am e71da1f7: Merge "MatroskaExtractor: use GetTrackByNumber instead of GetTrackByIndex" into lmp-mr1-dev automerge: a7e65b1

* commit 'e71da1f76a624adf97ca255149a85940a8515941':
  PlaylistFetcher: clear mStartup for .aac playlists after seek
  MatroskaExtractor: use GetTrackByNumber instead of GetTrackByIndex