bug#56607: 29.0.50; (setq auto-resize-tool-bars 'grow-only) has no effect (pgtk)

[Eli Zaretskii <eliz@gnu.org>]

> Cc: 56607@debbugs.gnu.org
> Date: Sun, 17 Jul 2022 08:57:37 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> 
> > Date: Sat, 16 Jul 2022 21:52:09 -0400
> > From: Richard Hansen <rhansen@rhansen.org>
> > 
> > emacs -Q
> > M-: (setq auto-resize-tool-bars 'grow-only) RET
> > C-s
> > 
> > The tool bar now shows a ridiculously oversized marine life ring icon on the "Help" button, and the height of the tool bar has grown to accommodate the icon's size.
> > 
> > C-g
> > 
> > Expected behavior: The tool bar reverts back to how it was before C-s was pressed, except its height stays the same.
> > 
> > Actual behavior: The tool bar reverts back to how it was before, including reverting to its original height.
> 
> I cannot reproduce this because on my system the Help button doesn't
> get the "ridiculously oversized marine life ring icon", so the tool
> bar doesn't resize.

FWIW, the basic functionality in the display engine does work.  I can
simulate the resizing of the tool bar with the following snippet:

  (setq old-map (copy-sequence tool-bar-map))
  (tool-bar-add-item-from-menu 'dired "splash")

If I then evaluate the below:

  (setq tool-bar-map (copy-sequence old-map))

the large icon disappears, and under auto-resize-tool-bars set to
grow-only the tool bar stays the same dimensions.

So if the tool bar is displayed by Emacs (as opposed to by a toolkit),
the auto-resizing works as expected.  I guess this is indeed a GTK
thing, since it doesn't heed our variables?