Canvas.requestAnimationFrame's callback uses seconds instead of milliseconds

I've just ported some web-javascript code to QML and noticed that the callback's timestamp parameter of requestAnimationFrame is in seconds instead of milliseconds like on all major browsers.

Receiving the same timestamp 60 times per second makes no sense at all.

Since this is a behavior-change, the non-existing documentation mentioned in QTBUG-46554 also needs to be updated.