wState.isOpen;
      }
    },

    onRowStateUpdate_(event) {
      if (event.delta.isOverviewed === undefined) return;
      if (this.row.viewState.isOverviewed) {
        this.showOverview();
      } else {
        this.hideOverview();
      }
    },

    onRootStateUpdate_(event) {
      if (event.delta.referenceDisplayLabel &&
          this.histogramSpan_) {
        this.histogramSpan_.build(this.histogram, this.referenceHistogram);
      }

      if (event.delta.displayStatisticName ||
          event