Unlike in Writer, there doesn't seem to be an existing UNO API that can
be reused here.

Change-Id: I011a2f34d4d09ad604991637322ceadf6b2eb181
Reviewed-on: https://gerrit.libreoffice.org/28498Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>