message: add onDisplayableFlushed();
diff: @@ -82,8 +82,11 @@ IncrementalDisplayble.prototype.brush = function (ctx, prevEl) {
  for (var i = 0; i < this._temporaryDisplayables.length; i++) {
  this._temporaryDisplayables[i].brush(ctx, i === 0 ? null : this._temporaryDisplayables[i - 1]);
  }
  +
  this._temporaryDisplayables = [];
  this._needsClear = false;
  +
  + this.onDisplaybleFlushed && this.onDisplaybleFlushed();
  };
  var m = [];
  