bug#13476: 24.3.50; Reverting scroll-bar face customization has no effect

[Eli Zaretskii]

> From: Mauro Aranda <maurooaranda@gmail.com>
> Cc: eliz@gnu.org,  13476@debbugs.gnu.org,  stephen.berman@gmx.net
> Date: Mon, 28 Feb 2022 09:59:15 -0300
> 
> > --- a/lisp/faces.el
> > +++ b/lisp/faces.el
> > @@ -1743,7 +1743,14 @@ The following sources are applied in this order:
> >          (and tail (face-spec-set-2 face frame
> >                                     (list :extend (cadr tail))))))
> >      (setq face-attrs (face-spec-choose (get face 'face-override-spec) 
> > frame))
> > -    (face-spec-set-2 face frame face-attrs)))
> > +    (face-spec-set-2 face frame face-attrs)
> > +    (when (and (fboundp 'set-frame-parameter) ; This isn't available
> > +                                              ; during loadup.
> > +               (eq face 'scroll-bar))
> > +      ;; Set the `scroll-bar-foreground' and `scroll-bar-background'
> > +      ;; frame parameters.  (bug#13476)
> > +      (set-frame-parameter frame 'scroll-bar-foreground (face-foreground 
> > face))
> > +      (set-frame-parameter frame 'scroll-bar-background (face-background 
> > face)))))

Why do we need this special treatment of the scroll-bar face?