--- a/dom/base/nsFrameLoader.cpp
+++ b/dom/base/nsFrameLoader.cpp
@@ -3108,13 +3108,17 @@ 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/ipc/ContentChild.cpp
+++ b/dom/ipc/ContentChild.cpp
@@ -798,17 +798,17 @@ ContentChild::ProvideWindowCommon(TabChi
 
   nsAutoPtr<IPCTabContext> ipcContext;
   TabId openerTabId = TabId(0);
 
   if (aTabOpener) {
     PopupIPCTabContext context;
     openerTabId = aTabOpener->GetTabId();
     context.opener() = openerTabId;
-    context.isBrowserElement() = aTabOpener->IsBrowserElement();
+    context.isMozBrowserElement() = aTabOpener->IsMozBrowserElement();
     ipcContext = new IPCTabContext(context);
   } else {
     // It's possible to not have a TabChild opener in the case
     // of ServiceWorker::OpenWindow.
     UnsafeIPCTabContext unsafeTabContext;
     ipcContext = new IPCTabContext(unsafeTabContext);
   }
 

--- a/dom/ipc/ContentParent.cpp
+++ b/dom/ipc/ContentParent.cpp
@@ -1253,29 +1253,29 @@ ContentParent::CreateBrowserOrApp(const 
   TabId tabId;
 
   nsIDocShell* docShell = GetOpenerDocShellHelper(aFrameElement);
   TabId openerTabId;
   if (docShell) {
     openerTabId = TabParent::GetTabIdFrom(docShell);
   }
 
-  if (aContext.IsBrowserElement() || !aContext.HasOwnApp()) {
+  if (aContext.IsMozBrowserElement() || !aContext.HasOwnApp()) {
     RefPtr<TabParent> tp;
     RefPtr<nsIContentParent> constructorSender;
     if (isInContentProcess) {
-      MOZ_ASSERT(aContext.IsBrowserElement());
+      MOZ_ASSERT(aContext.IsMozBrowserElement());
       constructorSender = CreateContentBridgeParent(aContext, initialPriority,
                                                     openerTabId, &tabId);
     } else {
       if (aOpenerContentParent) {
         constructorSender = aOpenerContentParent;
       } else {
         constructorSender =
-          GetNewOrUsedBrowserProcess(aContext.IsBrowserElement(),
+          GetNewOrUsedBrowserProcess(aContext.IsMozBrowserElement(),
                                      initialPriority);
         if (!constructorSender) {
           return nullptr;
         }
       }
       tabId = AllocateTabId(openerTabId,
                             aContext.AsIPCTabContext(),
                            constructorSender->ChildID());
@@ -5440,17 +5440,17 @@ ContentParent::RecvCreateWindow(PBrowser
       return false;
   }
 
   TabParent* thisTabParent = nullptr;
   if (aThisTab) {
     thisTabParent = TabParent::GetFrom(aThisTab);
   }
 
-  if (NS_WARN_IF(thisTabParent && thisTabParent->IsBrowserOrApp())) {
+  if (NS_WARN_IF(thisTabParent && thisTabParent->IsMozBrowserOrApp())) {
     return false;
   }
 
   nsCOMPtr<nsPIWindowWatcher> pwwatch =
     do_GetService(NS_WINDOWWATCHER_CONTRACTID, aResult);
 
   if (NS_WARN_IF(NS_FAILED(*aResult))) {
     return true;

--- a/dom/ipc/PTabContext.ipdlh
+++ b/dom/ipc/PTabContext.ipdlh
@@ -8,45 +8,50 @@ include protocol PBrowser;
 include PBrowserOrId;
 
 namespace mozilla {
 namespace dom {
 
 // An IPCTabContext which corresponds to a PBrowser opened by a child when it
 // receives window.open().
 //
-// If isBrowserElement is false, this PopupIPCTabContext corresponds to an app
-// frame, and the frame's app-id and app-frame-owner-app-id will be equal to the
-// opener's values.
+// If isMozBrowserElement is false, this PopupIPCTabContext is either a
+// <xul:browser> or an app frame.  The frame's app-id and app-frame-owner-app-id
+// will be equal to the opener's values.  For a <xul:browser>, those app IDs
+// will be NO_APP_ID.
 //
-// If isBrowserElement is true, the frame's browserFrameOwnerAppId will be equal
-// to the opener's app-id.
+// If isMozBrowserElement is true, the frame's browserFrameOwnerAppId will be
+// equal to the opener's app-id.
 //
-// It's an error to set isBrowserElement == false if opener is a browser
+// It's an error to set isMozBrowserElement == false if opener is a mozbrowser
 // element.  Such a PopupIPCTabContext should be rejected by code which receives
 // it.
 struct PopupIPCTabContext
 {
   PBrowserOrId opener;
-  bool isBrowserElement;
+  bool isMozBrowserElement;
 };
 
 // An IPCTabContext which corresponds to an app, browser, or normal frame.
 struct FrameIPCTabContext
 {
   // The stringified originAttributes dictionary.
   nsCString originSuffix;
 
   // The ID of the app containing this app/browser frame, if applicable.
   uint32_t frameOwnerAppId;
 
