nl_tokens: Creates an instance of this class .
pl_tokens: function DescriptionsButton ( player , <mask> , ready ) { classCallCheck ( this , DescriptionsButton ) ; var _this = possibleConstructorReturn ( this , _TextTrackButton . call ( this , player , options , ready ) ) ; var tracks = player . textTracks ( ) ; var changeHandler = bind ( _this , _this . handleTracksChange ) ; tracks . addEventListener ( 'change' , changeHandler ) ; _this . on ( 'dispose' , function ( ) { tracks . removeEventListener ( 'change' , changeHandler ) ; } ) ; return _this ; }