Keep a strong handle to an event listener during handleEvent

Source/bindings/dart/DartEventListener.h

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 53 matching lines @@
     static EventListener* toNative(Dart_NativeArguments args, int idx, Dart_Handle& exception)
     {
         Dart_Handle object = Dart_GetNativeArgument(args, idx);
         return toNative(object, exception);
     }
 
 private:
     DartEventListener();
 
     static DartEventListener* createOrFetch(Dart_Handle listener);
-    Dart_Handle callListenerFunction(ScriptExecutionContext*, Dart_Handle dartEvent, Event*);
+    Dart_Handle callListenerFunction(ScriptExecutionContext*, Dart_Handle listener, Dart_Handle dartEvent);
 
     static void weakCallback(Dart_WeakPersistentHandle, void* peer);
 
     Dart_Isolate m_isolate;
     Dart_WeakPersistentHandle m_listener;
     // FIXME: investigate why m_worldContext is needed in v8, extensions?
 };
 
 }
 
 #endif // DartEventListener_h