Use explicit conversion to base::Optional in MSVS::GetCurrentFormatImpl implementations.

content/renderer/media/media_stream_video_capturer_source.cc

Index: content/renderer/media/media_stream_video_capturer_source.cc
diff --git a/content/renderer/media/media_stream_video_capturer_source.cc b/content/renderer/media/media_stream_video_capturer_source.cc
index 62cf8d18310a883443bdfe0afe17178c080d4825..1eccdda77dd69796000090dc02d7bf316c3277d9 100644
--- a/content/renderer/media/media_stream_video_capturer_source.cc
+++ b/content/renderer/media/media_stream_video_capturer_source.cc
@@ -655,7 +655,8 @@ void MediaStreamVideoCapturerSource::StopSourceImpl() {
 base::Optional<media::VideoCaptureFormat>
 MediaStreamVideoCapturerSource::GetCurrentFormatImpl() const {
   DCHECK(!IsOldVideoConstraints());
-  return capture_params_.requested_format;
+  return base::Optional<media::VideoCaptureFormat>(
+      capture_params_.requested_format);
 }
 
 void MediaStreamVideoCapturerSource::OnRunStateChanged(bool is_running) {