or undefined if no size is extracted from any container memory
   *     dump).
   */
  function buildMemoryChartSeries(memoryDumps, dumpSizeExtractor) {
    const dumpCount = memoryDumps.length;
    const idToTimestampToPoint = {};
    const idToName = {};

    // Extract the sizes of all components from each memory dump.
    memoryDumps.forEach(function(dump, index) {
      dumpSizeExtractor(dump, function addSize(id, size, opt_name) {
        let timestampToPoint = idToTimestampToPoint[id];
        if (ti