[gnome-boxes] res-graph: Make use of GtkStyle.render_background()

[Zeeshan Ali Khattak <zeeshanak src gnome org>]

commit 134f29782663a1471ac7a2431823d029dbe7c875
Author: Zeeshan Ali (Khattak) <zeeshanak gnome org>
Date:   Tue Mar 15 18:21:30 2016 +0000

    res-graph: Make use of GtkStyle.render_background()
    
    https://bugzilla.gnome.org/show_bug.cgi?id=763677

 src/resource-graph.vala |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)
---
diff --git a/src/resource-graph.vala b/src/resource-graph.vala
index 38b74b8..958334b 100644
--- a/src/resource-graph.vala
+++ b/src/resource-graph.vala
@@ -33,9 +33,7 @@ private class Boxes.ResourceGraph: Gtk.DrawingArea {
         var height = get_allocated_height ();
         var style = get_style_context ();
 
-        Gdk.cairo_set_source_rgba (cr, style.get_background_color (get_state_flags ()));
-        cr.rectangle (0, 0, width, height);
-        cr.fill ();
+        style.render_background (cr, 0, 0, width, height);
 
         var nstep = (npoints == -1 ? points.length : npoints) - 1;
         var dy = 0.0;