Bug 916685, no need to store empty event handlers, r=bz

--HG--
extra : rebase_source : 4a1b7e5e177744438f6bb59d58b0e2f6e2fe3b5c

content/events/src/nsEventListenerManager.cpp

@@ -900,7 +900,9 @@ nsEventListenerManager::CompileEventHandlerInternal(nsListenerStruct *aListenerS
     JS::Rooted<JSObject*> boundHandler(cx);
     JS::Rooted<JSObject*> scope(cx, listener->GetEventScope());
     context->BindCompiledEventHandler(mTarget, scope, handler, &boundHandler);
-    if (listener->EventName() == nsGkAtoms::onerror && win) {
+    if (!boundHandler) {
+      listener->ForgetHandler();
+    } else if (listener->EventName() == nsGkAtoms::onerror && win) {
       nsRefPtr<OnErrorEventHandlerNonNull> handlerCallback =
         new OnErrorEventHandlerNonNull(boundHandler);
       listener->SetHandler(handlerCallback);

dom/base/nsIJSEventListener.h

@@ -214,6 +214,11 @@ public:
     return mHandler;
   }
 
+  void ForgetHandler()
+  {
+    mHandler.ForgetHandler();
+  }
+
   nsIAtom* EventName() const
   {
     return mEventName;