Defer changes to channelInterpretation to pre/post rendering.

third_party/WebKit/Source/modules/webaudio/AbstractAudioContext.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 214 matching lines @@
     DeferredTaskHandler& deferredTaskHandler() const { return *m_deferredTaskHandler; }
     //
     // Thread Safety and Graph Locking:
     //
     // The following functions call corresponding functions of
     // DeferredTaskHandler.
     bool isAudioThread() const { return deferredTaskHandler().isAudioThread(); }
     void lock() { deferredTaskHandler().lock(); }
     bool tryLock() { return deferredTaskHandler().tryLock(); }
     void unlock() { deferredTaskHandler().unlock(); }
-#if ENABLE(ASSERT)
     // Returns true if this thread owns the context's lock.
     bool isGraphOwner() { return deferredTaskHandler().isGraphOwner(); }
-#endif

[hongchan, 2016/05/26 21:00:57]

What is the meaning of this? Perhaps there was a time that ASSERT was used
rarely?

[Raymond Toy, 2016/05/26 21:06:58]

I discovered this just now.  Previously ASSERT(...) would generate no code if
asserts were disabled.  But DCHECK always emits something (so variables in
DCHECK are used), so now we need to have isGraphOwner defined so that DCHECK is
valid.

[Nico, 2016/05/27 13:09:33]

That doesn't sound right. DCHECK() compiles to nothing if dchecks are not
enabled.

     using AutoLocker = DeferredTaskHandler::AutoLocker;
 
     // Returns the maximum numuber of channels we can support.
     static unsigned maxNumberOfChannels() { return MaxNumberOfChannels;}
 
     // EventTarget
     const AtomicString& interfaceName() const final;
     ExecutionContext* getExecutionContext() const final;
 
     DEFINE_ATTRIBUTE_EVENT_LISTENER(statechange);
@@ skipping 115 matching lines @@
     Member<PeriodicWave> m_periodicWaveTriangle;
 
     // This is considering 32 is large enough for multiple channels audio.
     // It is somewhat arbitrary and could be increased if necessary.
     enum { MaxNumberOfChannels = 32 };
 };
 
 } // namespace blink
 
 #endif // AbstractAudioContext_h