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

Source/core/events/SecurityPolicyViolationEvent.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:
  * 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 54 matching lines @@
     const String& violatedDirective() const { return m_violatedDirective; }
     const String& effectiveDirective() const { return m_effectiveDirective; }
     const String& originalPolicy() const { return m_originalPolicy; }
     const String& sourceFile() const { return m_sourceFile; }
     int lineNumber() const { return m_lineNumber; }
     int columnNumber() const { return m_columnNumber; }
     int statusCode() const { return m_statusCode; }
 
     virtual const AtomicString& interfaceName() const OVERRIDE { return EventNames::SecurityPolicyViolationEvent; }
 
+    virtual void trace(Visitor* visitor) OVERRIDE { Event::trace(visitor); }
+
 private:
     SecurityPolicyViolationEvent()
     {
         ScriptWrappable::init(this);
     }
 
     SecurityPolicyViolationEvent(const AtomicString& type, const SecurityPolicyViolationEventInit& initializer)
         : Event(type, initializer)
         , m_documentURI(initializer.documentURI)
         , m_referrer(initializer.referrer)
@@ skipping 17 matching lines @@
     String m_originalPolicy;
     String m_sourceFile;
     int m_lineNumber;
     int m_columnNumber;
     int m_statusCode;
 };
 
 } // namespace WebCore
 
 #endif // SecurityPolicyViolationEvent_h