Fix crash when pipeline is stopped while video restart is pending

Media renderer might get destroyed (due to pipeline being stopped or
suspended) while a video track restart is pending. When that happens
the VideoRendererImpl has a pending flush_cb_ that will get called from
video renderer destructor invoking RendererImpl::RestartVideoRenderer,
so RestartVideoRenderer needs to actually try restarting the video
renderer only if we are still in the playing state.

BUG=668963

Review-Url: https://codereview.chromium.org/2570773002
Cr-Commit-Position: refs/heads/master@{#441457}

media/renderers/renderer_impl.cc

@@ -111,6 +111,11 @@ RendererImpl::~RendererImpl() {
   DVLOG(1) << __func__;
   DCHECK(task_runner_->BelongsToCurrentThread());
 
+  // RendererImpl is being destroyed, so invalidate weak pointers right away to
+  // avoid getting callbacks which might try to access fields that has been
+  // destroyed, e.g. audio_renderer_/video_renderer_ below (crbug.com/668963).
+  weak_factory_.InvalidateWeakPtrs();
+
   // Tear down in opposite order of construction as |video_renderer_| can still
   // need |time_source_| (which can be |audio_renderer_|) to be alive.
   video_renderer_.reset();
@@ -652,8 +657,8 @@ void RendererImpl::OnBufferingStateChange(DemuxerStream::Type type,
         deferred_video_underflow_cb_.IsCancelled()) {
       DVLOG(4) << __func__ << " Deferring HAVE_NOTHING for video stream.";
       deferred_video_underflow_cb_.Reset(
-          base::Bind(&RendererImpl::OnBufferingStateChange,
-                     weak_factory_.GetWeakPtr(), type, new_buffering_state));
+          base::Bind(&RendererImpl::OnBufferingStateChange, weak_this_, type,
+                     new_buffering_state));
       task_runner_->PostDelayedTask(FROM_HERE,
                                     deferred_video_underflow_cb_.callback(),
                                     video_underflow_threshold_);

media/test/pipeline_integration_test.cc

@@ -1065,6 +1065,36 @@ TEST_F(PipelineIntegrationTest, TrackStatusChangesWhileSuspended) {
   ASSERT_TRUE(WaitUntilOnEnded());
 }
 
+TEST_F(PipelineIntegrationTest, PipelineStoppedWhileAudioRestartPending) {
+  ASSERT_EQ(PIPELINE_OK, Start("bear-320x240.webm"));
+  Play();
+
+  // Disable audio track first, to re-enable it later and stop the pipeline
+  // (which destroys the media renderer) while audio restart is pending.
+  std::vector<MediaTrack::Id> track_ids;
+  pipeline_->OnEnabledAudioTracksChanged(track_ids);
+  ASSERT_TRUE(WaitUntilCurrentTimeIsAfter(TimestampMs(200)));
+
+  track_ids.push_back("2");
+  pipeline_->OnEnabledAudioTracksChanged(track_ids);
+  Stop();
+}
+
+TEST_F(PipelineIntegrationTest, PipelineStoppedWhileVideoRestartPending) {
+  ASSERT_EQ(PIPELINE_OK, Start("bear-320x240.webm"));
+  Play();
+
+  // Disable video track first, to re-enable it later and stop the pipeline
+  // (which destroys the media renderer) while video restart is pending.
+  std::vector<MediaTrack::Id> track_ids;
+  pipeline_->OnSelectedVideoTrackChanged(track_ids);
+  ASSERT_TRUE(WaitUntilCurrentTimeIsAfter(TimestampMs(200)));
+
+  track_ids.push_back("1");
+  pipeline_->OnSelectedVideoTrackChanged(track_ids);
+  Stop();
+}
+
 TEST_F(PipelineIntegrationTest,
        MAYBE_CLOCKLESS(BasicPlaybackOpusOggTrimmingHashed)) {
   ASSERT_EQ(PIPELINE_OK,