   // The origin without originAttribute suffix for a signed package.
   // This value would be empty if the TabContext doesn't own a signed
   // package.
   nsCString signedPkgOriginNoSuffix;
+
+  // Whether this is a mozbrowser frame.  <iframe mozbrowser mozapp> and
+  // <xul:browser> are not considered to be mozbrowser frames.
+  bool isMozBrowserElement;
 };
 
 // XXXcatalinb: This is only used by ServiceWorkerClients::OpenWindow.
 // Because service workers don't have an associated TabChild
 // we can't satisfy the security constraints on b2g. As such, the parent
 // process will accept this tab context only on desktop.
 struct UnsafeIPCTabContext
 { };

--- a/dom/ipc/TabChild.cpp
+++ b/dom/ipc/TabChild.cpp
@@ -542,17 +542,17 @@ TabChild::PreloadSlowThings()
 /*static*/ already_AddRefed<TabChild>
 TabChild::Create(nsIContentChild* aManager,
                  const TabId& aTabId,
                  const TabContext &aContext,
                  uint32_t aChromeFlags)
 {
     if (sPreallocatedTab &&
         sPreallocatedTab->mChromeFlags == aChromeFlags &&
-        aContext.IsBrowserOrApp()) {
+        aContext.IsMozBrowserOrApp()) {
 
         RefPtr<TabChild> child = sPreallocatedTab.get();
         sPreallocatedTab = nullptr;
 
         MOZ_ASSERT(!child->mTriedBrowserInit);
 
         child->mManager = aManager;
         child->SetTabId(aTabId);
@@ -825,21 +825,19 @@ void
 TabChild::NotifyTabContextUpdated()
 {
     nsCOMPtr<nsIDocShell> docShell = do_GetInterface(WebNavigation());
     MOZ_ASSERT(docShell);
 
     if (docShell) {
         // nsDocShell will do the right thing if we pass NO_APP_ID or
         // UNKNOWN_APP_ID for aOwnOrContainingAppId.
-        if (IsBrowserElement()) {
+        if (IsMozBrowserElement()) {
           docShell->SetIsBrowserInsideApp(BrowserOwnerAppId());
-          // TODO: Wants to call TabContext::IsIsolatedMozBrowserElement() based
-          // on isolation in principal, which is added in a later patch.
-          docShell->SetIsInIsolatedMozBrowserElement(IsBrowserElement());
+          docShell->SetIsInIsolatedMozBrowserElement(IsIsolatedMozBrowserElement());
         } else {
           docShell->SetIsApp(OwnAppId());
         }
 
         OriginAttributes attrs = OriginAttributesRef();
         docShell->SetIsSignedPackage(attrs.mSignedPkg);
         docShell->SetUserContextId(attrs.mUserContextId);
     }
@@ -1466,17 +1464,17 @@ TabChild::ApplyShowInfo(const ShowInfo& 
     // Once we've got one ShowInfo from parent, no need to update the values
     // anymore.
     mDidSetRealShowInfo = true;
   }
 
   nsCOMPtr<nsIDocShell> docShell = do_GetInterface(WebNavigation());
   if (docShell) {
     nsCOMPtr<nsIDocShellTreeItem> item = do_GetInterface(docShell);
-    if (IsBrowserOrApp()) {
+    if (IsMozBrowserOrApp()) {
       // B2G allows window.name to be set by changing the name attribute on the
       // <iframe mozbrowser> element. window.open calls cause this attribute to
       // be set to the correct value. A normal <xul:browser> element has no such
       // attribute. The data we get here comes from reading the attribute, so we
       // shouldn't trust it for <xul:browser> elements.
       item->SetName(aInfo.name());
     }
     docShell->SetFullscreenAllowed(aInfo.fullscreenAllowed());
@@ -1503,17 +1501,17 @@ TabChild::ApplyShowInfo(const ShowInfo& 
 }
 
 #ifdef MOZ_WIDGET_GONK
 void
 TabChild::MaybeRequestPreinitCamera()
 {
     // Check if this tab is an app (not a browser frame) and will use the
     // `camera` permission,
-    if (IsBrowserElement()) {
+    if (IsIsolatedMozBrowserElement()) {
       return;
     }
 
     nsCOMPtr<nsIAppsService> appsService = do_GetService("@mozilla.org/AppsService;1");
     if (NS_WARN_IF(!appsService)) {
       return;
     }
 
@@ -2457,17 +2455,17 @@ TabChild::InitTabChildGlobal(FrameScript
     NS_ENSURE_TRUE(root, false);
     root->SetParentTarget(scope);
   }
 
   if (aScriptLoading != DONT_LOAD_SCRIPTS && !mTriedBrowserInit) {
     mTriedBrowserInit = true;
     // Initialize the child side of the browser element machinery,
     // if appropriate.
-    if (IsBrowserOrApp()) {
+    if (IsMozBrowserOrApp()) {
       RecvLoadRemoteScript(BROWSER_ELEMENT_CHILD_SCRIPT, true);
     }
   }
 
   return true;
 }
 
 bool

--- a/dom/ipc/TabContext.cpp
+++ b/dom/ipc/TabContext.cpp
@@ -17,31 +17,38 @@
 using namespace mozilla::dom::ipc;
 using namespace mozilla::layout;
 
