code: function (el, setFocus) {
              var children,
                  cssClass = this.CLASSES,
                  grandParent,
                  parent   = el.parentNode;
  
              if (!parent) {
                  return;
              }
              grandParent = parent.parentNode;
  
              if (el.nodeName.toUpperCase() == "BUTTON" &&
                  Dom.hasClass(parent, cssClass.BUTTON)) {
                  if (setFocus) {
                      if (grandParent) {
                          children = Dom.getChildren(grandParent);
                          if (children) {
                              Dom.removeClass(children, cssClass.FOCUSSED_BUTTON);
                          }
                      }
                      Dom.addClass(parent, cssClass.FOCUSSED_BUTTON);
                  } else {
                      Dom.removeClass(parent, cssClass.FOCUSSED_BUTTON);
                  }
              }
          }
docs: Set the correct class for the navigation buttons.
  
  @method _updateNavButtons
  @param el {Object} The target button
  @param setFocus {Boolean} True to set focus ring, false otherwise.
  @protected