as a true percentage value. 255 is a special flag that the value is synced to
the other dimension. Without this word gives the frame in the attached example
a huge height.

(cherry picked from commit b2ad33fd)

Change-Id: Ida0c15779d4583ca075428d77b8dc03c32f22edb
Reviewed-on: https://gerrit.libreoffice.org/18332Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>