We change views (using setView) a lot in case of LOK. Changing the view,
without this patch, leads to InitShow on the dialog which means
invalidation of the whole dialog even though there is nothing to
invalidate. This decreases performance as it increases the dialog paint
traffic through the LOK API. We don't need to hide the dialog once it's
opened in case of LOK.

This patch improves the multiview dialog performance considerably
(can easily be noticed in GTV).

Change-Id: If2b4ceb945ccd86da3d90bbbb0a0b9fbade43f30
Reviewed-on: https://gerrit.libreoffice.org/57401Reviewed-by: Jan Holesovsky <kendy@collabora.com>
Tested-by: Jan Holesovsky <kendy@collabora.com>