At a glance I didn't see anything for that. I would suggest looking at measures such as Time to First Byte (TTFB) which reflects when the client starts to receive the response as well as "Visually Complete" which will be when the visual window in the client's browser has fully rendered and thus would be better to determine user experience than Time to first paint (when the first pixel has loaded). There's plenty of other timings available as well, I would look at creating.
Because new research shows that there is a lag between the TTFB and First paint, this metric seems something that I would want to track. While I find it helpful to know the visually complete, the first paint would really be good to know.