 namespace mozilla {
 namespace dom {
 
 TabContext::TabContext()
   : mInitialized(false)
+  , mIsMozBrowserElement(false)
   , mContainingAppId(NO_APP_ID)
   , mOriginAttributes()
 {
 }
 
 bool
-TabContext::IsBrowserElement() const
+TabContext::IsMozBrowserElement() const
+{
+  return mIsMozBrowserElement;
+}
+
+bool
+TabContext::IsIsolatedMozBrowserElement() const
 {
   return mOriginAttributes.mInIsolatedMozBrowser;
 }
 
 bool
-TabContext::IsBrowserOrApp() const
+TabContext::IsMozBrowserOrApp() const
 {
-  return HasOwnApp() || IsBrowserElement();
+  return HasOwnApp() || IsMozBrowserElement();
 }
 
 uint32_t
 TabContext::OwnAppId() const
 {
   return mOriginAttributes.mAppId;
 }
 
@@ -57,27 +64,27 @@ TabContext::HasOwnApp() const
 {
   nsCOMPtr<mozIApplication> ownApp = GetOwnApp();
   return !!ownApp;
 }
 
 uint32_t
 TabContext::BrowserOwnerAppId() const
 {
-  if (IsBrowserElement()) {
+  if (IsMozBrowserElement()) {
     return mContainingAppId;
   }
   return NO_APP_ID;
 }
 
 already_AddRefed<mozIApplication>
 TabContext::GetBrowserOwnerApp() const
 {
   nsCOMPtr<mozIApplication> ownerApp;
-  if (IsBrowserElement()) {
+  if (IsMozBrowserElement()) {
     ownerApp = mContainingApp;
   }
   return ownerApp.forget();
 }
 
 bool
 TabContext::HasBrowserOwnerApp() const
 {
@@ -160,17 +167,18 @@ TabContext::OriginAttributesRef() const
 
 const nsACString&
 TabContext::SignedPkgOriginNoSuffix() const
 {
   return mSignedPkgOriginNoSuffix;
 }
 
 bool
-TabContext::SetTabContext(mozIApplication* aOwnApp,
+TabContext::SetTabContext(bool aIsMozBrowserElement,
+                          mozIApplication* aOwnApp,
                           mozIApplication* aAppFrameOwnerApp,
                           const DocShellOriginAttributes& aOriginAttributes,
                           const nsACString& aSignedPkgOriginNoSuffix)
 {
   NS_ENSURE_FALSE(mInitialized, false);
 
   // Get ids for both apps and only write to our member variables after we've
   // verified that this worked.
@@ -189,32 +197,34 @@ TabContext::SetTabContext(mozIApplicatio
   }
 
   // Veryify that app id matches mAppId passed in originAttributes
   MOZ_RELEASE_ASSERT((aOwnApp && aOriginAttributes.mAppId == ownAppId) ||
                      (aAppFrameOwnerApp && aOriginAttributes.mAppId == containingAppId) ||
                      aOriginAttributes.mAppId == NO_APP_ID);
 
   mInitialized = true;
+  mIsMozBrowserElement = aIsMozBrowserElement;
   mOriginAttributes = aOriginAttributes;
   mContainingAppId = containingAppId;
   mOwnApp = aOwnApp;
   mContainingApp = aAppFrameOwnerApp;
   mSignedPkgOriginNoSuffix = aSignedPkgOriginNoSuffix;
   return true;
 }
 
 IPCTabContext
 TabContext::AsIPCTabContext() const
 {
   nsAutoCString originSuffix;
   mOriginAttributes.CreateSuffix(originSuffix);
   return IPCTabContext(FrameIPCTabContext(originSuffix,
                                           mContainingAppId,
-                                          mSignedPkgOriginNoSuffix));
+                                          mSignedPkgOriginNoSuffix,
+                                          mIsMozBrowserElement));
 }
 
 static already_AddRefed<mozIApplication>
 GetAppForId(uint32_t aAppId)
 {
   nsCOMPtr<nsIAppsService> appsService = do_GetService(APPS_SERVICE_CONTRACTID);
   NS_ENSURE_TRUE(appsService, nullptr);
 
@@ -222,29 +232,31 @@ GetAppForId(uint32_t aAppId)
   appsService->GetAppByLocalId(aAppId, getter_AddRefs(app));
 
   return app.forget();
 }
 
 MaybeInvalidTabContext::MaybeInvalidTabContext(const IPCTabContext& aParams)
   : mInvalidReason(nullptr)
 {
+  bool isMozBrowserElement = false;
   uint32_t containingAppId = NO_APP_ID;
   DocShellOriginAttributes originAttributes;
   nsAutoCString originSuffix;
   nsAutoCString signedPkgOriginNoSuffix;
 
   switch(aParams.type()) {
     case IPCTabContext::TPopupIPCTabContext: {
       const PopupIPCTabContext &ipcContext = aParams.get_PopupIPCTabContext();
 
