Bug 1533955 - Fire oop-browser-crashed event again if a subframe crashes. r=nika

This also adds an isTopFrame attribute to the FrameCrashedEvent binding, which
returns true if the frame that crashed was the top-most one.

Differential Revision: https://phabricator.services.mozilla.com/D29236

--HG--
extra : moz-landing-system : lando

dom/ipc/BrowserParent.cpp

@@ -485,11 +485,17 @@ void BrowserParent::ActorDestroy(ActorDestroyReason why) {
   // out-of-process iframe.
   RefPtr<nsFrameLoader> frameLoader = GetFrameLoader(true);
   nsCOMPtr<nsIObserverService> os = services::GetObserverService();
-  if (frameLoader && !mBrowserBridgeParent) {
+  if (frameLoader) {
     nsCOMPtr<Element> frameElement(mFrameElement);
     ReceiveMessage(CHILD_PROCESS_SHUTDOWN_MESSAGE, false, nullptr, nullptr,
                    nullptr);
-    frameLoader->DestroyComplete();
+
+    if (!mBrowsingContext->GetParent()) {
+      // If this is a top-level BrowsingContext, tell the frameloader it's time
+      // to go away. Otherwise, this is a subframe crash, and we can keep the
+      // frameloader around.
+      frameLoader->DestroyComplete();
+    }
 
     if (why == AbnormalShutdown && os) {
       os->NotifyObservers(ToSupports(frameLoader), "oop-frameloader-crashed",
@@ -513,6 +519,7 @@ void BrowserParent::ActorDestroy(ActorDestroyReason why) {
           init.mBubbles = true;
           init.mCancelable = true;
           init.mBrowsingContextId = mBrowsingContext->Id();
+          init.mIsTopFrame = !mBrowsingContext->GetParent();
 
           RefPtr<dom::FrameCrashedEvent> event =
               dom::FrameCrashedEvent::Constructor(frameElement->OwnerDoc(),

dom/webidl/FrameCrashedEvent.webidl

@@ -11,9 +11,15 @@ interface FrameCrashedEvent : Event
    * The browsingContextId of the frame that crashed.
    */
   readonly attribute unsigned long long browsingContextId;
+
+  /**
+   * True if the top-most frame crashed.
+   */
+  readonly attribute boolean isTopFrame;
 };
 
 dictionary FrameCrashedEventInit : EventInit
 {
   unsigned long long browsingContextId = 0;
+  boolean isTopFrame = false;
 };