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

content/renderer/media/webrtc/webrtc_local_audio_track_adapter.h

Index: content/renderer/media/webrtc/webrtc_local_audio_track_adapter.h
diff --git a/content/renderer/media/webrtc/webrtc_local_audio_track_adapter.h b/content/renderer/media/webrtc/webrtc_local_audio_track_adapter.h
index 72b80194b08ed09a01673c98c4ed9816aa4e6d74..899e1abf5584ae6ad1bd6d4ce7b3cb976671a28f 100644
--- a/content/renderer/media/webrtc/webrtc_local_audio_track_adapter.h
+++ b/content/renderer/media/webrtc/webrtc_local_audio_track_adapter.h
@@ -8,7 +8,7 @@
 #include <vector>
 
 #include "base/memory/ref_counted.h"
-#include "base/memory/scoped_vector.h"
+#include "base/memory/weak_ptr.h"
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/lock.h"
 #include "content/common/content_export.h"
@@ -17,8 +17,8 @@
 #include "third_party/webrtc/api/mediastreamtrack.h"
 #include "third_party/webrtc/media/base/audiorenderer.h"
 
-namespace cricket {
-class AudioRenderer;
+namespace base {
+class WaitableEvent;
 }
 
 namespace webrtc {
@@ -29,8 +29,8 @@ class AudioProcessorInterface;
 namespace content {
 
 class MediaStreamAudioProcessor;
+class MediaStreamAudioTrack;
 class WebRtcAudioSinkAdapter;
-class WebRtcLocalAudioTrack;
 
 // Provides an implementation of the webrtc::AudioTrackInterface that can be
 // bound/unbound to/from a MediaStreamAudioTrack.  In other words, this is an
@@ -51,7 +51,10 @@ class CONTENT_EXPORT WebRtcLocalAudioTrackAdapter
 
   ~WebRtcLocalAudioTrackAdapter() override;
 
-  void Initialize(WebRtcLocalAudioTrack* owner);
+  // Set the |track| that manages the MediaStreamAudioSinks.  The WeakPtr will
+  // only be dereferenced on the main thread.  This method must only be called
+  // on the main thread.
+  void SetMediaStreamAudioTrack(base::WeakPtr<MediaStreamAudioTrack> track);
 
   // Set the object that provides shared access to the current audio signal
   // level.  This method may only be called once, before the audio data flow
@@ -79,23 +82,38 @@ class CONTENT_EXPORT WebRtcLocalAudioTrackAdapter
       override;
   webrtc::AudioSourceInterface* GetSource() const override;
 
-  // Weak reference.
-  WebRtcLocalAudioTrack* owner_;
+  // Removes the |sink| from |track_| and then signals the |done_event| (if
+  // provided).  This is used by RemoveSink() to ensure the audio flow has
+  // halted before it returns.
+  void RemoveSinkOnMainThread(webrtc::AudioTrackSinkInterface* sink,
+                              base::WaitableEvent* done_event);
 
   // The source of the audio track which handles the audio constraints.
-  // TODO(xians): merge |track_source_| to |capturer_| in WebRtcLocalAudioTrack.
-  rtc::scoped_refptr<webrtc::AudioSourceInterface> track_source_;
+  const rtc::scoped_refptr<webrtc::AudioSourceInterface> track_source_;
 
-  // Libjingle's signaling thread.
+  // Task runner for operations that must be done on libjingle's signaling
+  // thread.  May be null for single-threaded unit tests.
   const scoped_refptr<base::SingleThreadTaskRunner> signaling_task_runner_;
 
+  // Task runner for operations that must be done on the main thread.  May be
+  // null for single-threaded unit tests.
+  scoped_refptr<base::SingleThreadTaskRunner> main_task_runner_;
+
+  // The track to add/remove sinks to/from.  When the
+  // webrtc::AudioTrackInterface::Add/RemoveSink() methods are called, they
+  // create a proxy (WebRtcAudioSinkAdapter) that implements the
+  // MediaStreamAudioSink interface to call into the
+  // webrtc::AudioTrackSinkInterface.  This must only be dereferenced on the
+  // main thread.
+  base::WeakPtr<MediaStreamAudioTrack> track_;
+
   // The audio processsor that applies audio processing on the data of audio
   // track.  This must be set before calls to GetAudioProcessor() are made.
   scoped_refptr<MediaStreamAudioProcessor> audio_processor_;
 
   // A vector of the peer connection sink adapters which receive the audio data
   // from the audio track.
-  ScopedVector<WebRtcAudioSinkAdapter> sink_adapters_;
+  std::vector<scoped_ptr<WebRtcAudioSinkAdapter>> sink_adapters_;
 
   // Thread-safe accessor to current audio signal level.  This must be set
   // before calls to GetSignalLevel() are made.