ay = open ? 'none' : 'flex';
      this.$.open_histogram.style.display = open ? 'none' : 'block';

      this.$.close_histogram.style.display = open ? 'block' : 'none';
      this.$.histogram.style.display = open ? 'block' : 'none';

      // Wait to create the histogram-span until the user wants to display it
      // in order to speed up creating lots of histogram-set-table-cells when
      // building the table.
      if (open && this.histogramSpan_ === undefined) {
        this.histogramSpan_ = document