Happens only with when double buffering is enabled, and e.g. with the
oxygen GTK2 theme, but not with the default one.

Change-Id: Iad9911121e57388c84c25860413763f75e06b0ea
(cherry picked from commit 12d1a2a0)
Reviewed-on: https://gerrit.libreoffice.org/16931Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>