diff -upr marco/src/core/atomnames.h marco-test-master/src/core/atomnames.h
--- marco/src/core/atomnames.h	2015-10-06 17:15:54.909757371 +0200
+++ marco-test-master/src/core/atomnames.h	2015-10-23 17:19:23.373005831 +0200
@@ -58,7 +58,6 @@ item(_MARCO_RESTART_MESSAGE)
 item(_MARCO_RELOAD_THEME_MESSAGE)
 item(_MARCO_SET_KEYBINDINGS_MESSAGE)
 item(_MARCO_TOGGLE_VERBOSE)
-item(_GTK_FRAME_EXTENTS)
 item(_MATE_PANEL_ACTION)
 item(_MATE_PANEL_ACTION_MAIN_MENU)
 item(_MATE_PANEL_ACTION_RUN_DIALOG)
@@ -71,6 +70,7 @@ item(MULTIPLE)
 item(TIMESTAMP)
 item(VERSION)
 item(ATOM_PAIR)
+item(_GTK_FRAME_EXTENTS)
 
 /* Oddities: These are used, and we need atoms for them,
  * but when we need all _NET_WM hints (i.e. when we're making
diff -upr marco/src/core/constraints.c marco-test-master/src/core/constraints.c
--- marco/src/core/constraints.c	2015-10-06 17:15:54.910757381 +0200
+++ marco-test-master/src/core/constraints.c	2015-10-23 17:20:37.214737879 +0200
@@ -437,7 +437,7 @@ setup_constraint_info (ConstraintInfo
    */
 
   if (meta_prefs_get_force_fullscreen() &&
-      (window->decorated || !meta_window_is_client_decorated (window)) &&
+      window->decorated &&
       meta_rectangle_equal (new, &xinerama_info->rect) &&
       window->has_fullscreen_func &&
       !window->fullscreen)
diff -upr marco/src/core/window.c marco-test-master/src/core/window.c
--- marco/src/core/window.c	2015-10-23 17:18:23.157406594 +0200
+++ marco-test-master/src/core/window.c	2015-10-23 17:20:41.317778555 +0200
@@ -4058,18 +4058,7 @@ meta_window_get_outer_rect (const MetaWi
   if (window->frame)
     *rect = window->frame->rect;
   else
-    {
-        *rect = window->rect;
-
-	if (window->has_custom_frame_extents)
-	  {
-	    const GtkBorder *extents = &window->custom_frame_extents;
-	    rect->x += extents->left;
-	    rect->y += extents->top;
-	    rect->width -= extents->left + extents->right;
-	    rect->height -= extents->top + extents->bottom;
-	  }
-    }
+    *rect = window->rect;
 }
 
 void
@@ -8468,20 +8457,3 @@ meta_window_is_maximized (MetaWindow *wi
   return META_WINDOW_MAXIMIZED (window);
 }
 
-/**
- * meta_window_is_client_decorated:
- *
- * Check if if the window has decorations drawn by the client.
- * (window->decorated refers only to whether we should add decorations)
- */
-gboolean
-meta_window_is_client_decorated (MetaWindow *window)
-{
-  /* Currently the implementation here is hackish -
-   * has_custom_frame_extents() is set if _GTK_FRAME_EXTENTS is set
-   * to any value even 0. GTK+ always sets _GTK_FRAME_EXTENTS for
-   * client-side-decorated window, even if the value is 0 because
-   * the window is maxized and has no invisible borders or shadows.
-   */
-  return window->has_custom_frame_extents;
-}
diff -upr marco/src/core/window-private.h marco-test-master/src/core/window-private.h
--- marco/src/core/window-private.h	2015-10-23 17:18:23.155406574 +0200
+++ marco-test-master/src/core/window-private.h	2015-10-23 17:20:41.320778585 +0200
@@ -356,9 +356,6 @@ struct _MetaWindow
    */
   MetaRectangle rect;
 
-  gboolean has_custom_frame_extents;
-  GtkBorder custom_frame_extents;
-
   /* The geometry to restore when we unmaximize.  The position is in
    * root window coords, even if there's a frame, which contrasts with
    * window->rect above.  Note that this gives the position and size
@@ -664,8 +661,6 @@ void meta_window_unset_demands_attention
 
 void meta_window_update_icon_now (MetaWindow *window);
 
-gboolean meta_window_is_client_decorated (MetaWindow *window);
-
 void meta_window_update_role (MetaWindow *window);
 void meta_window_update_net_wm_type (MetaWindow *window);
 
diff -upr marco/src/core/window-props.c marco-test-master/src/core/window-props.c
--- marco/src/core/window-props.c	2015-10-06 17:15:54.919757469 +0200
+++ marco-test-master/src/core/window-props.c	2015-10-23 17:20:35.921725060 +0200
@@ -215,66 +215,12 @@ reload_kwm_win_icon (MetaWindow    *wind
   reload_icon (window, window->display->atom__KWM_WIN_ICON);
 }
 
-static gboolean
-gtk_border_equal (GtkBorder *a,
-                  GtkBorder *b)
-{
-  return (a->left == b->left &&
-          a->right == b->right &&
-          a->top == b->top &&
-          a->bottom == b->bottom);
-}
-
-static void
-meta_window_set_custom_frame_extents (MetaWindow *window,
-                                      GtkBorder  *extents)
-{
-  if (extents)
-    {
-      if (window->has_custom_frame_extents && gtk_border_equal (&window->custom_frame_extents, extents))
-        return;
-
-      window->has_custom_frame_extents = TRUE;
-      window->custom_frame_extents = *extents;
-    }
-  else
-    {
-      if (!window->has_custom_frame_extents)
-        return;
-
-      window->has_custom_frame_extents = FALSE;
-      memset (&window->custom_frame_extents, 0, sizeof (window->custom_frame_extents));
-    }
-
-  meta_window_queue (window, META_QUEUE_MOVE_RESIZE);
-}
-
 static void
 reload_gtk_frame_extents (MetaWindow    *window,
                           MetaPropValue *value,
                           gboolean       initial)
 {
-  if (value->type != META_PROP_VALUE_INVALID)
-    {
-      if (value->v.cardinal_list.n_cardinals != 4)
-        {
-          meta_verbose ("_GTK_FRAME_EXTENTS on %s has %d values instead of 4\n",
-                        window->desc, value->v.cardinal_list.n_cardinals);
-        }
-      else
-        {
-          GtkBorder extents;
-          extents.left   = (int)value->v.cardinal_list.cardinals[0];
-          extents.right  = (int)value->v.cardinal_list.cardinals[1];
-          extents.top    = (int)value->v.cardinal_list.cardinals[2];
-          extents.bottom = (int)value->v.cardinal_list.cardinals[3];
-          meta_window_set_custom_frame_extents (window, &extents);
-        }
-    }
-  else
-    {
-      meta_window_set_custom_frame_extents (window, NULL);
-    }
+  return;
 }
 
 static void