[gtk/wip/chergert/quartz4u: 79/120] macos: make GdkMacosSurface abstract

[Christian Hergert <chergert src gnome org>]

commit e37cf60179e7612c3d572d21d81635e56a01bc92
Author: Christian Hergert <chergert redhat com>
Date:   Tue May 19 17:43:45 2020 -0700

    macos: make GdkMacosSurface abstract
    
    We only use subclasses of this.

 gdk/macos/gdkmacossurface.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gdk/macos/gdkmacossurface.c b/gdk/macos/gdkmacossurface.c
index 9e384a20e4..11a2e1fabe 100644
--- a/gdk/macos/gdkmacossurface.c
+++ b/gdk/macos/gdkmacossurface.c
@@ -39,7 +39,7 @@
 #include "gdkmacostoplevelsurface-private.h"
 #include "gdkmacosutils-private.h"
 
-G_DEFINE_TYPE (GdkMacosSurface, gdk_macos_surface, GDK_TYPE_SURFACE)
+G_DEFINE_ABSTRACT_TYPE (GdkMacosSurface, gdk_macos_surface, GDK_TYPE_SURFACE)
 
 enum {
   PROP_0,