Oh right, this previously logic was silly: we can't count on the
*interval itself* to be reliably resetting the FPS counter state,
because the interval might not be firing!
I think this fix worked when I tried brief tests, but didn't work when
I did an (accidental) longer test, because the browser switched to a
more aggressive throttle mode, and the previous mode was close enough
on the resets for it to be fine, whereas this time the FPS counter
state got way too old.
Now, we reset the FPS counter state *exactly* when the page comes back.
Emi Matchu
56fe5e4889