Implement disabling and enabling media tracks

media/base/pipeline_impl.cc

Index: media/base/pipeline_impl.cc
diff --git a/media/base/pipeline_impl.cc b/media/base/pipeline_impl.cc
index 36747bd48b3cd7ba73421aa5d2de35966c903170..c7ee5b0965a52dfa09d2c818c95424edca03412f 100644
--- a/media/base/pipeline_impl.cc
+++ b/media/base/pipeline_impl.cc
@@ -57,6 +57,15 @@ class PipelineImpl::RendererWrapper : public DemuxerHost,
   PipelineStatistics GetStatistics() const;
   void SetCdm(CdmContext* cdm_context, const CdmAttachedCB& cdm_attached_cb);
 
+  // |enabledTrackIds| contains track ids of enabled audio tracks.
+  void OnEnabledAudioTracksChanged(
+      const std::vector<MediaTrack::Id>& enabledTrackIds);
+
+  // |trackId| either empty, which means no video track is selected, or contain
+  // one element - the selected video track id.
+  void OnSelectedVideoTrackChanged(
+      const std::vector<MediaTrack::Id>& selectedTrackId);
+
  private:
   // Contains state shared between main and media thread.
   // Main thread can only read. Media thread can both - read and write.
@@ -224,6 +233,24 @@ void PipelineImpl::Start(Demuxer* demuxer,
                  weak_factory_.GetWeakPtr()));
 }
 
+void PipelineImpl::OnEnabledAudioTracksChanged(
+    const std::vector<MediaTrack::Id>& enabledTrackIds) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  media_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&RendererWrapper::OnEnabledAudioTracksChanged,
+                 base::Unretained(renderer_wrapper_.get()), enabledTrackIds));
+}
+
+void PipelineImpl::OnSelectedVideoTrackChanged(
+    const std::vector<MediaTrack::Id>& selectedTrackId) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  media_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&RendererWrapper::OnSelectedVideoTrackChanged,
+                 base::Unretained(renderer_wrapper_.get()), selectedTrackId));
+}
+
 void PipelineImpl::Stop() {
   DVLOG(2) << __FUNCTION__;
   DCHECK(thread_checker_.CalledOnValidThread());
@@ -519,6 +546,40 @@ void PipelineImpl::RendererWrapper::OnEnded() {
   RunEndedCallbackIfNeeded();
 }
 
+void PipelineImpl::RendererWrapper::OnEnabledAudioTracksChanged(
+    const std::vector<MediaTrack::Id>& enabledTrackIds) {
+  DCHECK(media_task_runner_->BelongsToCurrentThread());
+
+  // This might happen at the very beginning of the media playback, when the
+  // first video track gets selected by default before the playback has been
+  // started, so we don't need to react to this.
+  if (!demuxer_ || !shared_state_.renderer) {
+    return;
+  }
+
+  base::TimeDelta currTime = (state_ == kPlaying)
+                                 ? shared_state_.renderer->GetMediaTime()
+                                 : start_timestamp_;
+  demuxer_->OnEnabledAudioTracksChanged(enabledTrackIds, currTime);
+}
+
+void PipelineImpl::RendererWrapper::OnSelectedVideoTrackChanged(
+    const std::vector<MediaTrack::Id>& selectedTrackId) {
+  DCHECK(media_task_runner_->BelongsToCurrentThread());
+
+  // This might happen at the very beginning of the media playback, when the
+  // first video track gets selected by default before the playback has been

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

What if something other than the first/default track is selected prior to
starting playback? Should we save the selection and apply once the demuxer comes
available? 

I'm not sure this is possible, but from a quick glance it seems it may sometimes
take a moment for the async initializition of the data_source in WMPI to
complete, meaning we may have a window of opportunity for non-default tracks to
be enabled.

+  // started, so we don't need to react to this.
+  if (!demuxer_ || !shared_state_.renderer) {
+    return;
+  }
+
+  base::TimeDelta currTime = (state_ == kPlaying)
+                                 ? shared_state_.renderer->GetMediaTime()
+                                 : start_timestamp_;
+  demuxer_->OnSelectedVideoTrackChanged(selectedTrackId, currTime);
+}
+
 void PipelineImpl::RendererWrapper::OnStatisticsUpdate(
     const PipelineStatistics& stats) {
   DVLOG(3) << __FUNCTION__;