wayland: Drop cairo surfaces when withdrawing

wayland: Drop cairo surfaces when withdrawing

If a window is unmapped by the client while gdk is processing updates,
(for example Firefox un-mapping its window on Expose events), the
windowing backend resources might be lost (for example with Wayland)
which can cause a crash in end_paint().

Make sure we drop the cairo surfaces as well when hiding the surface,
that will avoid the crash in gdk_window_impl_wayland_end_paint() when
trying to attach the staging cairo surface to a released wl_surface,
these will be recreated when needed when the surface becomes visible
again and there is no need to keep such buffers around for a surface
which is not visible anyway.

Bug: https://bugzilla.gnome.org/show_bug.cgi?id=793062
Origin: upstream, 3.22.30, commit:3bd7b379c8d2c7e57ce22501420791c4bfcf24ca

Gbp-Pq: Name 0013-wayland-Drop-cairo-surfaces-when-withdrawing.patch