther->mInSwap) {
     return NS_ERROR_NOT_IMPLEMENTED;
   }
   AutoResetInFrameSwap autoFrameSwap(this, aOther, ourDocshell, otherDocshell,
@@ -1572,27 +1572,27 @@ nsFrameLoader::SetOwnerContent(Element* 
   if (RenderFrameParent* rfp = GetCurrentRenderFrame()) {
     rfp->OwnerContentChanged(aContent);
   }
 
   ResetPermissionManagerStatus();
 }
 
 bool
-nsFrameLoader::OwnerIsBrowserOrAppFrame()
+nsFrameLoader::OwnerIsMozBrowserOrAppFrame()
 {
   nsCOMPtr<nsIMozBrowserFrame> browserFrame = do_QueryInterface(mOwnerContent);
   return browserFrame ? browserFrame->GetReallyIsBrowserOrApp() : false;
 }
 
 // The xpcom getter version
 NS_IMETHODIMP
-nsFrameLoader::GetOwnerIsBrowserOrAppFrame(bool* aResult)
+nsFrameLoader::GetOwnerIsMozBrowserOrAppFrame(bool* aResult)
 {
-  *aResult = OwnerIsBrowserOrAppFrame();
+  *aResult = OwnerIsMozBrowserOrAppFrame();
   return NS_OK;
 }
 
 bool
 nsFrameLoader::OwnerIsWidget()
 {
   nsCOMPtr<nsIMozBrowserFrame> browserFrame = do_QueryInterface(mOwnerContent);
   return browserFrame ? browserFrame->GetReallyIsWidget() : false;
@@ -1610,19 +1610,76 @@ nsFrameLoader::GetOwnerIsWidget(bool* aR
 bool
 nsFrameLoader::OwnerIsAppFrame()
 {
   nsCOMPtr<nsIMozBrowserFrame> browserFrame = do_QueryInterface(mOwnerContent);
   return browserFrame ? browserFrame->GetReallyIsApp() : false;
 }
 
 bool
-nsFrameLoader::OwnerIsBrowserFrame()
+nsFrameLoader::OwnerIsMozBrowserFrame()
+{
+  return OwnerIsMozBrowserOrAppFrame() && !OwnerIsAppFrame();
+}
+
+bool
+nsFrameLoader::OwnerIsIsolatedMozBrowserFrame()
 {
-  return OwnerIsBrowserOrAppFrame() && !OwnerIsAppFrame();
+  nsCOMPtr<nsIMozBrowserFrame> browserFrame = do_QueryInterface(mOwnerContent);
+  if (!browserFrame) {
+    return false;
+  }
+
+  if (!OwnerIsMozBrowserFrame()) {
+    return false;
+  }
+
+  bool isolated = browserFrame->GetIsolated();
+  if (isolated) {
+    return true;
+  }
+
+  // After bug 1238160, which allows isolation to be disabled on mozbrowser
+  // frames, we no longer have a way to tell from the principal alone if
+  // something "is a mozbrowser".  Instead, we now only know "is an isolated
+  // mozbrowser".  The following code paths would return invalid results if it
+  // were possible to have apps *and* isolation could be disabled:
+  //   * CheckPermission in AppProcessChecker.cpp
+  //   * nsScriptSecurityManager::AppStatusForPrincipal
+  //   * init() in SystemMessageManager.js
+  // Currently, desktop is the only platform where we intend to disable
+  // isolation on a browser frame, so non-desktop should be able to assume that
+  // inIsolatedMozBrowser is true for all mozbrowser frames.  To enforce these
+  // assumptions, we assert that there are no apps installed if we have tried
+  // to disable isolation.
+  nsCOMPtr<nsIAppsService> appsService = do_GetService(APPS_SERVICE_CONTRACTID);
+  if (!appsService) {
+    // If the apps service is not present, we assume this means there can't be
+    // any apps at all, so there is no problem.
+    return false;
+  }
+  bool appsInstalled;
+  nsresult rv = appsService->AreAnyAppsInstalled(&appsInstalled);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    // The apps service exists, but it threw an error when checking if there are
+    // any apps, so we don't know if we have them or not.
+    return false;
+  }
+#ifdef MOZ_B2G
+  MOZ_RELEASE_ASSERT(!appsInstalled,
+                     "Disabling mozbrowser isolation is not currently "
+                     "allowed when apps are installed.");
+#else
+  if (appsInstalled) {
+    NS_WARNING("Disabling mozbrowser isolation is not currently allowed when "
+               "apps are installed.");
+  }
+#endif
+
+  return false;
 }
 
