[metacity] compositor: simplify create_root_buffer

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 2906a4a7de5fa16cf0da6a8f381496b6546e7b5d
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Sat Mar 4 18:33:57 2017 +0200

    compositor: simplify create_root_buffer

 src/compositor/meta-compositor-xrender.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)
---
diff --git a/src/compositor/meta-compositor-xrender.c b/src/compositor/meta-compositor-xrender.c
index c823650..74fd5d1 100644
--- a/src/compositor/meta-compositor-xrender.c
+++ b/src/compositor/meta-compositor-xrender.c
@@ -910,8 +910,7 @@ static Picture
 create_root_buffer (MetaCompositorXRender *xrender,
                     MetaScreen            *screen)
 {
-  MetaDisplay *display = meta_screen_get_display (screen);
-  Display *xdisplay = meta_display_get_xdisplay (display);
+  Display *xdisplay = xrender->xdisplay;
   Picture pict;
   XRenderPictFormat *format;
   Pixmap root_pixmap;