Remove leak of objects between isolated worlds on custom events.

Source/bindings/v8/V8HiddenPropertyName.h

 /*
  * Copyright (C) 2012 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 25 matching lines @@
 namespace WebCore {
 
 #define V8_HIDDEN_PROPERTIES(V) \
     V(adaptorFunctionPeer) \
     V(attributeListener) \
     V(callback) \
     V(customElementAttributeChanged) \
     V(customElementCreated) \
     V(customElementEnteredDocument) \
     V(customElementLeftDocument) \
+    V(data) \
     V(detail) \
     V(document) \
     V(event) \
     V(isCustomElementInterfacePrototypeObject) \
     V(listener) \
     V(name) \
     V(namespaceURI) \
     V(scriptState) \
     V(sleepFunction) \
     V(state) \
@@ skipping 13 matching lines @@
 private:
     static void createString(const char* key, v8::Persistent<v8::String>* handle);
 #define V8_DECLARE_FIELD(name) v8::Persistent<v8::String> m_##name;
     V8_HIDDEN_PROPERTIES(V8_DECLARE_FIELD);
 #undef V8_DECLARE_FIELD
 };
 
 }
 
 #endif // V8HiddenPropertyName_h