[gtk+] tests: fix button underline in testassistant

[William Jon McCann <mccann src gnome org>]

commit b69ac965eaac7cf79f26dd57fab9edf3a83a3cf8
Author: William Jon McCann <william jon mccann gmail com>
Date:   Tue Jan 28 21:42:39 2014 -0500

    tests: fix button underline in testassistant
    
    https://bugzilla.gnome.org/show_bug.cgi?id=723212

 tests/testassistant.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/tests/testassistant.c b/tests/testassistant.c
index 75cfd59..f55cfcd 100644
--- a/tests/testassistant.c
+++ b/tests/testassistant.c
@@ -543,6 +543,7 @@ create_full_featured_assistant (GtkWidget *widget)
       gtk_window_set_default_size (GTK_WINDOW (assistant), 400, 300);
 
       button = gtk_button_new_with_label ("_Stop");
+      gtk_button_set_use_underline (GTK_BUTTON (button), TRUE);
       gtk_widget_show (button);
       gtk_assistant_add_action_widget (GTK_ASSISTANT (assistant), button);
       g_signal_connect (button, "clicked",