       TabContext *context;
       if (ipcContext.opener().type() == PBrowserOrId::TPBrowserParent) {
         context = TabParent::GetFrom(ipcContext.opener().get_PBrowserParent());
-        if (context->IsBrowserElement() && !ipcContext.isBrowserElement()) {
+        if (context->IsMozBrowserElement() &&
+            !ipcContext.isMozBrowserElement()) {
           // If the TabParent corresponds to a browser element, then it can only
           // open other browser elements, for security reasons.  We should have
           // checked this before calling the TabContext constructor, so this is
           // a fatal error.
           mInvalidReason = "Child is-browser process tried to "
                            "open a non-browser tab.";
           return;
         }
@@ -264,28 +276,30 @@ MaybeInvalidTabContext::MaybeInvalidTabC
 
       // Browser elements can't nest other browser elements.  So if
       // our opener is browser element, we must be a new DOM window
       // opened by it.  In that case we inherit our containing app ID
       // (if any).
       //
       // Otherwise, we're a new app window and we inherit from our
       // opener app.
+      isMozBrowserElement = ipcContext.isMozBrowserElement();
       originAttributes = context->mOriginAttributes;
-      if (ipcContext.isBrowserElement()) {
+      if (isMozBrowserElement) {
         containingAppId = context->OwnOrContainingAppId();
       } else {
         containingAppId = context->mContainingAppId;
       }
       break;
     }
     case IPCTabContext::TFrameIPCTabContext: {
       const FrameIPCTabContext &ipcContext =
         aParams.get_FrameIPCTabContext();
 
+      isMozBrowserElement = ipcContext.isMozBrowserElement();
       containingAppId = ipcContext.frameOwnerAppId();
       signedPkgOriginNoSuffix = ipcContext.signedPkgOriginNoSuffix();
       originSuffix = ipcContext.originSuffix();
       originAttributes.PopulateFromSuffix(originSuffix);
       break;
     }
     case IPCTabContext::TUnsafeIPCTabContext: {
       // XXXcatalinb: This used *only* by ServiceWorkerClients::OpenWindow.
@@ -305,34 +319,35 @@ MaybeInvalidTabContext::MaybeInvalidTabC
       break;
     }
     default: {
       MOZ_CRASH();
     }
   }
 
   nsCOMPtr<mozIApplication> ownApp;
-  if (!originAttributes.mInIsolatedMozBrowser) {
-    // mAppId corresponds to OwnOrContainingAppId; if mInIsolatedMozBrowser is
+  if (!isMozBrowserElement) {
+    // mAppId corresponds to OwnOrContainingAppId; if isMozBrowserElement is
     // false then it's ownApp otherwise it's containingApp
     ownApp = GetAppForId(originAttributes.mAppId);
     if ((ownApp == nullptr) != (originAttributes.mAppId == NO_APP_ID)) {
       mInvalidReason = "Got an ownAppId that didn't correspond to an app.";
       return;
     }
   }
 
   nsCOMPtr<mozIApplication> containingApp = GetAppForId(containingAppId);
   if ((containingApp == nullptr) != (containingAppId == NO_APP_ID)) {
     mInvalidReason = "Got a containingAppId that didn't correspond to an app.";
     return;
   }
 
   bool rv;
-  rv = mTabContext.SetTabContext(ownApp,
+  rv = mTabContext.SetTabContext(isMozBrowserElement,
+                                 ownApp,
                                  containingApp,
                                  originAttributes,
                                  signedPkgOriginNoSuffix);
   if (!rv) {
     mInvalidReason = "Couldn't initialize TabContext.";
   }
 }
 

--- a/dom/ipc/TabContext.h
+++ b/dom/ipc/TabContext.h
@@ -37,47 +37,61 @@ public:
 
   /**
    * Generates IPCTabContext of type BrowserFrameIPCTabContext or
    * AppFrameIPCTabContext from this TabContext's information.
    */
   IPCTabContext AsIPCTabContext() const;
 
   /**
-   * Does this TabContext correspond to a mozbrowser?  (<iframe mozbrowser
-   * mozapp> is not a browser.)
+   * Does this TabContext correspond to a mozbrowser?
    *
-   * If IsBrowserElement() is true, HasOwnApp() and HasAppOwnerApp() are
+   * <iframe mozbrowser mozapp> and <xul:browser> are not considered to be
+   * mozbrowser elements.
+   *
+   * If IsMozBrowserElement() is true, HasOwnApp() and HasAppOwnerApp() are
    * guaranteed to be false.
    *
-   * If IsBrowserElement() is false, HasBrowserOwnerApp() is guaranteed to be
+   * If IsMozBrowserElement() is false, HasBrowserOwnerApp() is guaranteed to be
    * false.
    */
-  bool IsBrowserElement() const;
+  bool IsMozBrowserElement() const;
+
+  /**
+   * Does this TabContext correspond to an isolated 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 by
+   * chrome pages.
+   */
+  bool IsIsolatedMozBrowserElement() const;
 
   /**
    * Does this TabContext correspond to a mozbrowser or mozapp?  This is
-   * equivalent to IsBrowserElement() || HasOwnApp().
+   * equivalent to IsMozBrowserElement() || HasOwnApp().  Returns false for
+   * <xul:browser>, which is neither a mozbrowser nor a mozapp.
    */
-  bool IsBrowserOrApp() const;
+  bool IsMozBrowserOrApp() const;
 
