code: function() {
          if (this.resizeFrame) {
              var DOM    = YAHOO.util.Dom;
              var el     = this.getEl();
              var dragEl = this.getDragEl();
  
              var bt = parseInt( DOM.getStyle(dragEl, "borderTopWidth"    ), 10);
              var br = parseInt( DOM.getStyle(dragEl, "borderRightWidth"  ), 10);
              var bb = parseInt( DOM.getStyle(dragEl, "borderBottomWidth" ), 10);
              var bl = parseInt( DOM.getStyle(dragEl, "borderLeftWidth"   ), 10);
  
              if (isNaN(bt)) { bt = 0; }
              if (isNaN(br)) { br = 0; }
              if (isNaN(bb)) { bb = 0; }
              if (isNaN(bl)) { bl = 0; }
  
              this.logger.log("proxy size: " + bt + "  " + br + " " + bb + " " + bl);
  
              var newWidth  = Math.max(0, el.offsetWidth  - br - bl);                                                                                           
              var newHeight = Math.max(0, el.offsetHeight - bt - bb);
  
              this.logger.log("Resizing proxy element");
  
              DOM.setStyle( dragEl, "width",  newWidth  + "px" );
              DOM.setStyle( dragEl, "height", newHeight + "px" );
          }
      }
docs: The proxy is automatically resized to the dimensions of the linked
  element when a drag is initiated, unless resizeFrame is set to false
  @method _resizeProxy
  @private