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

Source/core/events/KeyboardEvent.cpp

 /**
  * Copyright (C) 2001 Peter Kelly (pmk@post.com)
  * Copyright (C) 2001 Tobias Anton (anton@stud.fbi.fh-darmstadt.de)
  * Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2003, 2005, 2006, 2007 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 199 matching lines @@
     return true;
 }
 
 int KeyboardEvent::which() const
 {
     // Netscape's "which" returns a virtual key code for keydown and keyup, and a character code for keypress.
     // That's exactly what IE's "keyCode" returns. So they are the same for keyboard events.
     return keyCode();
 }
 
+void KeyboardEvent::trace(Visitor* visitor)
+{
+    UIEventWithKeyState::trace(visitor);
+}
+
 PassRefPtr<KeyboardEventDispatchMediator> KeyboardEventDispatchMediator::create(PassRefPtr<KeyboardEvent> event)
 {
     return adoptRef(new KeyboardEventDispatchMediator(event));
 }
 
 KeyboardEventDispatchMediator::KeyboardEventDispatchMediator(PassRefPtr<KeyboardEvent> event)
     : EventDispatchMediator(event)
 {
 }
 
 bool KeyboardEventDispatchMediator::dispatchEvent(EventDispatcher* dispatcher) const
 {
     // Make sure not to return true if we already took default action while handling the event.
     return EventDispatchMediator::dispatchEvent(dispatcher) && !event()->defaultHandled();
 }
 
 } // namespace WebCore