   /**
    * OwnAppId() returns the id of the app which directly corresponds to this
    * context's frame.  GetOwnApp() returns the corresponding app object, and
    * HasOwnApp() returns true iff GetOwnApp() would return a non-null value.
    *
-   * If HasOwnApp() is true, IsBrowserElement() is guaranteed to be false.
+   * If HasOwnApp() is true, IsMozBrowserElement() is guaranteed to be
+   * false.
    */
   uint32_t OwnAppId() const;
   already_AddRefed<mozIApplication> GetOwnApp() const;
   bool HasOwnApp() const;
 
   /**
    * BrowserOwnerAppId() gets the ID of the app which contains this browser
-   * frame.  If this is not a browser frame (i.e., if !IsBrowserElement()), then
+   * frame.  If this is not a mozbrowser frame (if !IsMozBrowserElement()), then
    * BrowserOwnerAppId() is guaranteed to return NO_APP_ID.
    *
    * Even if we are a browser frame, BrowserOwnerAppId() may still return
    * NO_APP_ID, if this browser frame is not contained inside an app.
    */
   uint32_t BrowserOwnerAppId() const;
   already_AddRefed<mozIApplication> GetBrowserOwnerApp() const;
   bool HasBrowserOwnerApp() const;
@@ -135,37 +149,46 @@ protected:
 
   /**
    * Set the TabContext for this frame. This can either be:
    *  - an app frame (with the given own app) inside the given owner app. Either
    *    apps can be null.
    *  - a browser frame inside the given owner app (which may be null).
    *  - a non-browser, non-app frame. Both own app and owner app should be null.
    */
-  bool SetTabContext(mozIApplication* aOwnApp,
+  bool SetTabContext(bool aIsMozBrowserElement,
+                     mozIApplication* aOwnApp,
                      mozIApplication* aAppFrameOwnerApp,
                      const DocShellOriginAttributes& aOriginAttributes,
                      const nsACString& aSignedPkgOriginNoSuffix);
 
 private:
   /**
    * Has this TabContext been initialized?  If so, mutator methods will fail.
    */
   bool mInitialized;
 
   /**
+   * Whether this TabContext corresponds to a mozbrowser.
+   *
+   * <iframe mozbrowser mozapp> and <xul:browser> are not considered to be
+   * mozbrowser elements.
+   */
+  bool mIsMozBrowserElement;
+
+  /**
    * This TabContext's own app.  If this is non-null, then this
-   * TabContext corresponds to an app, and mIsBrowser must be false.
+   * TabContext corresponds to an app, and mIsMozBrowserElement must be false.
    */
   nsCOMPtr<mozIApplication> mOwnApp;
 
   /**
-   * This TabContext's containing app.  If mIsBrowser, this corresponds to the
-   * app which contains the browser frame; otherwise, this corresponds to the
-   * app which contains the app frame.
+   * This TabContext's containing app.  If mIsMozBrowserElement, this
+   * corresponds to the app which contains the browser frame; otherwise, this
+   * corresponds to the app which contains the app frame.
    */
   nsCOMPtr<mozIApplication> mContainingApp;
 
   /*
    * Cache of mContainingApp->GetLocalId().
    */
   uint32_t mContainingAppId;
 
@@ -192,22 +215,24 @@ class MutableTabContext : public TabCont
 {
 public:
   bool SetTabContext(const TabContext& aContext)
   {
     return TabContext::SetTabContext(aContext);
   }
 
   bool
-  SetTabContext(mozIApplication* aOwnApp,
+  SetTabContext(bool aIsMozBrowserElement,
+                mozIApplication* aOwnApp,
                 mozIApplication* aAppFrameOwnerApp,
                 const DocShellOriginAttributes& aOriginAttributes,
                 const nsACString& aSignedPkgOriginNoSuffix = EmptyCString())
   {
-    return TabContext::SetTabContext(aOwnApp,
+    return TabContext::SetTabContext(aIsMozBrowserElement,
+                                     aOwnApp,
                                      aAppFrameOwnerApp,
                                      aOriginAttributes,
                                      aSignedPkgOriginNoSuffix);
   }
 };
 
 /**
  * MaybeInvalidTabContext is a simple class that lets you transform an

--- a/dom/ipc/nsIContentParent.cpp
+++ b/dom/ipc/nsIContentParent.cpp
@@ -89,20 +89,20 @@ nsIContentParent::CanOpenBrowser(const I
     }
 
     auto opener = TabParent::GetFrom(popupContext.opener().get_PBrowserParent());
     if (!opener) {
       ASSERT_UNLESS_FUZZING("Got null opener from child; aborting AllocPBrowserParent.");
       return false;
     }
 
