Guarantee a thread safety when accessing source location info in pannerNode.

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 98 matching lines @@
     // Sound cones - angles in degrees
     double coneInnerAngle() const { return m_coneEffect.innerAngle(); }
     void setConeInnerAngle(double angle) { m_coneEffect.setInnerAngle(angle); }
 
     double coneOuterAngle() const { return m_coneEffect.outerAngle(); }
     void setConeOuterAngle(double angle) { m_coneEffect.setOuterAngle(angle); }
 
     double coneOuterGain() const { return m_coneEffect.outerGain(); }
     void setConeOuterGain(double angle) { m_coneEffect.setOuterGain(angle); }
 
+    // It must be called on audio thread, currently called only process() in AudioBufferSourceNode.
     double dopplerRate();
 
     virtual double tailTime() const OVERRIDE { return m_panner ? m_panner->tailTime() : 0; }
     virtual double latencyTime() const OVERRIDE { return m_panner ? m_panner->latencyTime() : 0; }
 
 private:
     PannerNode(AudioContext*, float sampleRate);
 
     void calculateAzimuthElevation(double* outAzimuth, double* outElevation);
     // Returns the combined distance and cone gain attenuation.
     float calculateDistanceConeGain();
     double calculateDopplerRate();
 
     void azimuthElevation(double* outAzimuth, double* outElevation);
     float distanceConeGain();
 
     bool isAzimuthElevationDirty();
     bool isDistanceConeGainDirty();
     bool isDopplerRateDirty();
 
     // Notifies any AudioBufferSourceNodes connected to us either directly or indirectly about our existence.
     // This is in order to handle the pitch change necessary for the doppler shift.
     void notifyAudioSourcesConnectedToNode(AudioNode*, HashMap<AudioNode*, bool> &visitedNodes);
 
     void updateCachedListener();
     void updateCachedSourceLocationInfo();
 
     OwnPtr<Panner> m_panner;
     unsigned m_panningModel;
+    unsigned m_distanceModel;
 
     // Current source location information
     FloatPoint3D m_position;
     FloatPoint3D m_orientation;
     FloatPoint3D m_velocity;
 
     // Cached source location information
     FloatPoint3D m_cachedPosition;
     FloatPoint3D m_cachedOrientation;
     FloatPoint3D m_cachedVelocity;
@@ skipping 11 matching lines @@
     double m_cachedDopplerRate;
 
     // Cached listener parameters after processing.
     RefPtr<AudioListener> m_cachedListener;
 
     RefPtr<HRTFDatabaseLoader> m_hrtfDatabaseLoader;
 
     // AudioContext's connection count
     unsigned m_connectionCount;
 
-    // Synchronize process() and setPanningModel() which can change the panner.
-    mutable Mutex m_pannerLock;
+    // Synchronize process() with setting of the panning model, distance model and caching of the source location/orientation info.
+    mutable Mutex m_processLock;
 };
 
 } // namespace WebCore
 
 #endif // PannerNode_h