[gtk+] Avoid an extra type check in gdk_screen_get_default

[Matthias Clasen <matthiasc src gnome org>]

commit f5fe1e3a06b6ea9160f9b05aaadd228a813bafb9
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Sep 7 03:18:04 2015 -0400

    Avoid an extra type check in gdk_screen_get_default
    
    Just go through the vfunc directly.

 gdk/gdkdisplaymanager.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/gdk/gdkdisplaymanager.c b/gdk/gdkdisplaymanager.c
index ceb3fcc..bc3471f 100644
--- a/gdk/gdkdisplaymanager.c
+++ b/gdk/gdkdisplaymanager.c
@@ -363,12 +363,12 @@ gdk_display_get_default (void)
 GdkScreen *
 gdk_screen_get_default (void)
 {
-  GdkDisplay *default_display;
+  GdkDisplay *display;
 
-  default_display = gdk_display_get_default ();
+  display = gdk_display_get_default ();
 
-  if (default_display)
-    return gdk_display_get_default_screen (default_display);
+  if (display)
+    return GDK_DISPLAY_GET_CLASS (display)->get_default_screen (display);
   else
     return NULL;
 }