Inherit EventTarget interface instead of duplicating its code

Source/modules/mediasource/SourceBuffer.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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 28 matching lines @@
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
 #include "wtf/text/WTFString.h"
 
 namespace WebCore {
 class GenericEventQueue;
 class MediaSource;
 class SourceBufferPrivate;
 class TimeRanges;
 
-class SourceBuffer : public RefCounted<SourceBuffer>, public ActiveDOMObject, public EventTarget, public ScriptWrappable {
+class SourceBuffer : public EventTarget, public RefCounted<SourceBuffer>, public ActiveDOMObject, public ScriptWrappable {
 public:
     static PassRefPtr<SourceBuffer> create(PassOwnPtr<SourceBufferPrivate>, MediaSource*, GenericEventQueue*);
 
     virtual ~SourceBuffer();
 
     // SourceBuffer.idl methods
     bool updating() const { return m_updating; }
     PassRefPtr<TimeRanges> buffered(ExceptionCode&) const;
     double timestampOffset() const;
     void setTimestampOffset(double, ExceptionCode&);
@@ skipping 39 matching lines @@
     bool m_updating;
     double m_timestampOffset;
 
     Vector<unsigned char> m_pendingAppendData;
     Timer<SourceBuffer> m_appendBufferTimer;
 };
 
 } // namespace WebCore
 
 #endif