get Tracks
Returns the list of tracks.
Return
A non-null List of Bundle objects, each representing a track. For text tracks ("SandboxedPlayer.TRACK_TYPE_TEXT"), the Bundle includes an "id" (integer index) and "sourceId" (string source description). For video ("SandboxedPlayer.TRACK_TYPE_VIDEO") and audio ("SandboxedPlayer.TRACK_TYPE_AUDIO") tracks, the Bundle includes only an "id".