bug#74435: Scrollbar width is not respected on Windows

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 21 Nov 2024 23:21:05 +0100
> Cc: johann.hoechtl@gmail.com, 74435@debbugs.gnu.org
> From: Cecilio Pardo <cpardo@imayhem.com>
> 
> I have tracked (I think) this problem to the function 
> frame.c:gui_set_scroll_bar_width
> 
> If the new value for the scrollbars width is equal to the current one, 
> then it resets width to the default size.
> 
> The 'if' tests for arg != FRAME_CONFIG_SCROLL_BAR_WIDTH(f).
> That is, if arg is equal to current width, the 'else' path is taken, 
> which resets to default.
> 
> I suppose this should test for arg != "DEFAULT_WIDTH", but I don't know 
> where to find that.

Thanks.  I'd like to look into this, but it would help if I could
reproduce the issue.

> Maybe you could not reproduce it because your scrollbars are on the 
> default size?

Maybe.  The OP didn't seem to say it was necessary to specify
non-default scroll-bar width.

So what is the minimum recipe for reproducing the issue?