    this.row.rootViewState.alpha);
    },

    build(row, displayLabel, viewState) {
      this.row_ = row;
      this.displayLabel_ = displayLabel;
      this.viewState_ = viewState;
      this.histogram_ = this.row.columns.get(displayLabel);

      if (this.viewState) {
        // this.viewState is undefined when this.histogram_ is undefined.
        // In that case, onViewStateUpdate_ wouldn't be able to do anything
        // anyway.
        this.viewState.addUpdateListener(this.onViewStateUpdate_.bind(