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

content/renderer/media/media_stream_video_capturer_source.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/media/media_stream_video_capturer_source.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 637 matching lines @@
                  base::Unretained(this)));
 }
 
 void MediaStreamVideoCapturerSource::StopSourceImpl() {
   source_->StopCapture();
 }
 
 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) {
   if (is_capture_starting_) {
     OnStartDone(is_running ? MEDIA_DEVICE_OK
                            : MEDIA_DEVICE_TRACK_START_FAILURE);
     is_capture_starting_ = false;
   } else if (!is_running) {
     StopSource();
   }
 }
 
 const char*
 MediaStreamVideoCapturerSource::GetPowerLineFrequencyForTesting() const {
   return kPowerLineFrequency;
 }
 
 }  // namespace content