Media is not resuming playback on window's focus/visibilitychange event

media/filters/pipeline_controller.cc

@@ -96,6 +96,12 @@ void PipelineController::Suspend() {
 void PipelineController::Resume() {
   DCHECK(thread_checker_.CalledOnValidThread());
   pending_suspend_ = false;
+
+  if (state_ == State::SWITCHING_TRACKS) {
+    defer_playback_resume_ = true;
+    return;
+  }
+
   if (state_ == State::SUSPENDING || state_ == State::SUSPENDED) {
     pending_resume_ = true;
     Dispatch();
@@ -437,7 +443,13 @@ void PipelineController::FireOnTrackChangeCompleteForTesting(State set_to) {
 void PipelineController::OnTrackChangeComplete(State previous_state) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
-  if (state_ == State::SWITCHING_TRACKS)
+  if (defer_playback_resume_) {
+    state_ = State::SUSPENDED;
+    defer_playback_resume_ = false;
+    Resume();
+    return;
+  }
+  else if (state_ == State::SWITCHING_TRACKS)
     state_ = previous_state;
 
   // Other track changed or seek/suspend/resume, etc may be waiting.

media/filters/pipeline_controller.h

@@ -220,6 +220,15 @@ class MEDIA_EXPORT PipelineController {
   std::vector<MediaTrack::Id> pending_audio_track_change_ids_;
   base::Optional<MediaTrack::Id> pending_video_track_change_id_;
 
+  // Defer playback resume basing on this flag.
+  // In some corner case when pausing a video on blur/visibilitychange
+  // event and then resuming a video on a tab focus/visibilitychange
+  // event there may be a race condition between
+  // changing video tracks (state: 5) and resuming playback (state: 8).
+  // Because of that the new "RESUMING" state is not assigned and a video
+  // is not starting when a tab with the video is again in focus.
+  bool defer_playback_resume_ = false;
+
   // Set to true during Start(). Indicates that |seeked_cb_| must be fired once
   // we've completed startup.
   bool pending_startup_ = false;

media/filters/pipeline_controller_unittest.cc

@@ -535,4 +535,17 @@ TEST_F(PipelineControllerTest, SuspendDuringAudioTrackChange) {
   EXPECT_FALSE(was_resumed_);
 }
 
+TEST_F(PipelineControllerTest, ResumePlaybackDuringSwitchingTracksState) {
+  Complete(StartPipeline());
+  Complete(SuspendPipeline());
+  EXPECT_CALL(*pipeline_, OnSelectedVideoTrackChanged(_, _)).Times(1);
+  EXPECT_CALL(*pipeline_, GetMediaTime()).Times(1);
+  EXPECT_CALL(*pipeline_, OnResume(_, _)).Times(1);
+
+  pipeline_controller_.OnSelectedVideoTrackChanged({});
+  pipeline_controller_.Resume();
+  pipeline_controller_.FireOnTrackChangeCompleteForTesting(
+      PipelineController::State::PLAYING);
+}
+
 }  // namespace media