e: if we found any wake-ups, the total duration of the trace is
    // guaranteed to be positive.
    var totalDurationSeconds = model.bounds.duration / 1000;
    var foundAnyWakeUps = false;
    for (var thread in allWakeUps) {
      var threadWakeUps = allWakeUps[thread];
      for (var reason in threadWakeUps) {
        threadWakeUps[reason].frequency /= totalDurationSeconds;
        foundAnyWakeUps = true;
      }
    }

    if (!foundAnyWakeUps) {
      result.addPair('wakeUps', null);
      return;
  