code: function() {
              var tt = this;
              Dom.addClass(tt.underlay, "yui-force-redraw");
              setTimeout(function() {Dom.removeClass(tt.underlay, "yui-force-redraw");}, 0);
          }
docs: Forces the underlay element to be repainted, through the application/removal
  of a yui-force-redraw class to the underlay element.
  
  @method forceUnderlayRedraw