Disallow cross-thread Persistent<> read access.

third_party/WebKit/Source/modules/webaudio/AudioBufferSourceNode.h

 /*
  * Copyright (C) 2010, 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 106 matching lines @@
   inline bool renderSilenceAndFinishIfNotLooping(AudioBus*,
                                                  unsigned index,
                                                  size_t framesToProcess);
 
   // Clamps grain parameters to the duration of the given AudioBuffer.
   void clampGrainParameters(const AudioBuffer*);
 
   // m_buffer holds the sample data which this node outputs.
   // This Persistent doesn't make a reference cycle including
   // AudioBufferSourceNode.
-  Persistent<AudioBuffer> m_buffer;
+  // It is cross-thread, as it will be accessed by the audio and main threads.
+  CrossThreadPersistent<AudioBuffer> m_buffer;
 
   // Pointers for the buffer and destination.
   std::unique_ptr<const float* []> m_sourceChannels;
   std::unique_ptr<float* []> m_destinationChannels;
 
   RefPtr<AudioParamHandler> m_playbackRate;
   RefPtr<AudioParamHandler> m_detune;
 
   bool didSetLooping() const { return acquireLoad(&m_didSetLooping); }
   void setDidSetLooping(bool loop) {
@@ skipping 66 matching lines @@
  private:
   AudioBufferSourceNode(BaseAudioContext&);
 
   Member<AudioParam> m_playbackRate;
   Member<AudioParam> m_detune;
 };
 
 }  // namespace blink
 
 #endif  // AudioBufferSourceNode_h