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

Source/core/css/CSSFontFaceLoadEvent.h

 /*
  * Copyright (C) 2013 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 49 matching lines @@
     {
         return adoptRef<CSSFontFaceLoadEvent>(new CSSFontFaceLoadEvent(type, fontfaces));
     }
 
     virtual ~CSSFontFaceLoadEvent();
 
     FontFaceArray fontfaces() const { return m_fontfaces; }
 
     virtual const AtomicString& interfaceName() const OVERRIDE;
 
+    virtual void trace(Visitor*) OVERRIDE;
+
 private:
     CSSFontFaceLoadEvent();
     CSSFontFaceLoadEvent(const AtomicString&, const FontFaceArray&);
     CSSFontFaceLoadEvent(const AtomicString&, const CSSFontFaceLoadEventInit&);
 
     FontFaceArray m_fontfaces;
 };
 
 } // namespace WebCore
 
 #endif // CSSFontFaceLoadEvent_h