 void
 nsFrameLoader::GetOwnerAppManifestURL(nsAString& aOut)
 {
   aOut.Truncate();
   nsCOMPtr<nsIMozBrowserFrame> browserFrame = do_QueryInterface(mOwnerContent);
   if (browserFrame) {
@@ -1687,25 +1744,25 @@ nsFrameLoader::ShouldUseRemoteProcess()
   if (XRE_IsContentProcess() &&
       !(PR_GetEnv("MOZ_NESTED_OOP_TABS") ||
         Preferences::GetBool("dom.ipc.tabs.nested.enabled", false))) {
     return false;
   }
 
   // If we're an <iframe mozbrowser> and we don't have a "remote" attribute,
   // fall back to the default.
-  if (OwnerIsBrowserOrAppFrame() &&
+  if (OwnerIsMozBrowserOrAppFrame() &&
       !mOwnerContent->HasAttr(kNameSpaceID_None, nsGkAtoms::Remote)) {
 
     return Preferences::GetBool("dom.ipc.browser_frames.oop_by_default", false);
   }
 
   // Otherwise, we're remote if we have "remote=true" and we're either a
   // browser frame or a XUL element.
-  return (OwnerIsBrowserOrAppFrame() ||
+  return (OwnerIsMozBrowserOrAppFrame() ||
           mOwnerContent->GetNameSpaceID() == kNameSpaceID_XUL) &&
          mOwnerContent->AttrValueIs(kNameSpaceID_None,
                                     nsGkAtoms::Remote,
                                     nsGkAtoms::_true,
                                     eCaseMatters);
 }
 
 bool
@@ -1878,42 +1935,43 @@ nsFrameLoader::MaybeCreateDocShell()
     NS_ENSURE_SUCCESS(rv, rv);
 
     nsCOMPtr<nsIWebNavigation> webNav(do_QueryInterface(mDocShell));
     webNav->SetSessionHistory(sessionHistory);
   }
 
   if (OwnerIsAppFrame()) {
     // You can't be both an app and a browser frame.
-    MOZ_ASSERT(!OwnerIsBrowserFrame());
+    MOZ_ASSERT(!OwnerIsMozBrowserFrame());
 
     nsCOMPtr<mozIApplication> ownApp = GetOwnApp();
     MOZ_ASSERT(ownApp);
     uint32_t ownAppId = nsIScriptSecurityManager::NO_APP_ID;
     if (ownApp) {
       NS_ENSURE_SUCCESS(ownApp->GetLocalId(&ownAppId), NS_ERROR_FAILURE);
     }
 
     mDocShell->SetIsApp(ownAppId);
   }
 
-  if (OwnerIsBrowserFrame()) {
+  if (OwnerIsMozBrowserFrame()) {
     // You can't be both a browser and an app frame.
     MOZ_ASSERT(!OwnerIsAppFrame());
 
     nsCOMPtr<mozIApplication> containingApp = GetContainingApp();
     uint32_t containingAppId = nsIScriptSecurityManager::NO_APP_ID;
     if (containingApp) {
       NS_ENSURE_SUCCESS(containingApp->GetLocalId(&containingAppId),
                         NS_ERROR_FAILURE);
     }
     mDocShell->SetIsBrowserInsideApp(containingAppId);
+    mDocShell->SetIsInIsolatedMozBrowserElement(OwnerIsIsolatedMozBrowserFrame());
   }
 
