So that we can turn on theming in runtime. Otherwise, themed dialog and scrollbar
are not enabled even if a theme is made active in winecfg if theming is disabled at start.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=44511Signed-off-by: Zhiyi Zhang <zzhang@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>