If the display has been setup up, we should destroy the underlying
objects that the winsys has created. This can be done by calling the
winsys->destroy_display() function in _free.
Then, in that function, and for the NULL and GDL EGL platform we can
destroy the surface we have created in the setup_display() function
(through create_context()).
This allows to have clutter create a "dummy" display in
cogl_renderer_check_onscreen_template(), then free it, then recreate the
context and the surface that will be the final ones.
https://bugzilla.gnome.org/show_bug.cgi?id=655355
d4dc51849e