WebRtcMediaStreamTrackAdapter, maps 1 webrtc and 1 blink track

content/renderer/media/webrtc/webrtc_media_stream_track_adapter.h

+// Copyright (c) 2017 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.
+
+#ifndef CONTENT_RENDERER_MEDIA_WEBRTC_WEBRTC_MEDIA_STREAM_TRACK_ADAPTER_H_
+#define CONTENT_RENDERER_MEDIA_WEBRTC_WEBRTC_MEDIA_STREAM_TRACK_ADAPTER_H_
+
+#include <memory>
+
+#include "base/memory/ref_counted.h"
+#include "content/common/content_export.h"
+#include "content/renderer/media/remote_media_stream_track_adapter.h"
+#include "content/renderer/media/webrtc/media_stream_video_webrtc_sink.h"
+#include "content/renderer/media/webrtc/webrtc_audio_sink.h"
+#include "content/renderer/media/webrtc/webrtc_media_stream_track_adapter.h"
+#include "third_party/WebKit/public/platform/WebMediaStream.h"
+#include "third_party/WebKit/public/platform/WebMediaStreamTrack.h"
+#include "third_party/webrtc/api/mediastreaminterface.h"
+
+namespace content {
+
+class PeerConnectionDependencyFactory;
+
+// This is a mapping between a webrtc and blink media stream track. It takes
+// care of creation, initialization and uninitialization independently of media
+// streams.
+// There are different sinks/adapters used whether the track is local or remote
+// and whether it is an audio or video track; this adapter hides that fact and
+// lets you use a single class for any type of track.
+class CONTENT_EXPORT WebRtcMediaStreamTrackAdapter
+    : public base::RefCountedThreadSafe<WebRtcMediaStreamTrackAdapter> {
+ public:
+  // Invoke on the main thread. Construction and initialization happens here,
+  // ensuring |is_initialized| is true for the returned adapter.
+  static scoped_refptr<WebRtcMediaStreamTrackAdapter> CreateLocalTrackAdapter(
+      PeerConnectionDependencyFactory* factory,
+      const scoped_refptr<base::SingleThreadTaskRunner>& main_thread,
+      const blink::WebMediaStreamTrack& web_track);
+  // Invoke on the webrtc signaling thread. Initialization completes on the main
+  // thread in a post. |is_initialized| is ensured in posts to the main thread

[Guido Urdaneta, 2017/05/22 14:26:38]

Please update this comment.
What is |is_initialized| and what does it mean that it is ensured and why is
that important to document here?

[hbos_chromium, 2017/05/29 11:24:17]

Done.

+  // subsequent to |CreateRemoteTrackAdapter|.
+  static scoped_refptr<WebRtcMediaStreamTrackAdapter> CreateRemoteTrackAdapter(
+      PeerConnectionDependencyFactory* factory,
+      const scoped_refptr<base::SingleThreadTaskRunner>& main_thread,
+      webrtc::MediaStreamTrackInterface* webrtc_track);
+  // Invoke on the main thread. Uninitialization may finish asynchronously using
+  // the webrtc signaling thread and the main thread. After calling this method
+  // it is safe to release all external references to the adapter.
+  // Must be invoked after initialization is finished and before destruction.
+  void Uninitialize();

[Guido Urdaneta, 2017/05/22 14:26:38]

Does the term Uninitialize come from existing code?
If not, perhaps it would be better to rename it to something else. Close(),
Dispose()?

[hbos_chromium, 2017/05/29 11:24:17]

Done.

