Remove unnecessary attribute "gain" in AudioBuffer and AudioBufferSourceNode interfaces

Source/modules/webaudio/AudioBuffer.cpp

 /*
  * 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 64 matching lines @@
 
     return nullptr;
 }
 
 bool AudioBuffer::createdSuccessfully(unsigned desiredNumberOfChannels) const
 {
     return numberOfChannels() == desiredNumberOfChannels;
 }
 
 AudioBuffer::AudioBuffer(unsigned numberOfChannels, size_t numberOfFrames, float sampleRate)
-    : m_gain(1.0)
-    , m_sampleRate(sampleRate)
+    : m_sampleRate(sampleRate)
     , m_length(numberOfFrames)
 {
     ScriptWrappable::init(this);
     m_channels.reserveCapacity(numberOfChannels);
 
     for (unsigned i = 0; i < numberOfChannels; ++i) {
         RefPtr<Float32Array> channelDataArray = Float32Array::create(m_length);
         // If the channel data array could not be created, just return. The caller will need to
         // check that the desired number of channels were created.
         if (!channelDataArray) {
             return;
         }
 
         channelDataArray->setNeuterable(false);
         m_channels.append(channelDataArray);
     }
 }
 
 AudioBuffer::AudioBuffer(AudioBus* bus)
-    : m_gain(1.0)
-    , m_sampleRate(bus->sampleRate())
+    : m_sampleRate(bus->sampleRate())
     , m_length(bus->length())
 {
     ScriptWrappable::init(this);
     // Copy audio data from the bus to the Float32Arrays we manage.
     unsigned numberOfChannels = bus->numberOfChannels();
     m_channels.reserveCapacity(numberOfChannels);
     for (unsigned i = 0; i < numberOfChannels; ++i) {
         RefPtr<Float32Array> channelDataArray = Float32Array::create(m_length);
         // If the channel data array could not be created, just return. The caller will need to
         // check that the desired number of channels were created.
@@ skipping 29 matching lines @@
 {
     for (unsigned i = 0; i < m_channels.size(); ++i) {
         if (getChannelData(i))
             getChannelData(i)->zeroRange(0, length());
     }
 }
 
 } // namespace WebCore
 
 #endif // ENABLE(WEB_AUDIO)