.createElement('tr-v-ui-histogram-span');
        this.histogramSpan_.viewState = this.viewState;
        this.histogramSpan_.rowState = this.row.viewState;
        this.histogramSpan_.rootState = this.row.rootViewState;
        this.histogramSpan_.build(this.histogram, this.referenceHistogram);
        this.$.histogram.appendChild(this.histogramSpan_);
      }

      this.viewState.isOpen = open;
    },

    onViewStateUpdate_(event) {
      if (event.delta.isOpen) {
        this.isHistogramOpen = this.vie