Generate and assign media track ids in demuxers.

third_party/WebKit/public/platform/WebSourceBufferClient.h

 // Copyright 2014 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 WebSourceBufferClient_h
 #define WebSourceBufferClient_h
 
 #include "WebMediaPlayer.h"
 #include "WebString.h"
 #include "WebVector.h"
 
 namespace blink {
 
 class WebSourceBufferClient {
 public:
     virtual ~WebSourceBufferClient() { }
 
-    // Complete media track info: track type, bytestream id, kind, label, language.
+    // Complete media track info: track type, unique track id, kind, label, language.
     struct MediaTrackInfo {
         WebMediaPlayer::TrackType trackType;
-        WebString byteStreamTrackId;
+        WebMediaPlayer::TrackId id;
         WebString kind;
         WebString label;
         WebString language;
     };
 
     // Notifies SourceBuffer that parsing of a new init segment has been completed successfully. The input parameter is a collection
     // of information about media tracks found in the new init segment. The return value is a vector of blink WebMediaPlayer track ids
     // assigned to each track of the input collection (the order of output track ids must match the input track information).
     virtual WebVector<WebMediaPlayer::TrackId> initializationSegmentReceived(const WebVector<MediaTrackInfo>& tracks) = 0;
 };
 
 } // namespace blink
 
 #endif // WebSourceBufferClient_h