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

Source/core/events/FocusEvent.cpp

 /*
  * 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:
  * 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 48 matching lines @@
     ScriptWrappable::init(this);
 }
 
 FocusEvent::FocusEvent(const AtomicString& type, const FocusEventInit& initializer)
     : UIEvent(type, initializer)
     , m_relatedTarget(initializer.relatedTarget)
 {
     ScriptWrappable::init(this);
 }
 
+void FocusEvent::trace(Visitor* visitor)
+{
+    UIEvent::trace(visitor);
+}
+
 PassRefPtr<FocusEventDispatchMediator> FocusEventDispatchMediator::create(PassRefPtr<FocusEvent> focusEvent)
 {
     return adoptRef(new FocusEventDispatchMediator(focusEvent));
 }
 
 FocusEventDispatchMediator::FocusEventDispatchMediator(PassRefPtr<FocusEvent> focusEvent)
     : EventDispatchMediator(focusEvent)
 {
 }
 
@@ skipping 45 matching lines @@
 {
 }
 
 bool FocusOutEventDispatchMediator::dispatchEvent(EventDispatcher* dispatcher) const
 {
     event()->eventPath().adjustForRelatedTarget(dispatcher->node(), event()->relatedTarget());
     return EventDispatchMediator::dispatchEvent(dispatcher);
 }
 
 } // namespace WebCore