and reports
     * node data to |this.histogramSet_|.
     *
     * @param {!tr.b.MultiDimensionalViewNode} root - Root of the subtree.
     * @param {!Array.<!Array.<string>>} rootPath - Path of the subtree root
     * node with respect to |this.rootNode_|.
     */
    reportDataFromTree_(root, rootPath) {
      const rootPathString = stringifyPathName_(rootPath);
      if (this.visitedSet_.has(rootPathString)) return;
      this.visitedSet_.add(rootPathString);

      this.reportValuesFromNode_(root, root