Disallow cross-thread Persistent<> read access.

third_party/WebKit/Source/modules/webaudio/PannerNode.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 140 matching lines @@
                                   const FloatPoint3D& listenerPosition);
 
   void azimuthElevation(double* outAzimuth, double* outElevation);
   float distanceConeGain();
 
   bool isAzimuthElevationDirty() const { return m_isAzimuthElevationDirty; }
   bool isDistanceConeGainDirty() const { return m_isDistanceConeGainDirty; }
   void updateDirtyState();
 
   // This Persistent doesn't make a reference cycle including the owner
-  // PannerNode.
-  Persistent<AudioListener> m_listener;
+  // PannerNode. It is accessed by both audio and main thread.
+  CrossThreadPersistent<AudioListener> m_listener;
   std::unique_ptr<Panner> m_panner;
   unsigned m_panningModel;
   unsigned m_distanceModel;
 
   bool m_isAzimuthElevationDirty;
   bool m_isDistanceConeGainDirty;
 
   // Gain
   DistanceEffect m_distanceEffect;
   ConeEffect m_coneEffect;
@@ skipping 81 matching lines @@
   Member<AudioParam> m_positionZ;
 
   Member<AudioParam> m_orientationX;
   Member<AudioParam> m_orientationY;
   Member<AudioParam> m_orientationZ;
 };
 
 }  // namespace blink
 
 #endif  // PannerNode_h