Bug 1359017 - onmessageerror for BroadcastChannel in case StructuredClone algorithm fails when deserializing, r=masayuki, r=smaug

dom/broadcastchannel/BroadcastChannel.h

@@ -68,6 +68,7 @@ public:
   void Close();
 
   IMPL_EVENT_HANDLER(message)
+  IMPL_EVENT_HANDLER(messageerror)
 
   void Shutdown();
 

dom/broadcastchannel/BroadcastChannelChild.cpp

@@ -80,10 +80,10 @@ BroadcastChannelChild::RecvNotify(const ClonedMessageData& aData)
   JSContext* cx = jsapi.cx();
   JS::Rooted<JS::Value> value(cx, JS::NullValue());
   if (cloneData.DataLength()) {
-    ErrorResult rv;
+    IgnoredErrorResult rv;
     cloneData.Read(cx, &value, rv);
     if (NS_WARN_IF(rv.Failed())) {
-      rv.SuppressException();
+      DispatchError();
       return IPC_OK();
     }
   }
@@ -111,5 +111,21 @@ BroadcastChannelChild::ActorDestroy(ActorDestroyReason aWhy)
   mActorDestroyed = true;
 }
 
+void
+BroadcastChannelChild::DispatchError()
+{
+  MessageEventInit init;
+  init.mBubbles = false;
+  init.mCancelable = false;
+  init.mOrigin = mOrigin;
+
+  RefPtr<Event> event =
+    MessageEvent::Constructor(mBC, NS_LITERAL_STRING("messageerror"), init);
+  event->SetTrusted(true);
+
+  bool dummy;
+  mBC->DispatchEvent(event, &dummy);
+}
+
 } // namespace dom
 } // namespace mozilla

dom/broadcastchannel/BroadcastChannelChild.h

@@ -44,6 +44,8 @@ private:
 
   virtual void ActorDestroy(ActorDestroyReason aWhy) override;
 
+  void DispatchError();
+
   // This raw pointer is actually the parent object.
   // It's set to null when the parent object is deleted.
   BroadcastChannel* mBC;

dom/webidl/BroadcastChannel.webidl

@@ -4,7 +4,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  *
  * For more information on this interface, please see
- * http://www.whatwg.org/specs/web-apps/current-work/multipage/web-messaging.html#broadcasting-to-other-browsing-contexts
+ * https://html.spec.whatwg.org/#broadcastchannel
  */
 
 [Constructor(DOMString channel),
@@ -17,5 +17,6 @@ interface BroadcastChannel : EventTarget {
 
   void close();
 
-           attribute EventHandler onmessage;
+  attribute EventHandler onmessage;
+  attribute EventHandler onmessageerror;
 };