MediaRecorder: use VideoTrackRecorder::GetPreferredCodecId() when available

content/renderer/media/video_track_recorder.h

Index: content/renderer/media/video_track_recorder.h
diff --git a/content/renderer/media/video_track_recorder.h b/content/renderer/media/video_track_recorder.h
index e1db7fcf3def5f98669a69c182051cc3f81a76dd..d0f2c2ad77ecd6798b6b3f045fe47bde27856efc 100644
--- a/content/renderer/media/video_track_recorder.h
+++ b/content/renderer/media/video_track_recorder.h
@@ -37,10 +37,12 @@ namespace content {
 class CONTENT_EXPORT VideoTrackRecorder
     : NON_EXPORTED_BASE(public MediaStreamVideoSink) {
  public:
+  // Do not change the order of codecs; add new ones right before LAST.
   enum class CodecId {
     VP8,
     VP9,
     H264,
+    LAST
   };
   class Encoder;
 
@@ -50,6 +52,8 @@ class CONTENT_EXPORT VideoTrackRecorder
                           base::TimeTicks capture_timestamp,
                           bool is_key_frame)>;
 
+  static CodecId GetPreferredCodecId();
+
   VideoTrackRecorder(CodecId codec,
                      const blink::WebMediaStreamTrack& track,
                      const OnEncodedVideoCB& on_encoded_video_cb,