Gdk: fix wrong user_data handling in resize_cairo_surface()

Instead of destroying the surface in the backend if this is
unable to resize, let the core code do it, and do it properly.

Based on a patch by Benjamin Otte.

https://bugzilla.gnome.org/show_bug.cgi?id=725172

gdk/broadway/gdkwindow-broadway.c

@@ -365,16 +365,14 @@ _gdk_broadway_window_destroy (GdkWindow *window,
 				       impl->id);
 }
 
-static cairo_surface_t *
+static gboolean
 gdk_window_broadway_resize_cairo_surface (GdkWindow       *window,
 					  cairo_surface_t *surface,
 					  gint             width,
 					  gint             height)
 {
   /* Image surfaces cannot be resized */
-  cairo_surface_destroy (surface);
-
-  return NULL;
+  return FALSE;
 }
 
 static void