amp of interest.
   * @param {number} networkQuietWindowStart - Most recent timestamp when the
   * renderer became network 2-quiet. Undefined if renderer is not network
   * 2-quiet at |timestamp|.
   * @param {number} mainThreadQuietWindowStart - End of most recent long task.
   * Undefined if a long task is in progress at |timestamp|.
   * @returns {boolean}
   */
  function reachedTTIQuiscence_(timestamp,
      networkQuietWindowStart, mainThreadQuietWindowStart) {
    if (networkQuietWindowStart === un