Writer pages always have an offset inside the root frame, and this is
visible in the generated metafile as well. The offset is minimal for a
small window and a single page, but the vertical offset increases with
every page. Make this information visible, so sfx2 can compensate this.

This is somewhat similar to what SfxObjectShell::DoDraw_Impl() does, but
that works for the first page only (use case is thumbnail generation),
while this is 0 offset for Calc/Impress and a proper offset for all
Writer pages.

Change-Id: I1075c98faf74f9e77c916572b4d63d40fbd80ab1
Reviewed-on: https://gerrit.libreoffice.org/65850Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
Tested-by: Jenkins