-  if (OwnerIsBrowserOrAppFrame()) {
+  if (OwnerIsMozBrowserOrAppFrame()) {
     // For inproc frames, set the docshell properties.
     nsCOMPtr<nsIDocShellTreeItem> item = do_GetInterface(docShell);
     nsAutoString name;
     if (mOwnerContent->GetAttr(kNameSpaceID_None, nsGkAtoms::name, name)) {
       item->SetName(name);
     }
     mDocShell->SetFullscreenAllowed(
       mOwnerContent->HasAttr(kNameSpaceID_None, nsGkAtoms::allowfullscreen) ||
@@ -2244,17 +2302,17 @@ nsFrameLoader::TryRemoteBrowser()
 
   if (openingTab &&
       openingTab->Manager() &&
       openingTab->Manager()->IsContentParent()) {
     openerContentParent = openingTab->Manager()->AsContentParent();
   }
 
   // <iframe mozbrowser> gets to skip these checks.
-  if (!OwnerIsBrowserOrAppFrame()) {
+  if (!OwnerIsMozBrowserOrAppFrame()) {
     if (parentDocShell->ItemType() != nsIDocShellTreeItem::typeChrome) {
       return false;
     }
 
     if (!mOwnerContent->IsXULElement()) {
       return false;
     }
 
@@ -2561,17 +2619,17 @@ nsFrameLoader::EnsureMessageManager()
 {
   NS_ENSURE_STATE(mOwnerContent);
 
   if (mMessageManager) {
     return NS_OK;
   }
 
   if (!mIsTopLevelContent &&
-      !OwnerIsBrowserOrAppFrame() &&
+      !OwnerIsMozBrowserOrAppFrame() &&
       !IsRemoteFrame() &&
       !(mOwnerContent->IsXULElement() &&
         mOwnerContent->AttrValueIs(kNameSpaceID_None,
                                    nsGkAtoms::forcemessagemanager,
                                    nsGkAtoms::_true, eCaseMatters))) {
     return NS_OK;
   }
 
@@ -2667,17 +2725,17 @@ nsFrameLoader::SwapRemoteBrowser(nsITabP
   RefPtr<TabParent> newParent = TabParent::GetFrom(aTabParent);
   if (!newParent || !mRemoteBrowser) {
     return NS_ERROR_DOM_INVALID_STATE_ERR;
   }
   if (!IsRemoteFrame()) {
     NS_WARNING("Switching from in-process to out-of-process is not supported.");
     return NS_ERROR_NOT_IMPLEMENTED;
   }
-  if (!OwnerIsBrowserOrAppFrame()) {
+  if (!OwnerIsMozBrowserOrAppFrame()) {
     NS_WARNING("Switching process for non-mozbrowser/app frame is not supported.");
     return NS_ERROR_NOT_IMPLEMENTED;
   }
   if (newParent == mRemoteBrowser) {
     return NS_OK;
   }
 
   MaybeUpdatePrimaryTabParent(eTabParentRemoved);
@@ -2818,27 +2876,27 @@ nsFrameLoader::ResetPermissionManagerSta
 
   // Finding the new app Id:
   // . first we check if the owner is an app frame
   // . second, we check if the owner is a browser frame
   // in both cases we populate the appId variable.
   uint32_t appId = nsIScriptSecurityManager::NO_APP_ID;
   if (OwnerIsAppFrame()) {
     // You can't be both an app and a browser frame.
-    MOZ_ASSERT(!OwnerIsBrowserFrame());
+    MOZ_ASSERT(!OwnerIsMozBrowserFrame());
 
     nsCOMPtr<mozIApplication> ownApp = GetOwnApp();
     MOZ_ASSERT(ownApp);
     uint32_t ownAppId = nsIScriptSecurityManager::NO_APP_ID;
     if (ownApp && NS_SUCCEEDED(ownApp->GetLocalId(&ownAppId))) {
       appId = ownAppId;
     }
   }
 
