we were reusing the stride of the surface we were cloning,
but the new surface has a different underlying size.

remove the custom stride argument and just change our stride
calculation to use the same scheme that cairo and GDI uses, which
remove another platform/drawing-system variable

Change-Id: I257dac9757b121642e9ccfde7db0911edc9f3fb1
Reviewed-on: https://gerrit.libreoffice.org/20149Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>