bug#41200: Displaying a tooltip with x-show-tip gets very slow as more faces are defined

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Eli Zaretskii <eliz@gnu.org>, 41200@debbugs.gnu.org
> Date: Fri, 15 May 2020 10:03:44 -0400
> 
> I'm hoping it can make it into Emacs-27.1, tho it is probably rather
> late for such a significant change.

It's too late.  Such a significant change on such a low level is got
to cause some issues, especially as parts of it are
backward-incompatible.