The range for which
   * |breakdownTree| is calculated.
   */
  function addIdleAndBlockByNetworkBreakdown_(breakdownTree, mainThreadEvents,
      networkEvents, rangeOfInterest) {
    const mainThreadEventRanges = tr.b.math.convertEventsToRanges(
        mainThreadEvents);
    const networkEventRanges = tr.b.math.convertEventsToRanges(
        networkEvents);
    const eventRanges = mainThreadEventRanges.concat(networkEventRanges);
    const idleRanges =
        tr.b.math.findEmptyRangesBetweenRanges(event