BeginMs| after searchBegin.
   *
   * Required quiet window size is modeled as an exponential decay. See
   * https://goo.gl/kQXGLW for development of the exact equation used here.
   *
   * @param {number} timeSinceSearchBeginMs - Time since the beginning of search
   *     window for First CPU Idle.
   */
  function requiredFCIWindowSizeMs(timeSinceSearchBeginMs) {
    const timeCoefficient = 1 / 15 * Math.log(2);

    const timeSinceSearchBeginSeconds = tr.b.convertUnit(timeSinceSearchBeginMs,
        tr