clear method

Implementation

@override
clear([int filter = DanmuFlag.all]) {
  for (var scrollRow in scrollRows) {
    scrollRow.removeWhere((element) => filter.pick(element.flag));
  }
  for (int i = 0; i < centerRows.length; i++) {
    centerRows.removeWhere(
        (element) => element == null ? true : filter.pick(element.flag));
  }
}