create one WebAudioSource for each CreateMediaStreamSource() call.

Source/modules/webaudio/MediaStreamAudioSourceNode.h

Index: Source/modules/webaudio/MediaStreamAudioSourceNode.h
diff --git a/Source/modules/webaudio/MediaStreamAudioSourceNode.h b/Source/modules/webaudio/MediaStreamAudioSourceNode.h
index e139ef73bba38c78db600695c4fcea7eb8338d1f..96f0b5d0e4092be309bc8b379365919edaf1cc93 100644
--- a/Source/modules/webaudio/MediaStreamAudioSourceNode.h
+++ b/Source/modules/webaudio/MediaStreamAudioSourceNode.h
@@ -41,7 +41,7 @@ class AudioContext;
 
 class MediaStreamAudioSourceNode FINAL : public AudioSourceNode, public AudioSourceProviderClient {
 public:
-    static PassRefPtr<MediaStreamAudioSourceNode> create(AudioContext*, MediaStream*, MediaStreamTrack*, AudioSourceProvider*);
+    static PassRefPtr<MediaStreamAudioSourceNode> create(AudioContext*, MediaStream*, MediaStreamTrack*, PassOwnPtr<AudioSourceProvider>);
 
     virtual ~MediaStreamAudioSourceNode();
 
@@ -53,17 +53,17 @@ public:
     // AudioSourceProviderClient
     virtual void setFormat(size_t numberOfChannels, float sampleRate) OVERRIDE;
 
-    AudioSourceProvider* audioSourceProvider() const { return m_audioSourceProvider; }
+    AudioSourceProvider* audioSourceProvider() const { return m_audioSourceProvider.get(); }
 
 private:
-    MediaStreamAudioSourceNode(AudioContext*, MediaStream*, MediaStreamTrack*, AudioSourceProvider*);
+    MediaStreamAudioSourceNode(AudioContext*, MediaStream*, MediaStreamTrack*, PassOwnPtr<AudioSourceProvider>);
 
     // As an audio source, we will never propagate silence.
     virtual bool propagatesSilence() const OVERRIDE { return false; }
 
     RefPtr<MediaStream> m_mediaStream;
     RefPtr<MediaStreamTrack> m_audioTrack;
-    AudioSourceProvider* m_audioSourceProvider;
+    OwnPtr<AudioSourceProvider> m_audioSourceProvider;
 
     Mutex m_processLock;