Defer changes to the channel count mode to the pre or post-render phase

Source/modules/webaudio/AudioNode.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 165 matching lines @@
     String channelInterpretation();
     void setChannelInterpretation(const String&, ExceptionState&);
 
     ChannelCountMode internalChannelCountMode() const { return m_channelCountMode; }
     AudioBus::ChannelInterpretation internalChannelInterpretation() const { return m_channelInterpretation; }
 
     // EventTarget
     virtual const AtomicString& interfaceName() const OVERRIDE FINAL;
     virtual ExecutionContext* executionContext() const OVERRIDE FINAL;
 
+    void updateChannelCountMode();
+
     virtual void trace(Visitor*) OVERRIDE;
 
 protected:
     // Inputs and outputs must be created before the AudioNode is initialized.
     void addInput();
     void addOutput(AudioNodeOutput*);
 
     // Called by processIfNecessary() to cause all parts of the rendering graph connected to us to process.
     // Each rendering quantum, the audio data for each of the AudioNode's inputs will be available after this method is called.
     // Called from context's audio thread.
@@ skipping 16 matching lines @@
     volatile int m_connectionRefCount;
 
     bool m_isDisabled;
 
 #if DEBUG_AUDIONODE_REFERENCES
     static bool s_isNodeCountInitialized;
     static int s_nodeCount[NodeTypeEnd];
 #endif
     static unsigned s_instanceCount;
 
+    // The new channel count mode that will be used to set the actual mode in the pre or post
+    // rendering phase.
+    ChannelCountMode m_newChannelCountMode;
 protected:
     unsigned m_channelCount;
     ChannelCountMode m_channelCountMode;
     AudioBus::ChannelInterpretation m_channelInterpretation;
 };
 
 } // namespace blink
 
 #endif // AudioNode_h