Remove modules/webaudio/MediaElementAudioSourceNode.h dependency from core.

Source/modules/webaudio/MediaElementAudioSourceNode.h

 /*
  * Copyright (C) 2011, 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 35 matching lines @@
     virtual ~MediaElementAudioSourceNode();
 
     HTMLMediaElement* mediaElement() { return m_mediaElement.get(); }
 
     // AudioNode
     virtual void process(size_t framesToProcess) OVERRIDE;
 
     // AudioSourceProviderClient
     virtual void setFormat(size_t numberOfChannels, float sampleRate) OVERRIDE;
 
-    void lock();
-    void unlock();
+    virtual void lock() OVERRIDE;
+    virtual void unlock() OVERRIDE;
 
 private:
     MediaElementAudioSourceNode(AudioContext*, HTMLMediaElement*);
 
     // As an audio source, we will never propagate silence.
     virtual bool propagatesSilence() const OVERRIDE { return false; }
 
     RefPtr<HTMLMediaElement> m_mediaElement;
     Mutex m_processLock;
 
     unsigned m_sourceNumberOfChannels;
     double m_sourceSampleRate;
 
     OwnPtr<MultiChannelResampler> m_multiChannelResampler;
 };
 
 } // namespace WebCore
 
 #endif // ENABLE(WEB_AUDIO)
 
 #endif // MediaElementAudioSourceNode_h