Implement disabling and enabling media tracks

media/filters/chunk_demuxer.cc

Index: media/filters/chunk_demuxer.cc
diff --git a/media/filters/chunk_demuxer.cc b/media/filters/chunk_demuxer.cc
index 49836a129e580d085c1ca956ac27d7c5ac3bea90..097085e81518d5b93060e4983c1465fbfa3e0393 100644
--- a/media/filters/chunk_demuxer.cc
+++ b/media/filters/chunk_demuxer.cc
@@ -38,7 +38,8 @@ ChunkDemuxerStream::ChunkDemuxerStream(Type type,
       media_track_id_(media_track_id),
       state_(UNINITIALIZED),
       splice_frames_enabled_(splice_frames_enabled),
-      partial_append_window_trimming_enabled_(false) {}
+      partial_append_window_trimming_enabled_(false),
+      is_enabled_(true) {}
 
 void ChunkDemuxerStream::StartReturningData() {
   DVLOG(1) << "ChunkDemuxerStream::StartReturningData()";
@@ -244,6 +245,14 @@ void ChunkDemuxerStream::Read(const ReadCB& read_cb) {
   DCHECK(read_cb_.is_null());
 
   read_cb_ = BindToCurrentLoop(read_cb);
+
+  if (!is_enabled_) {
+    DVLOG(1) << "Read from disabled stream, returning EOS";
+    base::ResetAndReturn(&read_cb_).Run(kOk,
+                                        StreamParserBuffer::CreateEOSBuffer());
+    return;
+  }
+
   CompletePendingReadIfPossible_Locked();
 }
 
@@ -272,6 +281,35 @@ VideoRotation ChunkDemuxerStream::video_rotation() {
   return VIDEO_ROTATION_0;
 }
 
+bool ChunkDemuxerStream::enabled() const {
+  base::AutoLock auto_lock(lock_);
+  return is_enabled_;
+}
+
+void ChunkDemuxerStream::set_enabled(bool enabled, base::TimeDelta timestamp) {
+  base::AutoLock auto_lock(lock_);
+
+  if (enabled == is_enabled_)
+    return;
+
+  is_enabled_ = enabled;
+  if (enabled) {
+    DCHECK(stream_);
+    stream_->Seek(timestamp);
+    if (!stream_restarted_cb_.is_null())
+      stream_restarted_cb_.Run(this, timestamp);
+  } else if (!read_cb_.is_null()) {
+    DVLOG(1) << "Read from disabled stream, returning EOS";
+    base::ResetAndReturn(&read_cb_).Run(kOk,
+                                        StreamParserBuffer::CreateEOSBuffer());
+  }
+}
+
+void ChunkDemuxerStream::SetStreamRestartedCB(const StreamRestartedCB& cb) {
+  DCHECK(!cb.is_null());
+  stream_restarted_cb_ = cb;
+}
+
 TextTrackConfig ChunkDemuxerStream::text_track_config() {
   CHECK_EQ(type_, TEXT);
   base::AutoLock auto_lock(lock_);
@@ -593,6 +631,38 @@ Ranges<TimeDelta> ChunkDemuxer::GetBufferedRanges(const std::string& id) const {
   return itr->second->GetBufferedRanges(duration_, state_ == ENDED);
 }
 
+void ChunkDemuxer::OnEnabledAudioTracksChanged(
+    const std::vector<MediaTrack::Id>& track_ids,
+    base::TimeDelta currTime) {
+  // Note: We intentionally don't lock here, since we are not accessing any

[chcunningham, 2016/06/24 23:32:55]

You are locking though ;)

[servolk, 2016/06/25 00:36:33]

But only while accessing |track_id_to_demux_stream_map_|. I agree we can do that
only when DCHECK_IS_ON.

+  // members directly.
+  DemuxerStream* audio_stream = GetStream(DemuxerStream::AUDIO);
+  bool enabled = false;
+  CHECK(audio_stream);
+  if (track_ids.size() > 0) {

[chcunningham, 2016/06/24 23:32:55]

IIUC size should never exceed 1 as currently implemented. DCHECK?

[servolk, 2016/06/25 00:36:33]

Done.

+    base::AutoLock auto_lock(lock_);

[chcunningham, 2016/06/24 23:32:55]

Seems you're not settled on this part. I wonder if you could put the lock and
the dcheck inside an ifdef for when DCHECKING is enabled. I forget the specific
define... something like DCHECK_ON 

[servolk, 2016/06/25 00:36:33]

Done.

+    // DCHECK(track_id_to_demux_stream_map_[track_ids[0]] == audio_stream);
+    enabled = true;
+  }
+  audio_stream->set_enabled(enabled, currTime);
+}
+
+void ChunkDemuxer::OnSelectedVideoTrackChanged(
+    const std::vector<MediaTrack::Id>& track_ids,
+    base::TimeDelta currTime) {
+  // Note: We intentionally don't lock here, since we are not accessing any

[chcunningham, 2016/06/24 23:32:55]

This method has the same unsettled state around the locking. Maybe take the same
approach here as I suggest above?

[servolk, 2016/06/25 00:36:33]

Done.

+  // members directly.
+  DemuxerStream* video_stream = GetStream(DemuxerStream::VIDEO);
+  bool enabled = false;
+  CHECK(video_stream);
+  if (track_ids.size() > 0) {
+    base::AutoLock auto_lock(lock_);
+    // DCHECK(track_id_to_demux_stream_map_[track_ids[0]] == video_stream);
+    enabled = true;
+  }
+  video_stream->set_enabled(enabled, currTime);
+}
+
 bool ChunkDemuxer::EvictCodedFrames(const std::string& id,
                                     base::TimeDelta currentMediaTime,
                                     size_t newDataSize) {