Inherit EventTarget interface instead of duplicating its code

Source/core/xml/XMLHttpRequest.h

 /*
  *  Copyright (C) 2003, 2006, 2008 Apple Inc. All rights reserved.
  *  Copyright (C) 2005, 2006 Alexey Proskuryakov <ap@nypop.com>
  *  Copyright (C) 2011 Google Inc. All rights reserved.
  *  Copyright (C) 2012 Intel Corporation
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Lesser General Public
  *  License as published by the Free Software Foundation; either
  *  version 2 of the License, or (at your option) any later version.
@@ skipping 30 matching lines @@
 
 class Blob;
 class Document;
 class DOMFormData;
 class ResourceRequest;
 class SecurityOrigin;
 class SharedBuffer;
 class TextResourceDecoder;
 class ThreadableLoader;
 
-class XMLHttpRequest : public ScriptWrappable, public RefCounted<XMLHttpRequest>, public EventTarget, private ThreadableLoaderClient, public ActiveDOMObject {
+class XMLHttpRequest : public EventTarget, public ScriptWrappable, public RefCounted<XMLHttpRequest>, private ThreadableLoaderClient, public ActiveDOMObject {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassRefPtr<XMLHttpRequest> create(ScriptExecutionContext*, PassRefPtr<SecurityOrigin> = 0);
     ~XMLHttpRequest();
 
     // These exact numeric values are important because JS expects them.
     enum State {
         UNSENT = 0,
         OPENED = 1,
         HEADERS_RECEIVED = 2,
@@ skipping 174 matching lines @@
 
     // An enum corresponding to the allowed string values for the responseType attribute.
     ResponseTypeCode m_responseTypeCode;
     Timer<XMLHttpRequest> m_protectionTimer;
     RefPtr<SecurityOrigin> m_securityOrigin;
 };
 
 } // namespace WebCore
 
 #endif // XMLHttpRequest_h