Remove unnecessary attribute "gain" in AudioBuffer and AudioBufferSourceNode interfaces

Source/modules/webaudio/AudioBuffer.h

 /*
  * Copyright (C) 2010 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 41 matching lines @@
     size_t length() const { return m_length; }
     double duration() const { return length() / static_cast<double>(sampleRate()); }
     float sampleRate() const { return m_sampleRate; }
 
     // Channel data access
     unsigned numberOfChannels() const { return m_channels.size(); }
     PassRefPtr<Float32Array> getChannelData(unsigned channelIndex, ExceptionState&);
     Float32Array* getChannelData(unsigned channelIndex);
     void zero();
 
-    // Scalar gain
-    double gain() const { return m_gain; }
-    void setGain(double gain) { m_gain = gain; }
-
     static float minAllowedSampleRate();
     static float maxAllowedSampleRate();
 protected:
     AudioBuffer(unsigned numberOfChannels, size_t numberOfFrames, float sampleRate);
     explicit AudioBuffer(AudioBus*);
     bool createdSuccessfully(unsigned desiredNumberOfChannels) const;
 
-    double m_gain; // scalar gain
     float m_sampleRate;
     size_t m_length;
 
     Vector<RefPtr<Float32Array> > m_channels;
 };
 
 } // namespace WebCore
 
 #endif // AudioBuffer_h