Implement StereoPannerNode for robust stereo panning

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 59 matching lines @@
         NodeTypeUnknown,
         NodeTypeDestination,
         NodeTypeOscillator,
         NodeTypeAudioBufferSource,
         NodeTypeMediaElementAudioSource,
         NodeTypeMediaStreamAudioDestination,
         NodeTypeMediaStreamAudioSource,
         NodeTypeJavaScript,
         NodeTypeBiquadFilter,
         NodeTypePanner,
+        NodeTypeStereoPanner,
         NodeTypeConvolver,
         NodeTypeDelay,
         NodeTypeGain,
         NodeTypeChannelSplitter,
         NodeTypeChannelMerger,
         NodeTypeAnalyser,
         NodeTypeDynamicsCompressor,
         NodeTypeWaveShaper,
         NodeTypeEnd
     };
@@ skipping 144 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