[metacity] tile-preview: avoid a deprecation warning

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 3380502064e141feed402b5d67576d50a05c50c1
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Wed Oct 26 01:45:09 2016 +0300

    tile-preview: avoid a deprecation warning

 src/ui/tile-preview.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/src/ui/tile-preview.c b/src/ui/tile-preview.c
index be3b2b5..671b46f 100644
--- a/src/ui/tile-preview.c
+++ b/src/ui/tile-preview.c
@@ -65,8 +65,12 @@ meta_tile_preview_draw (GtkWidget *widget,
     }
   else
     {
+      GdkRGBA black = {.0, .0, .0, 1.0};
       GdkRGBA white = {1.0, 1.0, 1.0, 1.0};
 
+      gdk_cairo_set_source_rgba (cr, &black);
+      cairo_paint (cr);
+
       gdk_cairo_set_source_rgba (cr, &white);
 
       cairo_rectangle (cr,
@@ -218,9 +222,6 @@ meta_tile_preview_show (MetaTilePreview *preview,
     {
       cairo_rectangle_int_t outer_rect, inner_rect;
       cairo_region_t *outer_region, *inner_region;
-      GdkRGBA black = {.0, .0, .0, 1.0};
-
-      gdk_window_set_background_rgba (window, &black);
 
       outer_rect.x = outer_rect.y = 0;
       outer_rect.width = preview->tile_rect.width;