Add generic interfaces for the sinks of the media stream audio track

content/renderer/media/media_stream_audio_sink_owner.h

+// Copyright 2013 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_MEDIA_STREAM_AUDIO_SINK_OWNER_H_
+#define CONTENT_RENDERER_MEDIA_MEDIA_STREAM_AUDIO_SINK_OWNER_H_
+
+#include <vector>
+
+#include "base/memory/ref_counted.h"
+#include "base/synchronization/lock.h"
+#include "content/public/renderer/media_stream_audio_sink.h"
+#include "content/renderer/media/webrtc_audio_device_impl.h"
+#include "media/audio/audio_parameters.h"
+
+namespace content {
+
+// Reference counted container of MediaStreamAudioSink delegates.

[Jói, 2013/11/27 17:35:02]

It might be worth mentioning that this is a temporary type while we still have
two different types of sinks?

Also, "container of MediaStreamAudioSink delegates" seems inaccurate since this
is for either that type or for PeerConnectionAudioSink. Perhaps "holder of audio
stream sinks"?

[no longer working on chromium, 2013/11/28 17:27:18]

Added a TODO to remind removing the PeerConnectionAudioSink code.
Done.

+class MediaStreamAudioSinkOwner
+    : public base::RefCountedThreadSafe<MediaStreamAudioSinkOwner> {
+ public:
+  explicit MediaStreamAudioSinkOwner(MediaStreamAudioSink* sink);
+  explicit MediaStreamAudioSinkOwner(PeerConnectionAudioSink* sink);
+
+  // MediaStreamAudioSink implementation.
+  int OnData(const int16* audio_data,
+             int sample_rate,
+             int number_of_channels,
+             int number_of_frames,
+             const std::vector<int>& channels,
+             int audio_delay_milliseconds,
+             int current_volume,
+             bool need_audio_processing,
+             bool key_pressed);
+
+  void OnSetFormat(const media::AudioParameters& params);
+
+  bool IsEqual(const MediaStreamAudioSink* other) const;
+  bool IsEqual(const PeerConnectionAudioSink* other) const;
+  void Reset();
+
+  // Wrapper which allows to use std::find_if() when adding and removing

[Jói, 2013/11/27 17:35:02]

Would these wrappers be needed if we simply had two overloads of operator()
directly on MediaStreamAudioSinkOwner?

[no longer working on chromium, 2013/11/28 17:27:18]

It is a very interesting idea.
I guess you mean adding 
bool operator()(const scoped_refptr<MediaStreamAudioSinkOwner>& owner) {
  if (media_stream_delegate_)
    return owner->IsEqual(media_stream_delegate_);
  if (peer_connection_delegate_)
    return owner->IsEqual(peer_connection_delegate_);
}

The only problem for that is that MediaStreamAudioSinkOwner is reference
counted, so it won't work.

+  // sinks to/from the list.
+  struct WrapsSink {
+    WrapsSink(MediaStreamAudioSink* sink) : sink_(sink) {}
+    bool operator()(
+        const scoped_refptr<MediaStreamAudioSinkOwner>& owner) {
+      return owner->IsEqual(sink_);
+    }
+    MediaStreamAudioSink* sink_;
+  };
+
+  struct WrapsPeerConnectionSink {
+    WrapsPeerConnectionSink(PeerConnectionAudioSink* sink) : sink_(sink) {}
+    bool operator()(
+        const scoped_refptr<MediaStreamAudioSinkOwner>& owner) {
+      return owner->IsEqual(sink_);
+    }
+    PeerConnectionAudioSink* sink_;
+  };
+
+ protected:
+  virtual ~MediaStreamAudioSinkOwner() {}
+
+ private:
+  friend class base::RefCountedThreadSafe<MediaStreamAudioSinkOwner>;
+  MediaStreamAudioSink* media_stream_delegate_;

[tommi (sloooow) - chröme, 2013/11/28 09:12:11]

document ownership and how it's guaranteed that these pointers will never be
dangling.

[no longer working on chromium, 2013/11/28 17:27:18]

Done.

+  PeerConnectionAudioSink* peer_connection_delegate_;

[tommi (sloooow) - chröme, 2013/11/28 09:12:11]

why do we have these two mutually exclusive pointers in the same class?

[no longer working on chromium, 2013/11/28 17:27:18]

Done with separate the media stream sink owner and peer connection sink owner

+  mutable base::Lock lock_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaStreamAudioSinkOwner);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_MEDIA_MEDIA_STREAM_AUDIO_SINK_OWNER_H_