Allow media track switching.

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 813a643f7cf0fc1e93183549f5163e3738b9889f..fd9b26d8e1ce356c45a2b44803873e468a152a6e 100644
--- a/media/blink/webmediaplayer_impl.cc
+++ b/media/blink/webmediaplayer_impl.cc
@@ -1039,19 +1039,23 @@ void WebMediaPlayerImpl::OnFFmpegMediaTracksUpdated(
   DCHECK(!chunk_demuxer_);
 
   // Report the media track information to blink.
+  bool first_audio_track = true;
+  bool first_video_track = true;
   for (const auto& track : tracks->tracks()) {
     if (track->type() == MediaTrack::Audio) {
       client_->addAudioTrack(blink::WebString::fromUTF8(track->id()),
                              blink::WebMediaPlayerClient::AudioTrackKindMain,
                              blink::WebString::fromUTF8(track->label()),
                              blink::WebString::fromUTF8(track->language()),
-                             /*enabled*/ true);
+                             /*enabled*/ first_audio_track);
+      first_audio_track = false;
     } else if (track->type() == MediaTrack::Video) {
       client_->addVideoTrack(blink::WebString::fromUTF8(track->id()),
                              blink::WebMediaPlayerClient::VideoTrackKindMain,
                              blink::WebString::fromUTF8(track->label()),
                              blink::WebString::fromUTF8(track->language()),
-                             /*selected*/ true);
+                             /*selected*/ first_video_track);
+      first_video_track = false;
     } else {
       // Text tracks are not supported through this code path yet.
       NOTREACHED();