is
Determines if the SubtitleTrack should be selected by the player per default and kept in sync with theselected audio language. In that case the subtitle track will not appear in getAvailableSubtitles.Per default subtitle tracks with isForced set to true will be selected. In case of DASH these aresubtitles with the role `forced_subtitle` and in case of HLS subtitles with the attribute `FORCED=YES`.Is called when parsing new subtitle tracks.
Return
whether the passed SubtitleTrack should be considered as a forced subtitle.
Parameters
subtitleTrack
The SubtitleTrack for which isForced will be overwritten for.