-    // Popup windows of isBrowser frames must be isBrowser if the parent
-    // isBrowser.  Allocating a !isBrowser frame with same app ID would allow
-    // the content to access data it's not supposed to.
-    if (!popupContext.isBrowserElement() && opener->IsBrowserElement()) {
+    // Popup windows of isMozBrowserElement frames must be isMozBrowserElement if
+    // the parent isMozBrowserElement.  Allocating a !isMozBrowserElement frame with
+    // same app ID would allow the content to access data it's not supposed to.
+    if (!popupContext.isMozBrowserElement() && opener->IsMozBrowserElement()) {
       ASSERT_UNLESS_FUZZING("Child trying to escalate privileges!  Aborting AllocPBrowserParent.");
       return false;
     }
   }
 
   MaybeInvalidTabContext tc(aContext);
   if (!tc.IsValid()) {
     NS_ERROR(nsPrintfCString("Child passed us an invalid TabContext.  (%s)  "

--- a/dom/network/TCPServerSocket.cpp
+++ b/dom/network/TCPServerSocket.cpp
@@ -143,17 +143,17 @@ TCPServerSocket::FireEvent(const nsAStri
 
 NS_IMETHODIMP
 TCPServerSocket::OnSocketAccepted(nsIServerSocket* aServer, nsISocketTransport* aTransport)
 {
   nsCOMPtr<nsIGlobalObject> global = GetOwnerGlobal();
   RefPtr<TCPSocket> socket = TCPSocket::CreateAcceptedSocket(global, aTransport, mUseArrayBuffers);
   if (mServerBridgeParent) {
     socket->SetAppIdAndBrowser(mServerBridgeParent->GetAppId(),
-                               mServerBridgeParent->GetInBrowser());
+                               mServerBridgeParent->GetInIsolatedMozBrowser());
   }
   FireEvent(NS_LITERAL_STRING("connect"), socket);
   return NS_OK;
 }
 
 NS_IMETHODIMP
 TCPServerSocket::OnStopListening(nsIServerSocket* aServer, nsresult aStatus)
 {

--- a/dom/network/TCPServerSocketParent.cpp
+++ b/dom/network/TCPServerSocketParent.cpp
@@ -70,22 +70,22 @@ TCPServerSocketParent::GetAppId()
     TabParent *tab = TabParent::GetFrom(browser);
     return tab->OwnAppId();
   } else {
     return nsIScriptSecurityManager::UNKNOWN_APP_ID;
   }
 }
 
 bool
-TCPServerSocketParent::GetInBrowser()
+TCPServerSocketParent::GetInIsolatedMozBrowser()
 {
   const PContentParent *content = Manager()->Manager();
   if (PBrowserParent* browser = SingleManagedOrNull(content->ManagedPBrowserParent())) {
     TabParent *tab = TabParent::GetFrom(browser);
-    return tab->IsBrowserElement();
+    return tab->IsIsolatedMozBrowserElement();
   } else {
     return false;
   }
 }
 
 nsresult
 TCPServerSocketParent::SendCallbackAccept(TCPSocketParent *socket)
 {
@@ -145,17 +145,17 @@ TCPServerSocketParent::RecvRequestDelete
   mozilla::Unused << Send__delete__(this);
   return true;
 }
 
 void
 TCPServerSocketParent::OnConnect(TCPServerSocketEvent* event)
 {
   RefPtr<TCPSocket> socket = event->Socket();
-  socket->SetAppIdAndBrowser(GetAppId(), GetInBrowser());
+  socket->SetAppIdAndBrowser(GetAppId(), GetInIsolatedMozBrowser());
 
   RefPtr<TCPSocketParent> socketParent = new TCPSocketParent();
   socketParent->SetSocket(socket);
 
   socket->SetSocketBridgeParent(socketParent);
 
   SendCallbackAccept(socketParent);
 }

--- a/dom/network/TCPServerSocketParent.h
+++ b/dom/network/TCPServerSocketParent.h
@@ -30,17 +30,17 @@ public:
                         uint16_t aBacklog, bool aUseArrayBuffers);
 
   void Init();
 
   virtual bool RecvClose() override;
   virtual bool RecvRequestDelete() override;
 
   uint32_t GetAppId();
-  bool GetInBrowser();
+  bool GetInIsolatedMozBrowser();
 
   void AddIPDLReference();
   void ReleaseIPDLReference();
 
   void OnConnect(TCPServerSocketEvent* event);
 
 private:
   ~TCPServerSocketParent();

--- a/dom/network/TCPSocket.cpp
+++ b/dom/network/TCPSocket.cpp
@@ -161,17 +161,17 @@ TCPSocket::TCPSocket(nsIGlobalObject* aG
   , mBufferedAmount(0)
   , mSuspendCount(0)
   , mTrackingNumber(0)
   , mWaitingForStartTLS(false)
 #ifdef MOZ_WIDGET_GONK
   , mTxBytes(0)
   , mRxBytes(0)
   , mAppId(nsIScriptSecurityManager::UNKNOWN_APP_ID)
-  , mInBrowser(false)
+  , mInIsolatedMozBrowser(false)
 #endif
 {
   if (aGlobal) {
     nsCOMPtr<nsPIDOMWindowInner> window = do_QueryInterface(aGlobal);
     if (window) {
       mInnerWindowID = window->WindowID();
     }
   }
@@ -1095,21 +1095,21 @@ TCPSocket::OnStopRequest(nsIRequest* aRe
 
 void
 TCPSocket::SetSocketBridgeParent(TCPSocketParent* aBridgeParent)
 {
   mSocketBridgeParent = aBridgeParent;
 }
 
 void
-TCPSocket::SetAppIdAndBrowser(uint32_t aAppId, bool aInBrowser)
+TCPSocket::SetAppIdAndBrowser(uint32_t aAppId, bool aInIsolatedMozBrowser)
 {
 #ifdef MOZ_WIDGET_GONK
   mAppId = aAppId;
-  mInBrowser = aInBrowser;
+  mInIsolatedMozBrowser = aInIsolatedMozBrowser;
 #endif
 }
 
