cogl_wayland_onscreen_get_surface previously only worked if the
onscreen had a foreign surface on it. However there is no reason why
this shouldn't also work fine for manipulating the surface that Cogl
created as well. We may want to consider adding a separate getter for
the foreign surface that can be used before the framebuffer is
allocated.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit 6bc12947a51224b70525893143bfe421723ce255)
3060d44365