function _trackFID() {
  return instrument.addFidInstrumentationHandler(({ metric }) => {
    const entry = metric.entries[metric.entries.length - 1];
    if (!entry) {
      return;
    }

    const timeOrigin = msToSec(utils.browserPerformanceTimeOrigin );
    const startTime = msToSec(entry.startTime);
    debugBuild.DEBUG_BUILD && utils.logger.log('[Measurements] Adding FID');
    _measurements['fid'] = { value: metric.value, unit: 'millisecond' };
    _measurements['mark.fid'] = { value: timeOrigin + startTime, unit: 'second' };
  });
}
Starts tracking the First Input Delay on the current page.