Use base::Optional for selected video track.

media/blink/webmediaplayer_impl.cc

Index: media/blink/webmediaplayer_impl.cc
diff --git a/media/blink/webmediaplayer_impl.cc b/media/blink/webmediaplayer_impl.cc
index f8c8d24f13ce728929938606f35f67c547e7243d..9d24d641bc87dcadb55651edae82d2f86377436f 100644
--- a/media/blink/webmediaplayer_impl.cc
+++ b/media/blink/webmediaplayer_impl.cc
@@ -669,15 +669,13 @@ 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 {