Fixed the crash in the wbaudio source provider when the audio track is going away.

Source/modules/webaudio/MediaStreamAudioSourceNode.cpp

 /*
  * 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 17 matching lines @@
 
 #include "modules/webaudio/MediaStreamAudioSourceNode.h"
 
 #include "platform/Logging.h"
 #include "modules/webaudio/AudioContext.h"
 #include "modules/webaudio/AudioNodeOutput.h"
 #include "wtf/Locker.h"
 
 namespace WebCore {
 
-PassRefPtr<MediaStreamAudioSourceNode> MediaStreamAudioSourceNode::create(AudioContext* context, MediaStream* mediaStream, AudioSourceProvider* audioSourceProvider)
+PassRefPtr<MediaStreamAudioSourceNode> MediaStreamAudioSourceNode::create(AudioContext* context, MediaStream* mediaStream, MediaStreamTrack* audioTrack, AudioSourceProvider* audioSourceProvider)
 {
-    return adoptRef(new MediaStreamAudioSourceNode(context, mediaStream, audioSourceProvider));
+    return adoptRef(new MediaStreamAudioSourceNode(context, mediaStream, audioTrack, audioSourceProvider));
 }
 
-MediaStreamAudioSourceNode::MediaStreamAudioSourceNode(AudioContext* context, MediaStream* mediaStream, AudioSourceProvider* audioSourceProvider)
+MediaStreamAudioSourceNode::MediaStreamAudioSourceNode(AudioContext* context, MediaStream* mediaStream, MediaStreamTrack* audioTrack, AudioSourceProvider* audioSourceProvider)
     : AudioSourceNode(context, context->sampleRate())
     , m_mediaStream(mediaStream)
+    , m_audioTrack(audioTrack)
     , m_audioSourceProvider(audioSourceProvider)
     , m_sourceNumberOfChannels(0)
 {
     ScriptWrappable::init(this);
     // Default to stereo. This could change depending on the format of the MediaStream's audio track.
     addOutput(adoptPtr(new AudioNodeOutput(this, 2)));
 
     setNodeType(NodeTypeMediaStreamAudioSource);
 
     initialize();
@@ skipping 56 matching lines @@
     }
 }
 
 void MediaStreamAudioSourceNode::reset()
 {
 }
 
 } // namespace WebCore
 
 #endif // ENABLE(WEB_AUDIO)