button: Restore focus

The custom gadget draw function has the side effect of informing
the gadget machinery wether to draw focus or not. Bring the
draw function back, just for its boolean return value. We may
want to find a better solution for this.

gtk/gtkbutton.c

@@ -870,7 +870,7 @@ gtk_button_get_render_node (GtkWidget   *widget,
 {
   GskRenderNode *res = gtk_css_gadget_get_render_node (GTK_BUTTON (widget)->priv->gadget,
                                                        renderer,
-                                                       FALSE);
+                                                       gtk_widget_has_visible_focus (widget));
 
   if (res == NULL)
     return NULL;