xwayland/window: Queue damage after commits are allowed

Compositors may use XWAYLAND_ALLOW_COMMITS to communicate when Xwayland may or may not commit new buffers to a wl_surface. If commits are denied, then later allowed, we'll only get a buffer attached if there is actual damage posted, which might be long after.

This fixes an issue where the window manager would reparent a window while denying commits, then after reparenting, allow commits. The window in question belonged to a game and took several seconds produce the next frame, resulting in an empty window appearing as if it had just disappeared.

Signed-off-by: Jonas Ådahl jadahl@gmail.com