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 119810f9214b8611ebb33a8a391d5fc556132f9b..4428384e4613bc2f841330df1bce7c37c9802c40 100644
--- a/media/blink/webmediaplayer_impl.cc
+++ b/media/blink/webmediaplayer_impl.cc
@@ -1040,19 +1040,23 @@ void WebMediaPlayerImpl::OnFFmpegMediaTracksUpdated(
   DCHECK(!chunk_demuxer_);
 
   // Report the media track information to blink.
+  bool is_first_audio_track = true;
+  bool is_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= */ is_first_audio_track);
+      is_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= */ is_first_video_track);
+      is_first_video_track = false;
     } else {
       // Text tracks are not supported through this code path yet.
       NOTREACHED();