Form submit handler for form_state_values_clean() test form.
function form_test_form_state_values_clean_form_submit($form, &$form_state) {
form_state_values_clean($form_state);
// This won't have a proper JSON header, but Drupal doesn't check for that
// anyway so this is fine until it's replaced with a JsonResponse.
print drupal_json_encode($form_state['values']);
exit;
}