MediaStream audio: Refactor 3 separate "glue" implementations into one.

content/renderer/media/webrtc/webrtc_audio_sink_adapter.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "base/bind.h"
+#include "base/bind_helpers.h"
 #include "base/logging.h"
 #include "content/renderer/media/webrtc/webrtc_audio_sink_adapter.h"
 #include "media/base/audio_bus.h"
 #include "third_party/webrtc/api/mediastreaminterface.h"
 
 namespace content {
 
 WebRtcAudioSinkAdapter::WebRtcAudioSinkAdapter(
     webrtc::AudioTrackSinkInterface* sink)
-    : sink_(sink) {
+    : sink_(sink),
+      fifo_(base::Bind(&WebRtcAudioSinkAdapter::DeliverRebufferedAudio,
+                       base::Unretained(this))) {
   DCHECK(sink);
 }
 
 WebRtcAudioSinkAdapter::~WebRtcAudioSinkAdapter() {
 }
 
 bool WebRtcAudioSinkAdapter::IsEqual(
     const webrtc::AudioTrackSinkInterface* other) const {
   return (other == sink_);
 }
 
 void WebRtcAudioSinkAdapter::OnData(const media::AudioBus& audio_bus,
                                     base::TimeTicks estimated_capture_time) {
-  DCHECK_EQ(audio_bus.frames(), params_.frames_per_buffer());
-  DCHECK_EQ(audio_bus.channels(), params_.channels());
+  // The following will result in zero, one, or multiple synchronous calls to
+  // DeliverRebufferedAudio().
+  fifo_.Push(audio_bus);
+}
+
+void WebRtcAudioSinkAdapter::DeliverRebufferedAudio(
+    const media::AudioBus& audio_bus,
+    int frame_delay) {
+  // TODO(miu): Why doesn't a WebRTC sink care about reference time passed to
+  // OnData(), and the |frame_delay| here?  How is AV sync achieved otherwise?
+
   // TODO(henrika): Remove this conversion once the interface in libjingle
   // supports float vectors.
   audio_bus.ToInterleaved(audio_bus.frames(),
                           sizeof(interleaved_data_[0]),
                           interleaved_data_.get());
   sink_->OnData(interleaved_data_.get(),
                 16,
                 params_.sample_rate(),
                 audio_bus.channels(),
                 audio_bus.frames());
 }
 
 void WebRtcAudioSinkAdapter::OnSetFormat(
     const media::AudioParameters& params) {
   DCHECK(params.IsValid());
   params_ = params;
+  fifo_.Reset(params_.frames_per_buffer());

[o1ka, 2016/04/01 15:11:41]

What is the guarantee that there is no race between OnSetFormat() and OnData()?
It would be nice to have a comment or thread check

[miu, 2016/04/19 00:40:23]

Done.  (This method moved to the new WebRtcAudioSink class in Patch Set 4.)

   const int num_pcm16_data_elements =
       params_.frames_per_buffer() * params_.channels();
   interleaved_data_.reset(new int16_t[num_pcm16_data_elements]);
 }
 
 }  // namespace content