docs: function tabView_undoCloseGroup(aSpec) {
      var spec = aSpec || {};
      var group = spec.group;
  
      if (!group) {
        throw new Error(arguments.callee.name + ": Group not specified.");
      }
  
      var undo = this.getElement({
        type: "group_undoButton",
        value: group
      });
      this._controller.click(undo);
  
      this.waitForGroupUndo({group: group});
    }