-  if (OwnerIsBrowserFrame()) {
+  if (OwnerIsMozBrowserFrame()) {
     // You can't be both a browser and an app frame.
     MOZ_ASSERT(!OwnerIsAppFrame());
 
     nsCOMPtr<mozIApplication> containingApp = GetContainingApp();
     uint32_t containingAppId = nsIScriptSecurityManager::NO_APP_ID;
     if (containingApp && NS_SUCCEEDED(containingApp->GetLocalId(&containingAppId))) {
       appId = containingAppId;
     }
@@ -2966,17 +3024,17 @@ nsFrameLoader::GetLoadContext(nsILoadCon
   }
   loadContext.forget(aLoadContext);
   return NS_OK;
 }
 
 void
 nsFrameLoader::InitializeBrowserAPI()
 {
-  if (OwnerIsBrowserOrAppFrame()) {
+  if (OwnerIsMozBrowserOrAppFrame()) {
     if (!IsRemoteFrame()) {
       nsresult rv = EnsureMessageManager();
       if (NS_WARN_IF(NS_FAILED(rv))) {
         return;
       }
       if (mMessageManager) {
         mMessageManager->LoadFrameScript(
           NS_LITERAL_STRING("chrome://global/content/BrowserElementChild.js"),
@@ -3061,17 +3119,17 @@ nsFrameLoader::MaybeUpdatePrimaryTabPare
 nsresult
 nsFrameLoader::GetNewTabContext(MutableTabContext* aTabContext,
                                 nsIURI* aURI,
                                 const nsACString& aPackageId)
 {
   nsCOMPtr<mozIApplication> ownApp = GetOwnApp();
   nsCOMPtr<mozIApplication> containingApp = GetContainingApp();
   DocShellOriginAttributes attrs;
-  attrs.mInBrowser = OwnerIsBrowserFrame();
+  attrs.mInIsolatedMozBrowser = OwnerIsIsolatedMozBrowserFrame();
 
   nsCString signedPkgOrigin;
   if (!aPackageId.IsEmpty()) {
     // Only when aPackageId is not empty would signed package origin
     // be meaningful.
     nsPrincipal::GetOriginForURI(aURI, signedPkgOrigin);
   }
 
@@ -3102,13 +3160,17 @@ nsFrameLoader::GetNewTabContext(MutableT
   if (!userContextIdStr.IsEmpty()) {
     nsresult err;
     uint32_t userContextId = userContextIdStr.ToInteger(&err);
     NS_ENSURE_SUCCESS(err, err);
     attrs.mUserContextId = userContextId;
   }
 
   bool tabContextUpdated =
-    aTabContext->SetTabContext(ownApp, containingApp, attrs, signedPkgOrigin);
+    aTabContext->SetTabContext(OwnerIsMozBrowserFrame(),
+                               ownApp,
+                               containingApp,
+                               attrs,
+                               signedPkgOrigin);
   NS_ENSURE_STATE(tabContextUpdated);
 
   return NS_OK;
 }

--- a/dom/base/nsFrameLoader.h
+++ b/dom/base/nsFrameLoader.h
@@ -138,17 +138,17 @@ public:
    * Return the primary frame for our owning content, or null if it
    * can't be found.
    */
   nsIFrame* GetPrimaryFrameOfOwningContent() const
   {
     return mOwnerContent ? mOwnerContent->GetPrimaryFrame() : nullptr;
   }
 
-  /** 
+  /**
    * Return the document that owns this, or null if we don't have
    * an owner.
    */
   nsIDocument* GetOwnerDoc() const
   { return mOwnerContent ? mOwnerContent->OwnerDoc() : nullptr; }
 
   PBrowserParent* GetRemoteBrowser() const;
 
@@ -189,17 +189,17 @@ public:
 
   /**
    * Stashes a detached view on the frame loader. We do this when we're
    * destroying the nsSubDocumentFrame. If the nsSubdocumentFrame is
    * being reframed we'll restore the detached view when it's recreated,
    * otherwise we'll discard the old presentation and set the detached
    * subdoc view to null. aContainerDoc is the document containing the
    * the subdoc frame. This enables us to detect when the containing
-   * document has changed during reframe, so we can discard the presentation 
+   * document has changed during reframe, so we can discard the presentation
    * in that case.
    */
   void SetDetachedSubdocView(nsView* aDetachedView,
                              nsIDocument* aContainerDoc);
 
