[BreakoutBox] Use weak pointer in MediaStreamVideoTrackUnderlyingSink

Replace the raw pointer to a PushableMediaStreamVideoSource with
a weak pointer.

Bug: 1162036
Change-Id: I9b786cfd3800f8e37daabacf039e6b12e2423f76
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2610036
Auto-Submit: Guido Urdaneta <guidou@chromium.org>
Reviewed-by: Thomas Guilbert <tguilbert@chromium.org>
Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Reviewed-by: Harald Alvestrand <hta@chromium.org>
Commit-Queue: Guido Urdaneta <guidou@chromium.org>
Cr-Commit-Position: refs/heads/master@{#840551}

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

@@ -12,7 +12,7 @@ namespace blink {
 
 MediaStreamVideoTrackUnderlyingSink::MediaStreamVideoTrackUnderlyingSink(
     PushableMediaStreamVideoSource* source)
-    : source_(source) {}
+    : source_(source->GetWeakPtr()) {}
 
 ScriptPromise MediaStreamVideoTrackUnderlyingSink::start(
     ScriptState* script_state,
@@ -39,14 +39,16 @@ ScriptPromise MediaStreamVideoTrackUnderlyingSink::write(
     return ScriptPromise();
   }
 
-  if (!source_->running()) {
+  PushableMediaStreamVideoSource* pushable_source =
+      static_cast<PushableMediaStreamVideoSource*>(source_.get());
+  if (!pushable_source || !pushable_source->running()) {
     exception_state.ThrowDOMException(DOMExceptionCode::kInvalidStateError,
                                       "Stream closed");
     return ScriptPromise();
   }
 
   base::TimeTicks estimated_capture_time = base::TimeTicks::Now();
-  source_->PushFrame(video_frame->frame(), estimated_capture_time);
+  pushable_source->PushFrame(video_frame->frame(), estimated_capture_time);
   // Invalidate the JS |video_frame|. Otherwise, the media frames might not be
   // released, which would leak resources and also cause some MediaStream
   // sources such as cameras to drop frames.
@@ -59,14 +61,16 @@ ScriptPromise MediaStreamVideoTrackUnderlyingSink::abort(
     ScriptState* script_state,
     ScriptValue reason,
     ExceptionState& exception_state) {
-  source_->StopSource();
+  if (source_)
+    source_->StopSource();
   return ScriptPromise::CastUndefined(script_state);
 }
 
 ScriptPromise MediaStreamVideoTrackUnderlyingSink::close(
     ScriptState* script_state,
     ExceptionState& exception_state) {
-  source_->StopSource();
+  if (source_)
+    source_->StopSource();
   return ScriptPromise::CastUndefined(script_state);
 }
 

third_party/blink/renderer/modules/mediastream/media_stream_video_track_underlying_sink.h

@@ -10,6 +10,7 @@
 
 namespace blink {
 
+class MediaStreamVideoSource;
 class PushableMediaStreamVideoSource;
 
 class MODULES_EXPORT MediaStreamVideoTrackUnderlyingSink
@@ -34,7 +35,7 @@ class MODULES_EXPORT MediaStreamVideoTrackUnderlyingSink
                       ExceptionState& exception_state) override;
 
  private:
-  PushableMediaStreamVideoSource* source_;
+  base::WeakPtr<MediaStreamVideoSource> source_;
 };
 
 }  // namespace blink