code: function(isChecked) {
          var view     = this.views[0],
              headerCt = view.headerCt,
              checkHd  = headerCt.child('gridcolumn[isCheckerHd]'),
              cls = this.checkerOnCls;
  
          if (checkHd) {
              if (isChecked) {
                  checkHd.addCls(cls);
              } else {
                  checkHd.removeCls(cls);
              }
          }
      }
docs: Toggle the ui header between checked and unchecked state.
  @param {Boolean} isChecked
  @private