 NS_IMETHODIMP
 TCPSocket::UpdateReadyState(uint32_t aReadyState)
 {
   MOZ_ASSERT(mSocketBridgeChild);
   mReadyState = static_cast<TCPReadyState>(aReadyState);
@@ -1150,18 +1150,18 @@ TCPSocket::SaveNetworkStats(bool aEnforc
   }
 
   nsCOMPtr<nsINetworkStatsServiceProxy> nssProxy =
     do_GetService("@mozilla.org/networkstatsServiceProxy;1");
   if (!nssProxy) {
     return;
   }
 
-  nssProxy->SaveAppStats(mAppId, mInBrowser, mActiveNetworkInfo, PR_Now(),
-                         mRxBytes, mTxBytes, false, nullptr);
+  nssProxy->SaveAppStats(mAppId, mInIsolatedMozBrowser, mActiveNetworkInfo,
+                         PR_Now(), mRxBytes, mTxBytes, false, nullptr);
 
   // Reset the counters once the statistics is saved to NetworkStatsServiceProxy.
   mTxBytes = mRxBytes = 0;
 }
 #endif
 
 NS_IMETHODIMP
 TCPSocket::Observe(nsISupports* aSubject, const char* aTopic, const char16_t* aData)

--- a/dom/network/TCPSocket.h
+++ b/dom/network/TCPSocket.h
@@ -237,18 +237,18 @@ private:
 
 #ifdef MOZ_WIDGET_GONK
   // Number of bytes sent.
   uint32_t mTxBytes;
   // Number of bytes received.
   uint32_t mRxBytes;
   // The app that owns this socket.
   uint32_t mAppId;
-  // Was this socket created inside of a mozbrowser frame?
-  bool mInBrowser;
+  // Was this socket created inside of an isolated browser frame?
+  bool mInIsolatedMozBrowser;
   // The name of the active network used by this socket.
   nsCOMPtr<nsINetworkInfo> mActiveNetworkInfo;
 #endif
 };
 
 } // namespace dom
 } // namespace mozilla
 

--- a/dom/network/TCPSocketParent.cpp
+++ b/dom/network/TCPSocketParent.cpp
@@ -72,22 +72,22 @@ TCPSocketParent::GetAppId()
     TabParent *tab = TabParent::GetFrom(browser);
     return tab->OwnAppId();
   } else {
     return nsIScriptSecurityManager::UNKNOWN_APP_ID;
   }
 };
 
 bool
-TCPSocketParent::GetInBrowser()
+TCPSocketParent::GetInIsolatedMozBrowser()
 {
   const PContentParent *content = Manager()->Manager();
   if (PBrowserParent* browser = SingleManagedOrNull(content->ManagedPBrowserParent())) {
     TabParent *tab = TabParent::GetFrom(browser);
-    return tab->IsBrowserElement();
+    return tab->IsIsolatedMozBrowserElement();
   } else {
     return false;
   }
 }
 
 nsresult
 TCPSocketParent::OfflineNotification(nsISupports *aSubject)
 {
@@ -150,26 +150,26 @@ TCPSocketParent::RecvOpen(const nsString
   if (net::UsingNeckoIPCSecurity() &&
       !AssertAppProcessPermission(Manager()->Manager(), "tcp-socket")) {
     FireInteralError(this, __LINE__);
     return true;
   }
 
   // Obtain App ID
   uint32_t appId = GetAppId();
-  bool     inBrowser = GetInBrowser();
+  bool     inIsolatedMozBrowser = GetInIsolatedMozBrowser();
 
   if (NS_IsAppOffline(appId)) {
     NS_ERROR("Can't open socket because app is offline");
     FireInteralError(this, __LINE__);
     return true;
   }
 
   mSocket = new TCPSocket(nullptr, aHost, aPort, aUseSSL, aUseArrayBuffers);
-  mSocket->SetAppIdAndBrowser(appId, inBrowser);
+  mSocket->SetAppIdAndBrowser(appId, inIsolatedMozBrowser);
   mSocket->SetSocketBridgeParent(this);
   NS_ENSURE_SUCCESS(mSocket->Init(), true);
   return true;
 }
 
 bool
 TCPSocketParent::RecvOpenBind(const nsCString& aRemoteHost,
                               const uint16_t& aRemotePort,
@@ -216,28 +216,28 @@ TCPSocketParent::RecvOpenBind(const nsCS
   rv = socketTransport->Bind(&addr);
   if (NS_FAILED(rv)) {
     FireInteralError(this, __LINE__);
     return true;
   }
 
