MediaStream Recorder: Support VP9 encoder

media/capture/webm_muxer.cc

Index: media/capture/webm_muxer.cc
diff --git a/media/capture/webm_muxer.cc b/media/capture/webm_muxer.cc
index c59bbae805293bc02d0463dc9fb37c5f1960756b..8c841e2fed8ecfc5de6f4a979ab572e140121d5f 100644
--- a/media/capture/webm_muxer.cc
+++ b/media/capture/webm_muxer.cc
@@ -25,8 +25,9 @@ static double GetFrameRate(const scoped_refptr<VideoFrame>& video_frame) {
   return frame_rate;
 }
 
-WebmMuxer::WebmMuxer(const WriteDataCB& write_data_callback)
-    : track_index_(0),
+WebmMuxer::WebmMuxer(bool use_vp9, const WriteDataCB& write_data_callback)
+    : use_vp9_(use_vp9),
+      track_index_(0),
       write_data_callback_(write_data_callback),
       position_(0) {
   DCHECK(!write_data_callback_.is_null());
@@ -82,7 +83,8 @@ void WebmMuxer::AddVideoTrack(const gfx::Size& frame_size, double frame_rate) {
       reinterpret_cast<mkvmuxer::VideoTrack*>(
           segment_.GetTrackByNumber(track_index_));
   DCHECK(video_track);
-  video_track->set_codec_id(mkvmuxer::Tracks::kVp8CodecId);
+  video_track->set_codec_id(use_vp9_ ? mkvmuxer::Tracks::kVp9CodecId
+                                     : mkvmuxer::Tracks::kVp8CodecId);
   DCHECK_EQ(video_track->crop_right(), 0ull);
   DCHECK_EQ(video_track->crop_left(), 0ull);
   DCHECK_EQ(video_track->crop_top(), 0ull);