Support multiple media tracks in MSE / ChunkDemuxer

media/base/media_track.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/base/media_track.h"
 
 namespace media {
 
 MediaTrack::MediaTrack(Type type,
                        StreamParser::TrackId bytestream_track_id,
                        const std::string& kind,
                        const std::string& label,
                        const std::string& lang)
     : type_(type),
       bytestream_track_id_(bytestream_track_id),
       kind_(kind),
       label_(label),
       language_(lang) {}
 
 MediaTrack::~MediaTrack() {}
 
+const char* TrackTypeToStr(MediaTrack::Type type) {
+  switch (type) {
+    case MediaTrack::Audio:
+      return "audio";
+    case MediaTrack::Text:
+      return "text";
+    case MediaTrack::Video:
+      return "video";
+  }
+  NOTREACHED();
+  return "INVALID";
+}
+
 }  // namespace media