   // Obtain App ID
   uint32_t appId = nsIScriptSecurityManager::NO_APP_ID;
-  bool     inBrowser = false;
+  bool     inIsolatedMozBrowser = false;
   const PContentParent *content = Manager()->Manager();
   if (PBrowserParent* browser = SingleManagedOrNull(content->ManagedPBrowserParent())) {
     // appId's are for B2G only currently, where managees.Count() == 1
     // This is not guaranteed currently in Desktop, so skip this there.
     TabParent *tab = TabParent::GetFrom(browser);
     appId = tab->OwnAppId();
-    inBrowser = tab->IsBrowserElement();
+    inIsolatedMozBrowser = tab->IsIsolatedMozBrowserElement();
   }
 
   mSocket = new TCPSocket(nullptr, NS_ConvertUTF8toUTF16(aRemoteHost), aRemotePort, aUseSSL, aUseArrayBuffers);
-  mSocket->SetAppIdAndBrowser(appId, inBrowser);
+  mSocket->SetAppIdAndBrowser(appId, inIsolatedMozBrowser);
   mSocket->SetSocketBridgeParent(this);
   rv = mSocket->InitWithUnconnectedTransport(socketTransport);
   NS_ENSURE_SUCCESS(rv, true);
   return true;
 }
 
 bool
 TCPSocketParent::RecvStartTLS()

--- a/dom/network/TCPSocketParent.h
+++ b/dom/network/TCPSocketParent.h
@@ -63,17 +63,17 @@ public:
   virtual bool RecvSuspend() override;
   virtual bool RecvResume() override;
   virtual bool RecvClose() override;
   virtual bool RecvData(const SendableData& aData,
                         const uint32_t& aTrackingNumber) override;
   virtual bool RecvRequestDelete() override;
   virtual nsresult OfflineNotification(nsISupports *) override;
   virtual uint32_t GetAppId() override;
-  bool GetInBrowser();
+  bool GetInIsolatedMozBrowser();
 
   void FireErrorEvent(const nsAString& aName, const nsAString& aType, TCPReadyState aReadyState);
   void FireEvent(const nsAString& aType, TCPReadyState aReadyState);
   void FireArrayBufferDataEvent(nsTArray<uint8_t>& aBuffer, TCPReadyState aReadyState);
   void FireStringDataEvent(const nsACString& aData, TCPReadyState aReadyState);
 
   void SetSocket(TCPSocket *socket);
   nsresult GetHost(nsAString& aHost);

--- a/dom/workers/ServiceWorkerManagerService.cpp
+++ b/dom/workers/ServiceWorkerManagerService.cpp
@@ -63,17 +63,17 @@ public:
         // mContentParent needs to be released in the main thread.
         data.mContentParent = nullptr;
         // We only send the notification about the soft update to the
         // tabs/apps with the same appId and inIsolatedMozBrowser values.
         // Sending a notification to the wrong process will make the process
         // to be killed.
         for (uint32_t j = 0; j < contextArray.Length(); ++j) {
           if ((contextArray[j].OwnOrContainingAppId() == mOriginAttributes.mAppId) &&
-              (contextArray[j].IsBrowserElement() == mOriginAttributes.mInIsolatedMozBrowser)) {
+              (contextArray[j].IsIsolatedMozBrowserElement() == mOriginAttributes.mInIsolatedMozBrowser)) {
             continue;
           }
           // Array entries with no mParent won't receive any notification.
           data.mParent = nullptr;
         }
       }
       nsresult rv = mBackgroundThread->Dispatch(this, NS_DISPATCH_NORMAL);
       MOZ_ALWAYS_TRUE(NS_SUCCEEDED(rv));

--- a/netwerk/ipc/NeckoParent.cpp
+++ b/netwerk/ipc/NeckoParent.cpp
@@ -123,27 +123,27 @@ NeckoParent::GetValidatedAppInfo(const S
 
   nsTArray<TabContext> contextArray =
     static_cast<ContentParent*>(aContent)->GetManagedTabContext();
   for (uint32_t i = 0; i < contextArray.Length(); i++) {
     TabContext tabContext = contextArray[i];
     uint32_t appId = tabContext.OwnOrContainingAppId();
     bool inBrowserElement = aSerialized.IsNotNull() ?
                               aSerialized.mOriginAttributes.mInIsolatedMozBrowser :
-                              tabContext.IsBrowserElement();
+                              tabContext.IsIsolatedMozBrowserElement();
 
     if (appId == NECKO_UNKNOWN_APP_ID) {
       continue;
     }
     // We may get appID=NO_APP if child frame is neither a browser nor an app
     if (appId == NECKO_NO_APP_ID) {
       if (tabContext.HasOwnApp()) {
         continue;
       }
-      if (UsingNeckoIPCSecurity() && tabContext.IsBrowserElement()) {
+      if (UsingNeckoIPCSecurity() && tabContext.IsIsolatedMozBrowserElement()) {
         // <iframe mozbrowser> which doesn't have an <iframe mozapp> above it.
         // This is not supported now, and we'll need to do a code audit to make
         // sure we can handle it (i.e don't short-circuit using separate
         // namespace if just appID==0)
         continue;
       }
     }