   /**
    * Retrieves the detached view and the document containing the view,
    * as set by SetDetachedSubdocView().
@@ -237,35 +237,46 @@ private:
    * Return true if the frame is a remote frame. Return false otherwise
    */
   bool IsRemoteFrame();
 
   /**
    * Is this a frameloader for a bona fide <iframe mozbrowser> or
    * <iframe mozapp>?  (I.e., does the frame return true for
    * nsIMozBrowserFrame::GetReallyIsBrowserOrApp()?)
+   * <xul:browser> is not a mozbrowser or app, so this is false for that case.
    */
-  bool OwnerIsBrowserOrAppFrame();
+  bool OwnerIsMozBrowserOrAppFrame();
 
   /**
    * Is this a frameloader for a bona fide <iframe mozwidget>?  (I.e., does the
    * frame return true for nsIMozBrowserFrame::GetReallyIsWidget()?)
    */
   bool OwnerIsWidget();
 
   /**
    * Is this a frameloader for a bona fide <iframe mozapp>?  (I.e., does the
    * frame return true for nsIMozBrowserFrame::GetReallyIsApp()?)
    */
   bool OwnerIsAppFrame();
 
   /**
    * Is this a frame loader for a bona fide <iframe mozbrowser>?
+   * <xul:browser> is not a mozbrowser, so this is false for that case.
    */
-  bool OwnerIsBrowserFrame();
+  bool OwnerIsMozBrowserFrame();
+
+  /**
+   * Is this a frame loader for an isolated <iframe mozbrowser>?
+   *
+   * By default, mozbrowser frames are isolated.  Isolation can be disabled by
+   * setting the frame's noisolation attribute.  Disabling isolation is
+   * only allowed if the containing document is chrome.
+   */
+  bool OwnerIsIsolatedMozBrowserFrame();
 
   /**
    * Get our owning element's app manifest URL, or return the empty string if
    * our owning element doesn't have an app manifest URL.
    */
   void GetOwnerAppManifestURL(nsAString& aOut);
 
   /**

--- a/dom/base/nsGkAtomList.h
+++ b/dom/base/nsGkAtomList.h
@@ -652,16 +652,17 @@ GK_ATOM(noautohide, "noautohide")
 GK_ATOM(norolluponanchor, "norolluponanchor")
 GK_ATOM(nobr, "nobr")
 GK_ATOM(node, "node")
 GK_ATOM(nodefaultsrc, "nodefaultsrc")
 GK_ATOM(nodeSet, "node-set")
 GK_ATOM(noembed, "noembed")
 GK_ATOM(noframes, "noframes")
 GK_ATOM(nohref, "nohref")
+GK_ATOM(noisolation, "noisolation")
 GK_ATOM(nonce, "nonce")
 GK_ATOM(none, "none")
 GK_ATOM(noresize, "noresize")
 GK_ATOM(normal, "normal")
 GK_ATOM(normalizeSpace, "normalize-space")
 GK_ATOM(noscript, "noscript")
 GK_ATOM(noshade, "noshade")
 GK_ATOM(novalidate, "novalidate")

--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -452,18 +452,16 @@ nsGlobalWindow::DOMMinTimeoutValue() con
     }                                                                         \
     return GetCurrentInnerWindowInternal()->method args;                      \
   }                                                                           \
   PR_END_MACRO
 
 // CIDs
 static NS_DEFINE_CID(kXULControllersCID, NS_XULCONTROLLERS_CID);
 
-static const char sPopStatePrefStr[] = "browser.history.allowPopState";
-
 #define NETWORK_UPLOAD_EVENT_NAME     NS_LITERAL_STRING("moznetworkupload")
 #define NETWORK_DOWNLOAD_EVENT_NAME   NS_LITERAL_STRING("moznetworkdownload")
 
