 {
        this._updateItems();

        if (this._shouldUpdateSelection) {
          this._updateSelected();
        }

        // Let other interested parties know about the change so that
        // we don't have to recreate mutation observers everywhere.
        this.fire('iron-items-changed', mutations, {
          bubbles: false,
          cancelable: false
        });
      });
    },

    _activateHandler: function(e) {
      var t = e.target;
      var items = this.items;
      while (t && t != thi