+
+  bool is_initialized() const;
+  const blink::WebMediaStreamTrack& web_track() const;
+  webrtc::MediaStreamTrackInterface* webrtc_track() const;
+  bool IsEqual(const blink::WebMediaStreamTrack& web_track) const;
+
+  // For testing.
+  WebRtcAudioSink* GetLocalAudioSinkForTesting() {
+    return local_audio_sink_.get();
+  }
+  MediaStreamVideoWebRtcSink* GetLocalVideoSinkForTesting() {
+    return local_video_sink_.get();
+  }
+  RemoteAudioTrackAdapter* GetRemoteAudioTrackAdapterForTesting() {
+    return remote_audio_track_adapter_.get();
+  }
+  RemoteVideoTrackAdapter* GetRemoteVideoTrackAdapterForTesting() {
+    return remote_video_track_adapter_.get();
+  }
+
+ protected:
+  friend class base::RefCountedThreadSafe<WebRtcMediaStreamTrackAdapter>;
+
+  WebRtcMediaStreamTrackAdapter(
+      PeerConnectionDependencyFactory* factory,
+      const scoped_refptr<base::SingleThreadTaskRunner>& main_thread);
+  virtual ~WebRtcMediaStreamTrackAdapter();
+
+ private:
+  // Initialization of local tracks occurs on the main thread.
+  void InitializeLocalAudioTrack(const blink::WebMediaStreamTrack& web_track);
+  void InitializeLocalVideoTrack(const blink::WebMediaStreamTrack& web_track);
+  // Initialization of remote tracks starts on the webrtc signaling thread and
+  // finishes on the main thread.
+  void InitializeRemoteAudioTrack(
+      webrtc::AudioTrackInterface* webrtc_audio_track);
+  void InitializeRemoteVideoTrack(
+      webrtc::VideoTrackInterface* webrtc_video_track);
+  void FinalizeRemoteTrackInitializationOnMainThread();
+
+  // Uninitialization of local tracks occurs on the main thread.
+  void UninitializeLocalAudioTrack();
+  void UninitializeLocalVideoTrack();
+  // Uninitialization of remote tracks starts on the main thread and finishes on
+  // the webrtc signaling thread.

[hbos_chromium, 2017/05/18 11:46:04]

Oops, need to update this comment, it starts and finishes on the main thread in
both cases. In the audio case it jumps to the signaling thread and back, in the
video case it doesn't have to post at all.

[Guido Urdaneta, 2017/05/22 14:26:38]

Perhaps you should just remove the comment. The comment only had implementation
details anyway.

[hbos_chromium, 2017/05/29 11:24:17]

Comment updated. I'd like to document this even though it's private because
threading can easily become a mess.

[Guido Urdaneta, 2017/05/30 08:45:35]

Acknowledged.

+  void UninitializeRemoteAudioTrack();
+  void UninitializeRemoteVideoTrack();
+  void UnregisterRemoteAudioTrackAdapterOnSignalingThread();
+  void FinalizeRemoteTrackUninitalizationOnMainThread();
+
+  // Pointer to a |PeerConnectionDependencyFactory| owned by the |RenderThread|.
+  // It's valid for the lifetime of |RenderThread|.
+  PeerConnectionDependencyFactory* const factory_;
+  scoped_refptr<base::SingleThreadTaskRunner> main_thread_;
+
+  // This class is "const" between being initialized (triggered by |Create...|)
+  // and being uninitialized (by calling |Uninitialize|). As such, no locks are
+  // required in the implementation for only inherently racey actions could
+  // cause problems (such as uninitializing while still in use).
+  bool is_initialized_;
+  blink::WebMediaStreamTrack web_track_;
+  scoped_refptr<webrtc::MediaStreamTrackInterface> webrtc_track_;
+  // If |track_| is local, a sink is added to the local webrtc track that is
+  // owned by us.
+  std::unique_ptr<WebRtcAudioSink> local_audio_sink_;

[Guido Urdaneta, 2017/05/22 14:26:38]

It seems to me that what is local about this sink is that the track has a local
source. 
Maybe |local_track_audio_sink_| is clearer?

[hbos_chromium, 2017/05/29 11:24:17]

Done.

+  std::unique_ptr<MediaStreamVideoWebRtcSink> local_video_sink_;
+  // If |track_| is remote, an adapter is used that listens to notifications on
+  // the remote webrtc track and notifies WebKit.
+  scoped_refptr<RemoteAudioTrackAdapter> remote_audio_track_adapter_;
+  scoped_refptr<RemoteVideoTrackAdapter> remote_video_track_adapter_;
+
+  DISALLOW_COPY_AND_ASSIGN(WebRtcMediaStreamTrackAdapter);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_MEDIA_WEBRTC_WEBRTC_MEDIA_STREAM_TRACK_ADAPTER_H_