 /**
  * An indirect observer object that means we don't have to implement nsIObserver
  * on nsGlobalWindow, where any script could see it.
  */
 class nsGlobalWindowObserver final : public nsIObserver,
@@ -1153,16 +1151,17 @@ nsGlobalWindow::nsGlobalWindow(nsGlobalW
     mFullscreenMode(false),
     mIsClosed(false),
     mInClose(false),
     mHavePendingClose(false),
     mHadOriginalOpener(false),
     mIsPopupSpam(false),
     mBlockScriptedClosingFlag(false),
     mWasOffline(false),
+    mHasHadSlowScript(false),
     mNotifyIdleObserversIdleOnThaw(false),
     mNotifyIdleObserversActiveOnThaw(false),
     mCreatingInnerWindow(false),
     mIsChrome(false),
     mCleanMessageManager(false),
     mNeedsFocus(true),
     mHasFocus(false),
 #if defined(XP_MACOSX)
@@ -3796,17 +3795,17 @@ nsGlobalWindow::GetParentOuter()
 {
   MOZ_RELEASE_ASSERT(IsOuterWindow());
 
   if (!mDocShell) {
     return nullptr;
   }
 
   nsCOMPtr<nsPIDOMWindowOuter> parent;
-  if (mDocShell->GetIsBrowserOrApp()) {
+  if (mDocShell->GetIsMozBrowserOrApp()) {
     parent = AsOuter();
   } else {
     parent = GetParent();
   }
 
   return parent.forget();
 }
 
@@ -3962,17 +3961,17 @@ nsGlobalWindow::GetContentInternal(Error
   nsCOMPtr<nsPIDOMWindowOuter> domWindow =
     GetChildWindow(NS_LITERAL_STRING("content"));
   if (domWindow) {
     return domWindow.forget();
   }
 
   // If we're contained in <iframe mozbrowser> or <iframe mozapp>, then
   // GetContent is the same as window.top.
-  if (mDocShell && mDocShell->GetIsInBrowserOrApp()) {
+  if (mDocShell && mDocShell->GetIsInMozBrowserOrApp()) {
     return GetTopOuter();
   }
 
   nsCOMPtr<nsIDocShellTreeItem> primaryContent;
   if (aUnprivilegedCaller) {
     // If we're called by non-chrome code, make sure we don't return
     // the primary content window if the calling tab is hidden. In
     // such a case we return the same-type root in the hidden tab,
@@ -7170,17 +7169,17 @@ void
 nsGlobalWindow::ResizeToOuter(int32_t aWidth, int32_t aHeight, ErrorResult& aError, bool aCallerIsChrome)
 {
   MOZ_RELEASE_ASSERT(IsOuterWindow());
 
   /*
    * If caller is a browser-element then dispatch a resize event to
    * the embedder.
    */
-  if (mDocShell && mDocShell->GetIsBrowserOrApp()) {
+  if (mDocShell && mDocShell->GetIsMozBrowserOrApp()) {
     CSSIntSize size(aWidth, aHeight);
     if (!DispatchResizeEvent(size)) {
       // The embedder chose to prevent the default action for this
       // event, so let's not resize this window after all...
       return;
     }
   }
 
@@ -7220,17 +7219,17 @@ nsGlobalWindow::ResizeByOuter(int32_t aW
                               ErrorResult& aError, bool aCallerIsChrome)
 {
   MOZ_RELEASE_ASSERT(IsOuterWindow());
 
   /*
    * If caller is a browser-element then dispatch a resize event to
    * parent.
    */
-  if (mDocShell && mDocShell->GetIsBrowserOrApp()) {
+  if (mDocShell && mDocShell->GetIsMozBrowserOrApp()) {
     CSSIntSize size;
     if (NS_FAILED(GetInnerSize(size))) {
       return;
     }
 
     size.width += aWidthDif;
     size.height += aHeightDif;
 
@@ -8169,17 +8168,17 @@ nsGlobalWindow::CanClose()
 }
 
 void
 nsGlobalWindow::CloseOuter(bool aTrustedCaller)
 {
   MOZ_RELEASE_ASSERT(IsOuterWindow());
 
   if (!mDocShell || IsInModalState() ||
-      (IsFrame() && !mDocShell->GetIsBrowserOrApp())) {
+      (IsFrame() && !mDocShell->GetIsMozBrowserOrApp())) {
     // window.close() is called on a frame in a frameset, on a window
     // that's already closed, or on a window for which there's
     // currently a modal dialog open. Ignore such calls.
     return;
   }
 
   if (mHavePendingClose) {
     // We're going to be closed anyway; do nothing since we don't want
@@ -8696,17 +8695,17 @@ nsGlobalWindow::CacheXBLPrototypeHandler
   mCachedXBLPrototypeHandlers->Put(aKey, aHandler);
 }
 
