Inherit EventTarget interface instead of duplicating its code

Source/modules/mediastream/RTCPeerConnection.h

 /*
  * Copyright (C) 2012 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
@@ skipping 39 matching lines @@
 class RTCDTMFSender;
 class RTCDataChannel;
 class RTCErrorCallback;
 class RTCSessionDescription;
 class RTCSessionDescriptionCallback;
 class RTCStatsCallback;
 class VoidCallback;
 
 typedef int ExceptionCode;
 
-class RTCPeerConnection : public RefCounted<RTCPeerConnection>, public ScriptWrappable, public RTCPeerConnectionHandlerClient, public EventTarget, public ActiveDOMObject {
+class RTCPeerConnection : public EventTarget, public RefCounted<RTCPeerConnection>, public ScriptWrappable, public RTCPeerConnectionHandlerClient, public ActiveDOMObject {
 public:
     static PassRefPtr<RTCPeerConnection> create(ScriptExecutionContext*, const Dictionary& rtcConfiguration, const Dictionary& mediaConstraints, ExceptionCode&);
     ~RTCPeerConnection();
 
     void createOffer(PassRefPtr<RTCSessionDescriptionCallback>, PassRefPtr<RTCErrorCallback>, const Dictionary& mediaConstraints, ExceptionCode&);
 
     void createAnswer(PassRefPtr<RTCSessionDescriptionCallback>, PassRefPtr<RTCErrorCallback>, const Dictionary& mediaConstraints, ExceptionCode&);
 
     void setLocalDescription(PassRefPtr<RTCSessionDescription>, PassRefPtr<VoidCallback>, PassRefPtr<RTCErrorCallback>, ExceptionCode&);
     PassRefPtr<RTCSessionDescription> localDescription(ExceptionCode&);
@@ skipping 89 matching lines @@
 
     Timer<RTCPeerConnection> m_scheduledEventTimer;
     Vector<RefPtr<Event> > m_scheduledEvents;
 
     bool m_stopped;
 };
 
 } // namespace WebCore
 
 #endif // RTCPeerConnection_h