Extract a new helper method `BuilderBase::isToolbarItemClass`
to identify whether a widget class is one of those used for
toolbar items.
Related: Gtk's GtkToolItem doc [1].
(But this commit just moves the existing logic without
looking into that Gtk doc further.)
[1] https://docs.gtk.org/gtk3/class.ToolItem.html
Change-Id: I1e39e4afb13db374ae77a3cdb6a4dd9eca7ee3ca
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/163957
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>
Michael Weghorn
625d22600d