Use base::Optional for selected video track.

media/blink/webmediaplayer_impl.cc

 // Copyright 2013 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 "media/blink/webmediaplayer_impl.h"
 
 #include <algorithm>
 #include <cmath>
 #include <limits>
 #include <string>
@@ skipping 651 matching lines @@
   }
   MEDIA_LOG(INFO, media_log_) << "Enabled audio tracks: [" << logstr.str()
                               << "]";
   pipeline_.OnEnabledAudioTracksChanged(enabledMediaTrackIds);
 }
 
 void WebMediaPlayerImpl::selectedVideoTrackChanged(
     blink::WebMediaPlayer::TrackId* selectedTrackId) {
   DCHECK(main_task_runner_->BelongsToCurrentThread());
 
-  std::ostringstream logstr;
-  std::vector<MediaTrack::Id> selectedVideoMediaTrackId;
-  if (selectedTrackId && !video_track_disabled_) {
-    selectedVideoMediaTrackId.push_back(selectedTrackId->utf8().data());
-    logstr << selectedVideoMediaTrackId[0];
-  }
-  MEDIA_LOG(INFO, media_log_) << "Selected video track: [" << logstr.str()
-                              << "]";
-  pipeline_.OnSelectedVideoTrackChanged(selectedVideoMediaTrackId);
+  base::Optional<MediaTrack::Id> selectedVideoTrackId;

[watk, 2017/02/23 20:57:54]

naming convention

[servolk, 2017/02/23 21:15:48]

Done.

+  if (selectedTrackId && !video_track_disabled_)
+    selectedVideoTrackId = MediaTrack::Id(selectedTrackId->utf8().data());
+  MEDIA_LOG(INFO, media_log_)
+      << "Selected video track: ["
+      << (selectedVideoTrackId ? *selectedVideoTrackId : "") << "]";

[watk, 2017/02/23 20:57:54]

Could use .value_or("") to make it slightly shorter.

[servolk, 2017/02/23 21:15:48]

Done.

+  pipeline_.OnSelectedVideoTrackChanged(selectedVideoTrackId);
 }
 
 blink::WebSize WebMediaPlayerImpl::naturalSize() const {
   DCHECK(main_task_runner_->BelongsToCurrentThread());
 
   return blink::WebSize(pipeline_metadata_.natural_size);
 }
 
 bool WebMediaPlayerImpl::paused() const {
   DCHECK(main_task_runner_->BelongsToCurrentThread());
@@ skipping 1604 matching lines @@
 
 void WebMediaPlayerImpl::RecordUnderflowDuration(base::TimeDelta duration) {
   DCHECK(data_source_ || chunk_demuxer_);
   if (data_source_)
     UMA_HISTOGRAM_TIMES("Media.UnderflowDuration", duration);
   else
     UMA_HISTOGRAM_TIMES("Media.UnderflowDuration.MSE", duration);
 }
 
 }  // namespace media