Introduce PushPullFIFO class and remove other FIFOs

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

Index: third_party/WebKit/Source/platform/audio/AudioDestination.h
diff --git a/third_party/WebKit/Source/platform/audio/AudioDestination.h b/third_party/WebKit/Source/platform/audio/AudioDestination.h
index d0e35b80c7802e71e809db860a1a609cd40741cc..f5c699a181ffdbc4b13544953f8a64d9e501055e 100644
--- a/third_party/WebKit/Source/platform/audio/AudioDestination.h
+++ b/third_party/WebKit/Source/platform/audio/AudioDestination.h
@@ -31,7 +31,6 @@
 
 #include "platform/audio/AudioBus.h"
 #include "platform/audio/AudioIOCallback.h"
-#include "platform/audio/AudioSourceProvider.h"
 #include "public/platform/WebAudioDevice.h"
 #include "public/platform/WebVector.h"
 #include "wtf/Allocator.h"
@@ -41,15 +40,14 @@
 
 namespace blink {
 
-class AudioPullFIFO;
+class PushPullFIFO;
 class SecurityOrigin;
 
 // The AudioDestination class is an audio sink interface between the media
 // renderer and the Blink's WebAudio module. It has a FIFO to adapt the
 // different processing block sizes of WebAudio renderer and actual hardware
 // audio callback.
-class PLATFORM_EXPORT AudioDestination : public WebAudioDevice::RenderCallback,
-                                         public AudioSourceProvider {
+class PLATFORM_EXPORT AudioDestination : public WebAudioDevice::RenderCallback {
   USING_FAST_MALLOC(AudioDestination);
   WTF_MAKE_NONCOPYABLE(AudioDestination);
 
@@ -74,9 +72,6 @@ class PLATFORM_EXPORT AudioDestination : public WebAudioDevice::RenderCallback,
               double delayTimestamp,
               size_t priorFramesSkipped) override;
 
-  // AudioSourceProvider (FIFO)
-  void provideInput(AudioBus* outputBus, size_t framesToProcess) override;
-
   virtual void start();
   virtual void stop();
 
@@ -98,8 +93,15 @@ class PLATFORM_EXPORT AudioDestination : public WebAudioDevice::RenderCallback,
   // The render callback function of WebAudio engine. (i.e. DestinationNode)
   AudioIOCallback& m_callback;
 
+  // To pass the data from FIFO to the audio device callback.
   RefPtr<AudioBus> m_outputBus;
-  std::unique_ptr<AudioPullFIFO> m_fifo;
+
+  // To push the rendered result from WebAudio graph into the FIFO.

[Raymond Toy, 2017/01/09 22:46:02]

I'm sorry. "To pass" and "To push" don't really help me understand what
m_outputBus and m_renderBus hold.

[hongchan, 2017/01/10 21:15:58]

They are pointers. WebAudio renderer fill up the m_renderBus to push the data
into FIFO while the audio device callback uses m_outputBus to pull out the data
out of FIFO.

+  RefPtr<AudioBus> m_renderBus;
+
+  // Resolves the buffer size mismatch between the WebAudio engine and
+  // the callback function from the actual audio device.
+  std::unique_ptr<PushPullFIFO> m_fifo;
 
   size_t m_framesElapsed;
   AudioIOPosition m_outputPosition;