Handle Alpha channel in Canvas capture

content/renderer/media/media_stream_video_track.cc

Index: content/renderer/media/media_stream_video_track.cc
diff --git a/content/renderer/media/media_stream_video_track.cc b/content/renderer/media/media_stream_video_track.cc
index 6ff4688ce3dac0dec9825c07574c7478d64d378f..e9cc8e0716252138f78acc9ee8a829d18baa8e35 100644
--- a/content/renderer/media/media_stream_video_track.cc
+++ b/content/renderer/media/media_stream_video_track.cc
@@ -175,9 +175,9 @@ MediaStreamVideoTrack::FrameDeliverer::GetBlackFrame(
   // Wrap |black_frame_| so we get a fresh timestamp we can modify. Frames
   // returned from this function may still be in use.
   scoped_refptr<media::VideoFrame> wrapped_black_frame =
-      media::VideoFrame::WrapVideoFrame(
-          black_frame_, black_frame_->visible_rect(),
-          black_frame_->natural_size());
+      media::VideoFrame::WrapVideoFrame(black_frame_, black_frame_->format(),
+                                        black_frame_->visible_rect(),
+                                        black_frame_->natural_size());
   if (!wrapped_black_frame)
     return nullptr;
   wrapped_black_frame->AddDestructionObserver(