Firefox 81.0: disappearing tooltips

[Christian Weisgerber]

After the update of Firefox from 80.0.1 to 81.0, the display of
tooltips is broken for me.  They pop up and immediately disappear
again, too quick to read.  This affects tooltips on page content
and for the built-in PDF reader, but not those for the Firefox user
interface. (PR #249465)

Canonical test: I can no longer read the mouseover text on xkcd.com,
because it flashes by too quickly.

Is anybody else seeing this?
A conspicuous lack of screaming on the net suggests that it doesn't
affect everybody.

(FWIW, I observe the same problem on different hardware running
OpenBSD.)

-- 
Christian "naddy" Weisgerber                          naddy at mips.inka.de