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

Source/modules/webaudio/AudioContext.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 133 matching lines @@
     void registerLiveNode(AudioNode&);
 
     // AudioContext can pull node(s) at the end of each render quantum even when they are not connected to any downstream nodes.
     // These two methods are called by the nodes who want to add/remove themselves into/from the automatic pull lists.
     void addAutomaticPullNode(AudioNode*);
     void removeAutomaticPullNode(AudioNode*);
 
     // Called right before handlePostRenderTasks() to handle nodes which need to be pulled even when they are not connected to anything.
     void processAutomaticPullNodes(size_t framesToProcess);
 
+    // Keep track of AudioNode's that have their channel count mode changed. We process the changes
+    // in the post rendering phase.
+    void addChangedChannelCountMode(AudioNode*);
+    void removeChangedChannelCountMode(AudioNode*);
+    void updateChangedChannelCountMode();
+
     // Keeps track of the number of connections made.
     void incrementConnectionCount()
     {
         ASSERT(isMainThread());
         m_connectionCount++;
     }
 
     unsigned connectionCount() const { return m_connectionCount; }
 
     //
@@ skipping 171 matching lines @@
     // we cannot use HeapVectors.
     GC_PLUGIN_IGNORE("http://crbug.com/404527")
     Vector<AudioNode*> m_deferredBreakConnectionList;
 
     Member<AudioBuffer> m_renderTarget;
 
     bool m_isOfflineContext;
 
     AsyncAudioDecoder m_audioDecoder;
 
+    // Collection of nodes where the channel count mode has changed. We want the channel count mode
+    // to change in the pre- or post-rendering phase so as not to disturb the running audio thread.
+    GC_PLUGIN_IGNORE("http://crbug.com/404527")
+    HashSet<AudioNode*> m_deferredCountModeChange;
+
     // 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 // AudioContext_h