code: function(id, on) {
              var el = (lang.isString(id) ? this.getElement(id) : id);
              Dom.setStyle(el, "display", (on) ? "" : "none");
          }
docs: Returns the cached element reference.  If the id is not a string, it
  is assumed that it is an element and this is returned.
  @param id {string|HTMLElement} the element key, id, or ref
  @param on {boolean} hide or show.  If true, show
  @protected