Check same-thread Persistent<> read access.

third_party/WebKit/Source/modules/webaudio/MediaStreamAudioSourceNode.cpp

Index: third_party/WebKit/Source/modules/webaudio/MediaStreamAudioSourceNode.cpp
diff --git a/third_party/WebKit/Source/modules/webaudio/MediaStreamAudioSourceNode.cpp b/third_party/WebKit/Source/modules/webaudio/MediaStreamAudioSourceNode.cpp
index 04e14ae08945bcb6e03762a499a4dd7f46c6cde5..2541f7119914dda3b5bc6e693b25d3c138b3fb6c 100644
--- a/third_party/WebKit/Source/modules/webaudio/MediaStreamAudioSourceNode.cpp
+++ b/third_party/WebKit/Source/modules/webaudio/MediaStreamAudioSourceNode.cpp
@@ -36,14 +36,10 @@ namespace blink {
 
 MediaStreamAudioSourceHandler::MediaStreamAudioSourceHandler(
     AudioNode& node,
-    MediaStream& mediaStream,
-    MediaStreamTrack* audioTrack,
     std::unique_ptr<AudioSourceProvider> audioSourceProvider)
     : AudioHandler(NodeTypeMediaStreamAudioSource,
                    node,
                    node.context()->sampleRate()),
-      m_mediaStream(mediaStream),
-      m_audioTrack(audioTrack),
       m_audioSourceProvider(std::move(audioSourceProvider)),
       m_sourceNumberOfChannels(0) {
   // Default to stereo. This could change depending on the format of the
@@ -55,11 +51,9 @@ MediaStreamAudioSourceHandler::MediaStreamAudioSourceHandler(
 
 PassRefPtr<MediaStreamAudioSourceHandler> MediaStreamAudioSourceHandler::create(
     AudioNode& node,
-    MediaStream& mediaStream,
-    MediaStreamTrack* audioTrack,
     std::unique_ptr<AudioSourceProvider> audioSourceProvider) {
-  return adoptRef(new MediaStreamAudioSourceHandler(
-      node, mediaStream, audioTrack, std::move(audioSourceProvider)));
+  return adoptRef(
+      new MediaStreamAudioSourceHandler(node, std::move(audioSourceProvider)));
 }
 
 MediaStreamAudioSourceHandler::~MediaStreamAudioSourceHandler() {
@@ -104,8 +98,7 @@ void MediaStreamAudioSourceHandler::process(size_t numberOfFrames) {
     return;
   }
 
-  if (!getMediaStream() ||
-      m_sourceNumberOfChannels != outputBus->numberOfChannels()) {
+  if (m_sourceNumberOfChannels != outputBus->numberOfChannels()) {
     outputBus->zero();
     return;
   }
@@ -127,11 +120,10 @@ void MediaStreamAudioSourceHandler::process(size_t numberOfFrames) {
 MediaStreamAudioSourceNode::MediaStreamAudioSourceNode(
     BaseAudioContext& context,
     MediaStream& mediaStream,
-    MediaStreamTrack* audioTrack,
     std::unique_ptr<AudioSourceProvider> audioSourceProvider)
-    : AudioNode(context) {
+    : AudioNode(context), m_mediaStream(mediaStream) {
   setHandler(MediaStreamAudioSourceHandler::create(
-      *this, mediaStream, audioTrack, std::move(audioSourceProvider)));
+      *this, std::move(audioSourceProvider)));
 }
 
 MediaStreamAudioSourceNode* MediaStreamAudioSourceNode::create(
@@ -157,8 +149,8 @@ MediaStreamAudioSourceNode* MediaStreamAudioSourceNode::create(
   std::unique_ptr<AudioSourceProvider> provider =
       audioTrack->createWebAudioSource();
 
-  MediaStreamAudioSourceNode* node = new MediaStreamAudioSourceNode(
-      context, mediaStream, audioTrack, std::move(provider));
+  MediaStreamAudioSourceNode* node =
+      new MediaStreamAudioSourceNode(context, mediaStream, std::move(provider));
 
   if (!node)
     return nullptr;
@@ -180,6 +172,7 @@ MediaStreamAudioSourceNode* MediaStreamAudioSourceNode::create(
 }
 
 DEFINE_TRACE(MediaStreamAudioSourceNode) {
+  visitor->trace(m_mediaStream);
   AudioSourceProviderClient::trace(visitor);
   AudioNode::trace(visitor);
 }
@@ -190,7 +183,7 @@ MediaStreamAudioSourceNode::mediaStreamAudioSourceHandler() const {
 }
 
 MediaStream* MediaStreamAudioSourceNode::getMediaStream() const {
-  return mediaStreamAudioSourceHandler().getMediaStream();
+  return m_mediaStream;
 }
 
 void MediaStreamAudioSourceNode::setFormat(size_t numberOfChannels,