Records a lap, measuring the time since the previous lap (or the timer's start).
A descriptive name for this segment (e.g. 'db query', 'render').
The PerfTimerLap that was just recorded.
Stops the timer and returns all recorded laps along with the total elapsed time.
After calling stop(), further calls to PerfTimer.lap continue from the
last lap mark, not the stop point.
A PerfTimerResult containing all laps and the total duration.
A running performance timer created by createPerfTimer.