Surface buffers are created with meta_drm_buffer_new_acquire(), taking a
gbm_surface acquiring the gbm itself, and meta_drm_buffer_new_take()
that takes over ownership of a passed gbm_bo.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/798
There is no reason why we should have an internal type enum when we have
all the infrastructure to just use multiple GObject types. Also there
was no code sharing between the old "types", the only common API was
getting the framebuffer ID, so lets make that a vfunc.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/584