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

Source/modules/webaudio/MediaStreamAudioSourceNode.cpp

Index: Source/modules/webaudio/MediaStreamAudioSourceNode.cpp
diff --git a/Source/modules/webaudio/MediaStreamAudioSourceNode.cpp b/Source/modules/webaudio/MediaStreamAudioSourceNode.cpp
index 617f6f9606dcdeb3d51a5613bef0401bb8321bc8..3fbf17d53cdcc25f4d7abf6ec12b1656161afc5e 100644
--- a/Source/modules/webaudio/MediaStreamAudioSourceNode.cpp
+++ b/Source/modules/webaudio/MediaStreamAudioSourceNode.cpp
@@ -35,14 +35,15 @@
 
 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)
 {