message: checked_duration_since -> saturating_duration_since
  Summary: Minor code cleanup.
diff: @@ -395,7 +395,7 @@ mod summary {
  fn change(&mut self, time: Instant) {
  let old_time = self.last_changed;
  let ti = self.top_info();
  - ti.time += time.checked_duration_since(old_time).unwrap_or_default();
  + ti.time += time.saturating_duration_since(old_time);
  self.last_changed = time;
  }
  @@ -416,8 +416,7 @@ mod summary {
  let CallExit { time, .. } = call_exit;
  self.change(*time);
  let (name, time_rec, start) = self.call_stack.pop().unwrap();
  - self.info[name.0].time_rec =
  - time_rec + time.checked_duration_since(start).unwrap_or_default();
  + self.info[name.0].time_rec = time_rec + time.saturating_duration_since(start);
  }
  /// Process each ValueMem in their chronological order
  