Use base::Optional for selected video track.

media/base/media_url_demuxer.cc

Index: media/base/media_url_demuxer.cc
diff --git a/media/base/media_url_demuxer.cc b/media/base/media_url_demuxer.cc
index 482df223797a90fc62d3380adb676a65d1567507..190ff2440fc7017c15a65314f6e03e0c7f2d39f7 100644
--- a/media/base/media_url_demuxer.cc
+++ b/media/base/media_url_demuxer.cc
@@ -75,12 +75,12 @@ int64_t MediaUrlDemuxer::GetMemoryUsage() const {
 
 void MediaUrlDemuxer::OnEnabledAudioTracksChanged(
     const std::vector<MediaTrack::Id>& track_ids,
-    base::TimeDelta currTime) {
+    base::TimeDelta curr_time) {
   NOTIMPLEMENTED();
 }
 void MediaUrlDemuxer::OnSelectedVideoTrackChanged(
-    const std::vector<MediaTrack::Id>& track_ids,
-    base::TimeDelta currTime) {
+    base::Optional<MediaTrack::Id> selected_track_id,
+    base::TimeDelta curr_time) {
   NOTIMPLEMENTED();
 }