Bug 1124261, part 2 - Make NS_NewXBLEventHandler infallible. r=smaug

dom/xbl/nsXBLEventHandler.cpp

@@ -160,30 +160,26 @@ nsXBLKeyEventHandler::HandleEvent(nsIDOMEvent* aEvent)
 
 ///////////////////////////////////////////////////////////////////////////////////
 
-nsresult
+already_AddRefed<nsXBLEventHandler>
 NS_NewXBLEventHandler(nsXBLPrototypeHandler* aHandler,
-                      nsIAtom* aEventType,
-                      nsXBLEventHandler** aResult)
+                      nsIAtom* aEventType)
 {
+  nsRefPtr<nsXBLEventHandler> handler;
+
   switch (nsContentUtils::GetEventClassID(nsDependentAtomString(aEventType))) {
     case eDragEventClass:
     case eMouseEventClass:
     case eMouseScrollEventClass:
     case eWheelEventClass:
     case eSimpleGestureEventClass:
-      *aResult = new nsXBLMouseEventHandler(aHandler);
+      handler = new nsXBLMouseEventHandler(aHandler);
       break;
     default:
-      *aResult = new nsXBLEventHandler(aHandler);
+      handler = new nsXBLEventHandler(aHandler);
       break;
   }
 
-  if (!*aResult)
-    return NS_ERROR_OUT_OF_MEMORY;
-
-  NS_ADDREF(*aResult);
-
-  return NS_OK;
+  return handler.forget();
 }
 
 nsresult

dom/xbl/nsXBLEventHandler.h

@@ -113,10 +113,9 @@ private:
   bool mUsingContentXBLScope;
 };
 
-nsresult
+already_AddRefed<nsXBLEventHandler>
 NS_NewXBLEventHandler(nsXBLPrototypeHandler* aHandler,
-                      nsIAtom* aEventType,
-                      nsXBLEventHandler** aResult);
+                      nsIAtom* aEventType);
 
 nsresult
 NS_NewXBLKeyEventHandler(nsIAtom* aEventType, uint8_t aPhase,

dom/xbl/nsXBLPrototypeHandler.h

@@ -132,8 +132,7 @@ public:
   nsXBLEventHandler* GetEventHandler()
   {
     if (!mHandler) {
-      NS_NewXBLEventHandler(this, mEventName, getter_AddRefs(mHandler));
-      // XXX Need to signal out of memory?
+      mHandler = NS_NewXBLEventHandler(this, mEventName);
     }
 
     return mHandler;