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 158 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() and setters panningModel, distanceModel and source location info.

[Raymond Toy, 2014/03/13 21:37:46]

Update comment:

// Synchronize process() with setting of the panning model, distance model, and
caching of the source location/orientation info.

[KhNo, 2014/03/14 10:39:58]

Done.

[Raymond Toy, 2014/03/14 22:30:36]

Please use this comment. Your replacement is not quite the same and doesn't read
quite right.

[KhNo, 2014/03/15 04:58:16]

Done.

+    mutable Mutex m_processLock;

[Raymond Toy, 2014/03/13 21:37:46]

Why change the name?

[KhNo, 2014/03/14 10:39:58]

Previous code only has locked for m_panner which is for panningModel.
Now, there are additional things have to lock such as distanceModel, location
info...
In General, other source about web audio named m_processLock when there is
something to lock during excute process().

[Raymond Toy, 2014/03/14 22:30:36]

Ok.

 };
 
 } // namespace WebCore
 
 #endif // PannerNode_h