gsk: Don't notify surface properties during render

The offloading may change subsurface stacking order, and thereby
change the effective dmabuf formats of the surface. But we don't
want to trigger callbacks during frame processing, so delay the
change notification until after we're done with that.

gsk/gskrenderer.c

@@ -483,6 +483,12 @@ gsk_renderer_render (GskRenderer          *renderer,
   if (priv->surface == NULL)
     return;
 
+  /* Offloading can change subsurface stacking, which may trigger
+   * surface property changes. We don't want them to take effect
+   * during frame processing.
+   */
+  g_object_freeze_notify (G_OBJECT (priv->surface));
+
   renderer_class = GSK_RENDERER_GET_CLASS (renderer);
 
   clip = cairo_region_copy (region);
@@ -528,6 +534,8 @@ gsk_renderer_render (GskRenderer          *renderer,
   cairo_region_destroy (clip);
   g_clear_pointer (&offload, gsk_offload_free);
   priv->prev_node = gsk_render_node_ref (root);
+
+  g_object_thaw_notify (G_OBJECT (priv->surface));
 }
 
 /*< private >