Fix crash in blink::MediaStreamRemoteVideoSource::RequestRefreshFrame.

This change fixes a crash in RequestRefreshFrame and also a few other
potential cases found during code inspection.

Bug: 1040626
Change-Id: I1cdeaa76b530b833dbdad8ab239ae66ee08bac60
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1994287Reviewed-by: Henrik Boström <hbos@chromium.org>
Commit-Queue: Markus Handell <handellm@google.com>
Cr-Commit-Position: refs/heads/master@{#730137}

third_party/blink/renderer/modules/mediastream/media_stream_video_source.cc

@@ -335,7 +335,6 @@ size_t MediaStreamVideoSource::CountEncodedSinks() const {
 void MediaStreamVideoSource::UpdateNumEncodedSinks() {
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
   size_t count = CountEncodedSinks();
-  DCHECK(SupportsEncodedOutput() || count == 0);
   if (count == 1) {
     OnEncodedSinkEnabled();
   } else if (count == 0) {

third_party/blink/renderer/modules/peerconnection/media_stream_remote_video_source.cc

@@ -407,6 +407,9 @@ void MediaStreamRemoteVideoSource::OnChanged(
 
 bool MediaStreamRemoteVideoSource::SupportsEncodedOutput() const {
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
+  if (!observer_ || !observer_->track()) {
+    return false;
+  }
   scoped_refptr<webrtc::VideoTrackInterface> video_track(
       static_cast<webrtc::VideoTrackInterface*>(observer_->track().get()));
   return video_track->GetSource()->SupportsEncodedOutput();
@@ -414,6 +417,9 @@ bool MediaStreamRemoteVideoSource::SupportsEncodedOutput() const {
 
 void MediaStreamRemoteVideoSource::RequestRefreshFrame() {
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
+  if (!observer_ || !observer_->track()) {
+    return;
+  }
   scoped_refptr<webrtc::VideoTrackInterface> video_track(
       static_cast<webrtc::VideoTrackInterface*>(observer_->track().get()));
   if (video_track->GetSource()) {
@@ -423,6 +429,9 @@ void MediaStreamRemoteVideoSource::RequestRefreshFrame() {
 
 void MediaStreamRemoteVideoSource::OnEncodedSinkEnabled() {
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
+  if (!observer_ || !observer_->track()) {
+    return;
+  }
   scoped_refptr<webrtc::VideoTrackInterface> video_track(
       static_cast<webrtc::VideoTrackInterface*>(observer_->track().get()));
   video_track->GetSource()->AddEncodedSink(delegate_.get());
@@ -430,7 +439,7 @@ void MediaStreamRemoteVideoSource::OnEncodedSinkEnabled() {
 
 void MediaStreamRemoteVideoSource::OnEncodedSinkDisabled() {
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
-  if (!observer_->track()) {
+  if (!observer_ || !observer_->track()) {
     return;
   }
   scoped_refptr<webrtc::VideoTrackInterface> video_track(

third_party/blink/renderer/modules/peerconnection/media_stream_remote_video_source_test.cc

@@ -188,7 +188,31 @@ TEST_F(MediaStreamRemoteVideoSourceTest, StartTrack) {
   track->RemoveSink(&sink);
 }
 
-TEST_F(MediaStreamRemoteVideoSourceTest, RemoteTrackStop) {
+TEST_F(MediaStreamRemoteVideoSourceTest,
+       SourceTerminationWithEncodedSinkAdded) {
+  std::unique_ptr<blink::MediaStreamVideoTrack> track(CreateTrack());
+  blink::MockMediaStreamVideoSink sink;
+  track->AddEncodedSink(&sink, sink.GetDeliverEncodedVideoFrameCB());
+  source()->OnSourceTerminated();
+  track->RemoveEncodedSink(&sink);
+}
+
+TEST_F(MediaStreamRemoteVideoSourceTest,
+       SourceTerminationBeforeEncodedSinkAdded) {
+  std::unique_ptr<blink::MediaStreamVideoTrack> track(CreateTrack());
+  blink::MockMediaStreamVideoSink sink;
+  source()->OnSourceTerminated();
+  track->AddEncodedSink(&sink, sink.GetDeliverEncodedVideoFrameCB());
+  track->RemoveEncodedSink(&sink);
+}
+
+TEST_F(MediaStreamRemoteVideoSourceTest,
+       SourceTerminationBeforeRequestRefreshFrame) {
+  source()->OnSourceTerminated();
+  source()->RequestRefreshFrame();
+}
+
+TEST_F(MediaStreamRemoteVideoSourceTest, SurvivesSourceTermination) {
   std::unique_ptr<blink::MediaStreamVideoTrack> track(CreateTrack());
 
   blink::MockMediaStreamVideoSink sink;