[gnome-boxes] app: Ensure windows hidden before suspending machines

[Zeeshan Ali Khattak <zeeshanak src gnome org>]

commit 9e68eb05414c782910b70f36b780edcb2a371273
Author: Zeeshan Ali (Khattak) <zeeshanak gnome org>
Date:   Mon Oct 12 17:23:34 2015 +0100

    app: Ensure windows hidden before suspending machines
    
    https://bugzilla.gnome.org/show_bug.cgi?id=755082

 src/app.vala |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/src/app.vala b/src/app.vala
index 2fe914a..51e66ca 100644
--- a/src/app.vala
+++ b/src/app.vala
@@ -267,6 +267,9 @@ private class Boxes.App: Gtk.Application {
     public bool quit_app () {
         foreach (var window in windows)
             window.hide ();
+        // Ensure windows are hidden before returning from this function
+        var display = Gdk.Display.get_default ();
+        display.flush ();
 
         Idle.add (() => {
             quit ();