 Element*
 nsGlobalWindow::GetFrameElementOuter()
 {
   MOZ_RELEASE_ASSERT(IsOuterWindow());
 
-  if (!mDocShell || mDocShell->GetIsBrowserOrApp()) {
+  if (!mDocShell || mDocShell->GetIsMozBrowserOrApp()) {
     return nullptr;
   }
 
   // Per HTML5, the frameElement getter returns null in cross-origin situations.
   Element* element = GetRealFrameElementOuter();
   if (!element) {
     return nullptr;
   }
@@ -9911,21 +9910,16 @@ nsGlobalWindow::FireHashchange(const nsA
 
 nsresult
 nsGlobalWindow::DispatchSyncPopState()
 {
   MOZ_RELEASE_ASSERT(IsInnerWindow());
   NS_ASSERTION(nsContentUtils::IsSafeToRunScript(),
                "Must be safe to run script here.");
 
-  // Check that PopState hasn't been pref'ed off.
-  if (!Preferences::GetBool(sPopStatePrefStr, false)) {
-    return NS_OK;
-  }
-
   nsresult rv = NS_OK;
 
   // Bail if the window is frozen.
   if (IsFrozen()) {
     return NS_OK;
   }
 
   // Get the document's pending state object -- it contains the data we're
@@ -10657,16 +10651,23 @@ nsGlobalWindow::ShowSlowScriptDialog()
     return KillSlowScript;
   }
 
   // Check if we should offer the option to debug
   JS::UniqueChars filename;
   unsigned lineno;
   bool hasFrame = JS::DescribeScriptedCaller(cx, &filename, &lineno);
 
+  // Record the slow script event if we haven't done so already for this inner window
+  // (which represents a particular page to the user).
+  if (!mHasHadSlowScript) {
+    Telemetry::Accumulate(Telemetry::SLOW_SCRIPT_PAGE_COUNT, 1);
+  }
+  mHasHadSlowScript = true;
+
   if (XRE_IsContentProcess() &&
       ProcessHangMonitor::Get()) {
     ProcessHangMonitor::SlowScriptAction action;
     RefPtr<ProcessHangMonitor> monitor = ProcessHangMonitor::Get();
     nsCOMPtr<nsITabChild> child = do_GetInterface(GetDocShell());
     action = monitor->NotifySlowScript(child,
                                        filename.get(),
                                        lineno);

--- a/dom/base/nsGlobalWindow.h
+++ b/dom/base/nsGlobalWindow.h
@@ -1686,16 +1686,21 @@ protected:
   bool                          mIsPopupSpam : 1;
 
   // Indicates whether scripts are allowed to close this window.
   bool                          mBlockScriptedClosingFlag : 1;
 
   // Window offline status. Checked to see if we need to fire offline event
   bool                          mWasOffline : 1;
 
+  // Represents whether the inner window's page has had a slow script notice.
+  // Only used by inner windows; will always be false for outer windows.
+  // This is used to implement Telemetry measures such as SLOW_SCRIPT_PAGE_COUNT.
+  bool                          mHasHadSlowScript : 1;
+
   // Track what sorts of events we need to fire when thawed
   bool                          mNotifyIdleObserversIdleOnThaw : 1;
   bool                          mNotifyIdleObserversActiveOnThaw : 1;
 
   // Indicates whether we're in the middle of creating an initializing
   // a new inner window object.
   bool                          mCreatingInnerWindow : 1;
 

--- a/dom/base/nsHistory.cpp
+++ b/dom/base/nsHistory.cpp
@@ -20,21 +20,16 @@
 #include "nsContentUtils.h"
 #include "nsISHistory.h"
 #include "nsISHistoryInternal.h"
 #include "mozilla/Preferences.h"
 
 using namespace mozilla;
 using namespace mozilla::dom;
 
