This would create a com.sun.star.drawing.DiagramShape, and work with
that, but nobody implements such a service.

Change-Id: I32a63dd258a5f168e37c5926a832dadd45c2b179
Reviewed-on: https://gerrit.libreoffice.org/62371
Tested-by: Jenkins
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>