Inherit EventTarget interface instead of duplicating its code

Source/modules/mediastream/RTCDTMFSender.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 21 matching lines @@
 #include "core/platform/Timer.h"
 #include "core/platform/mediastream/RTCDTMFSenderHandlerClient.h"
 #include "wtf/RefCounted.h"
 
 namespace WebCore {
 
 class MediaStreamTrack;
 class RTCPeerConnectionHandler;
 class RTCDTMFSenderHandler;
 
-class RTCDTMFSender : public RefCounted<RTCDTMFSender>, public ScriptWrappable, public EventTarget, public RTCDTMFSenderHandlerClient, public ActiveDOMObject {
+class RTCDTMFSender : public EventTarget, public RefCounted<RTCDTMFSender>, public ScriptWrappable, public RTCDTMFSenderHandlerClient, public ActiveDOMObject {
 public:
     static PassRefPtr<RTCDTMFSender> create(ScriptExecutionContext*, RTCPeerConnectionHandler*, PassRefPtr<MediaStreamTrack>, ExceptionCode&);
     ~RTCDTMFSender();
 
     bool canInsertDTMF() const;
     MediaStreamTrack* track() const;
     String toneBuffer() const;
     long duration() const { return m_duration; }
     long interToneGap() const { return m_interToneGap; }
 
@@ skipping 37 matching lines @@
 
     bool m_stopped;
 
     Timer<RTCDTMFSender> m_scheduledEventTimer;
     Vector<RefPtr<Event> > m_scheduledEvents;
 };
 
 } // namespace WebCore
 
 #endif // RTCDTMFSender_h