-static const char* sAllowPushStatePrefStr =
-  "browser.history.allowPushState";
-static const char* sAllowReplaceStatePrefStr =
-  "browser.history.allowReplaceState";
-
 //
 //  History class implementation
 //
 NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE_0(nsHistory)
 NS_IMPL_CYCLE_COLLECTING_ADDREF(nsHistory)
 NS_IMPL_CYCLE_COLLECTING_RELEASE(nsHistory)
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsHistory)
   NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
@@ -299,22 +294,16 @@ nsHistory::PushOrReplaceState(JSContext*
   }
 
   if (!win->HasActiveDocument()) {
     aRv.Throw(NS_ERROR_DOM_SECURITY_ERR);
 
     return;
   }
 
-  // Check that PushState hasn't been pref'ed off.
-  if (!Preferences::GetBool(aReplace ? sAllowReplaceStatePrefStr :
-                            sAllowPushStatePrefStr, false)) {
-    return;
-  }
-
   // AddState might run scripts, so we need to hold a strong reference to the
   // docShell here to keep it from going away.
   nsCOMPtr<nsIDocShell> docShell = win->GetDocShell();
 
   if (!docShell) {
     aRv.Throw(NS_ERROR_FAILURE);
 
     return;

--- a/dom/base/nsIFrameLoader.idl
+++ b/dom/base/nsIFrameLoader.idl
@@ -145,17 +145,17 @@ interface nsIFrameLoader : nsISupports
    * the child content process when these events are targeted to
    * the remote browser element.
    *
    * Used primarly for input events (mouse, keyboard)
    */
   const unsigned long EVENT_MODE_NORMAL_DISPATCH = 0x00000000;
 
   /**
-   * With this event mode, it's the application's responsability to 
+   * With this event mode, it's the application's responsability to
    * convert and forward events to the content process
    */
   const unsigned long EVENT_MODE_DONT_FORWARD_TO_CHILD = 0x00000001;
 
   attribute unsigned long eventMode;
 
   /**
    * If false, then the subdocument is not clipped to its CSS viewport, and the
@@ -191,24 +191,25 @@ interface nsIFrameLoader : nsISupports
    *
    * The notion of "visibility" here is separate from the notion of a
    * window/docshell's visibility.  This field is mostly here so that we can
    * have a notion of visibility in the parent process when frames are OOP.
    */
   [infallible] attribute boolean visible;
 
   /**
-   * Find out whether the owner content really is a browser or app frame
-   * Especially, a widget frame is regarded as an app frame.
+   * Find out whether the owner content really is a mozbrowser or app frame
+   * Especially, a widget frame is regarded as an app frame.  <xul:browser> is
+   * not considered to be a mozbrowser frame.
    */
-  readonly attribute boolean ownerIsBrowserOrAppFrame;
+  readonly attribute boolean ownerIsMozBrowserOrAppFrame;
 
   /**
    * Find out whether the owner content really is a widget. If this attribute
-   * returns true, |ownerIsBrowserOrAppFrame| must return true.
+   * returns true, |ownerIsMozBrowserOrAppFrame| must return true.
    */
   readonly attribute boolean ownerIsWidget;
 
 };
 
 %{C++
 class nsFrameLoader;
 %}

--- a/dom/base/nsJSEnvironment.cpp
+++ b/dom/base/nsJSEnvironment.cpp
@@ -1432,16 +1432,21 @@ TimeUntilNow(TimeStamp start)
   if (start.IsNull()) {
     return 0;
   }
   return TimeBetween(start, TimeStamp::Now());
 }
 
 struct CycleCollectorStats
 {
+  MOZ_CONSTEXPR CycleCollectorStats() :
+    mMaxGCDuration(0), mRanSyncForgetSkippable(false), mSuspected(0),
+    mMaxSkippableDuration(0), mMaxSliceTime(0), mMaxSliceTimeSinceClear(0),
+    mTotalSliceTime(0), mAnyLockedOut(false), mExtraForgetSkippableCalls(0) {}
+
   void Init()
   {
     Clear();
     mMaxSliceTimeSinceClear = 0;
   }
 
   void Clear()
   {