Complete the implementation of up/down-mixing rules for AudioNode

third_party/WebKit/Source/platform/audio/AudioBus.h

Index: third_party/WebKit/Source/platform/audio/AudioBus.h
diff --git a/third_party/WebKit/Source/platform/audio/AudioBus.h b/third_party/WebKit/Source/platform/audio/AudioBus.h
index 5657f4f704597a487dfbc43edd65c7288fc59f09..eb202360bc8e32f4efd43318abb2217b32e8664f 100644
--- a/third_party/WebKit/Source/platform/audio/AudioBus.h
+++ b/third_party/WebKit/Source/platform/audio/AudioBus.h
@@ -151,11 +151,12 @@ protected:
 
     AudioBus(unsigned numberOfChannels, size_t length, bool allocate);
 
-    void speakersCopyFrom(const AudioBus&);
-    void discreteCopyFrom(const AudioBus&);
-    void speakersSumFrom(const AudioBus&);
     void discreteSumFrom(const AudioBus&);
-    void speakersSumFrom5_1_ToMono(const AudioBus&);
+
+    // Up/down-mix by in-place summing upon the existing channel content.
+    // http://webaudio.github.io/web-audio-api/#channel-up-mixing-and-down-mixing
+    void sumFromByUpMixing(const AudioBus&);
+    void sumFromByDownMixing(const AudioBus&);
 
     size_t m_length;
     Vector<OwnPtr<AudioChannel>> m_channels;