bug#57207: 29.0.50; Fontification is slow after e7b5912b23 (Improvements to long lines handling)

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: yantar92@gmail.com,  57207@debbugs.gnu.org
> Date: Thu, 18 Aug 2022 16:38:04 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> (progn
> >>   (pop-to-buffer "foo.txt")
> >>   (flyspell-mode)
> >>   (insert (propertize (make-string 20000 ?x) 'display "foo")
> >>      "\n\n"))
> >
> > Still no "Narrow" on the mode line.
> 
> Did you type a character after eval-ing that?

Yes.