Fix data race in AudioDestination.cpp

third_party/WebKit/Source/platform/audio/AudioDestination.h

Index: third_party/WebKit/Source/platform/audio/AudioDestination.h
diff --git a/third_party/WebKit/Source/platform/audio/AudioDestination.h b/third_party/WebKit/Source/platform/audio/AudioDestination.h
index 64797f225cfe21ea6e33bd4cbc787e338fb64ed7..f058d818f0bd10b90df575cef02d4b1e867c9764 100644
--- a/third_party/WebKit/Source/platform/audio/AudioDestination.h
+++ b/third_party/WebKit/Source/platform/audio/AudioDestination.h
@@ -106,18 +106,20 @@ class PLATFORM_EXPORT AudioDestination : public WebAudioDevice::RenderCallback {
 
   bool IsRenderingThread();
 
+  // Accessed by the main thread.
   std::unique_ptr<WebAudioDevice> web_audio_device_;
   const unsigned number_of_output_channels_;
   size_t callback_buffer_size_;
   bool is_playing_;
 
-  // Rendering thread for WebAudio graph.
-  std::unique_ptr<WebThread> rendering_thread_;
-
-  // Accessed by both threads: resolves the buffer size mismatch between the
-  // WebAudio engine and the callback function from the actual audio device.
+  // Accessed by device and rendering threads: resolves the buffer size mismatch
+  // between the WebAudio engine and the callback function from the actual audio
+  // device.
   std::unique_ptr<PushPullFIFO> fifo_;
 
+  // Accessed by the device thread. Rendering thread for WebAudio graph.
+  std::unique_ptr<WebThread> rendering_thread_;
+
   // Accessed by device thread: to pass the data from FIFO to the device.
   RefPtr<AudioBus> output_bus_;