Use StreamParser::TrackId instead of string for MediaTrack::byteStreamTrackId

media/base/media_track.h

 // 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.
 
 #ifndef MEDIA_BASE_MEDIA_TRACK_H_
 #define MEDIA_BASE_MEDIA_TRACK_H_
 
 #include <string>
 
 #include "media/base/media_export.h"
+#include "media/base/stream_parser.h"
 
 namespace media {
 
 class MEDIA_EXPORT MediaTrack {
  public:
   enum Type { Text, Audio, Video };
   MediaTrack(Type type,
-             const std::string& id,
+             StreamParser::TrackId id,
              const std::string& kind,
              const std::string& label,
              const std::string& lang);
   ~MediaTrack();
 
   Type type() const { return type_; }
 
-  const std::string& id() const { return id_; }
+  StreamParser::TrackId id() const { return id_; }
   const std::string& kind() const { return kind_; }
   const std::string& label() const { return label_; }
   const std::string& language() const { return language_; }
 
  private:
   Type type_;
-  std::string id_;
+  StreamParser::TrackId id_;
   std::string kind_;
   std::string label_;
   std::string language_;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_MEDIA_TRACK_H_