Make Event RefCountedGarbageCollected and implement trace() methods to the Event hierarcy

Source/core/storage/StorageEvent.h

 /*
  * Copyright (C) 2008, 2009 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 46 matching lines @@
     Storage* storageArea() const { return m_storageArea.get(); }
     Storage* storageArea(bool& isNull) const { isNull = !m_storageArea; return m_storageArea.get(); }
 
     void initStorageEvent(const AtomicString& type, bool canBubble, bool cancelable, const String& key, const String& oldValue, const String& newValue, const String& url, Storage* storageArea);
 
     // Needed once we support init<blank>EventNS
     // void initStorageEventNS(in DOMString namespaceURI, in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in DOMString keyArg, in DOMString oldValueArg, in DOMString newValueArg, in DOMString urlArg, Storage storageAreaArg);
 
     virtual const AtomicString& interfaceName() const OVERRIDE;
 
+    virtual void trace(Visitor*) OVERRIDE;
+
 private:
     StorageEvent();
     StorageEvent(const AtomicString& type, const String& key, const String& oldValue, const String& newValue, const String& url, Storage* storageArea);
     StorageEvent(const AtomicString&, const StorageEventInit&);
 
     String m_key;
     String m_oldValue;
     String m_newValue;
     String m_url;
     RefPtr<Storage> m_storageArea;
 };
 
 } // namespace WebCore
 
 #endif // StorageEvent_h