compositor: flush the batched up damage when shm buffer is destroyed

Since we now batch up damage and only handle it at repaint time, we need
to apply it in case a buffer is destroyed so we don't lose it.

Ander found the problem, but we need to fix it in the compositor so we
don't change the behavior of the compositor.

src/compositor.c

@@ -179,6 +179,9 @@ weston_client_launch(struct weston_compositor *compositor,
 	return client;
 }
 
+static void
+update_shm_texture(struct weston_surface *surface);
+
 static void
 surface_handle_buffer_destroy(struct wl_listener *listener, void *data)
 {
@@ -186,6 +189,9 @@ surface_handle_buffer_destroy(struct wl_listener *listener, void *data)
 		container_of(listener, struct weston_surface, 
 			     buffer_destroy_listener);
 
+	if (es->buffer && wl_buffer_is_shm(es->buffer))
+		update_shm_texture(es);
+
 	es->buffer = NULL;
 }