[mutter/gnome-3-28] wayland/xdg-shell: Cache frame callbacks if toplevel is unmanaged

[Olivier Fourdan <ofourdan src gnome org>]

commit b5c2555601da7c8b347664e7ef34803e08a52697
Author: Jonas Ådahl <jadahl gmail com>
Date:   Mon Aug 27 12:30:07 2018 +0200

    wayland/xdg-shell: Cache frame callbacks if toplevel is unmanaged
    
    A toplevel window can be unmanaged without the client knowing it (e.g. a
    modal dialog being unmapped together with its parent. When this has
    happened, take frame callbacks queued on a commit and cache them on the
    generic surface queue. If the toplevel is to be remapped, either because
    the surface was reassigned the toplevel role, or if it was reset and
    remapped, the cached frame callbacks will be queued on the surface actor
    and dispatched accordingly.
    
    https://gitlab.gnome.org/GNOME/mutter/issues/240
    (cherry picked from commit 80d420ff430e8e9495fd29d68084cb050600b26f)

 src/wayland/meta-wayland-xdg-shell.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
---
diff --git a/src/wayland/meta-wayland-xdg-shell.c b/src/wayland/meta-wayland-xdg-shell.c
index 3cf6b5716..9e300df6b 100644
--- a/src/wayland/meta-wayland-xdg-shell.c
+++ b/src/wayland/meta-wayland-xdg-shell.c
@@ -624,6 +624,13 @@ meta_wayland_xdg_toplevel_commit (MetaWaylandSurfaceRole  *surface_role,
   MetaRectangle old_geometry;
   gboolean geometry_changed;
 
+  window = surface->window;
+  if (!window)
+    {
+      meta_wayland_surface_cache_pending_frame_callbacks (surface, pending);
+      return;
+    }
+
   if (!surface->buffer_ref.buffer && xdg_surface_priv->first_buffer_attached)
     {
       MetaWaylandActorSurface *actor_surface =
@@ -635,7 +642,6 @@ meta_wayland_xdg_toplevel_commit (MetaWaylandSurfaceRole  *surface_role,
       return;
     }
 
-  window = surface->window;
   old_geometry = xdg_surface_priv->geometry;
 
   surface_role_class =