Make reduction value of dynamics compressor zero when no sources are connected

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 102 matching lines @@
     // The AudioNodeInput(s) (if any) will already have their input data available when process() is called.
     // Subclasses will take this input data and put the results in the AudioBus(s) of its AudioNodeOutput(s) (if any).
     // Called from context's audio thread.
     virtual void process(size_t framesToProcess) = 0;
 
     // No significant resources should be allocated until initialize() is called.
     // Processing may not occur until a node is initialized.
     virtual void initialize();
     virtual void uninitialize();
 
+    // Clear internal state when the node is deactivated. This prevents the node
+    // from providing the incorrect data based on the last-known data inside.

[Raymond Toy, 2014/10/21 20:47:57]

"deactivated" -> "disabled". I think this comment is not quite right. Perhaps
something like:

Clear internal state when the node is disabled.  When a node is disabled, it is
no longer pulled so any internal state is never updated. But some nodes
(DynamicsCompressorNode) have internal state that is still accessible by the
user.  Update the internal state as if the node were still connected but
processing all zeroes. This gives a consistent view to the user.

[hongchan, 2014/10/21 20:58:54]

Acknowledged and replaced.

+    virtual void clearInternalState();

[Raymond Toy, 2014/10/21 20:47:57]

If the comment above is used, perhaps this function should be called
updateInternalStateWhenDisabled instead of clearInternalState?

[hongchan, 2014/10/21 20:58:54]

Good to be more descriptive. But I think this method can be used in other places
where require the reset the internal state. updateInternalState() should be
okay. What do you think?

[Raymond Toy, 2014/10/21 21:05:54]

Hard to say what the future holds. Ok for now, as long as we are careful not to
overuse this to clear internal state.  The comment, however, makes it clear what
this method is supposed to do and when.

+
     bool isInitialized() const { return m_isInitialized; }
 
     unsigned numberOfInputs() const { return m_inputs.size(); }
     unsigned numberOfOutputs() const { return m_outputs.size(); }
 
     AudioNodeInput* input(unsigned);
     AudioNodeOutput* output(unsigned);
 
     // Called from main thread by corresponding JavaScript methods.
     virtual void connect(AudioNode*, unsigned outputIndex, unsigned inputIndex, ExceptionState&);
@@ skipping 93 matching lines @@
     ChannelCountMode m_channelCountMode;
     AudioBus::ChannelInterpretation m_channelInterpretation;
     // The new channel count mode that will be used to set the actual mode in the pre or post
     // rendering phase.
     ChannelCountMode m_newChannelCountMode;
 };
 
 } // namespace blink
 
 #endif // AudioNode_h