[gtk+] Remove overhead in gdk_window_get_user_data

[Matthias Clasen <matthiasc src gnome org>]

commit 65ec902df9d5e0880fce44d5a9afc33c008b009b
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Sep 27 14:06:27 2015 -0400

    Remove overhead in gdk_window_get_user_data
    
    This function is called very frequently during in GTK+'s drawing
    paths, and thus should not carry unexpected costs.

 gdk/gdkwindow.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)
---
diff --git a/gdk/gdkwindow.c b/gdk/gdkwindow.c
index 2f7ee2d..75d1034 100644
--- a/gdk/gdkwindow.c
+++ b/gdk/gdkwindow.c
@@ -2174,8 +2174,6 @@ void
 gdk_window_get_user_data (GdkWindow *window,
                          gpointer  *data)
 {
-  g_return_if_fail (GDK_IS_WINDOW (window));
-
   *data = window->user_data;
 }