Implements template_preprocess_HOOK() for overlay.tpl.php
If the current page request is inside the overlay, add appropriate classes to the <body> element, and simplify the page title.
overlay.tpl.php
function template_preprocess_overlay(&$variables) {
$variables['tabs'] = menu_primary_local_tasks();
$variables['title'] = drupal_get_title();
$variables['disable_overlay'] = overlay_disable_message();
// Add attributes for the overlay container.
$variables['attributes']['id'] = 'overlay';
$variables['attributes']['class'][] = 'overlay';
// Add attributes for the overlay title.
$variables['title_attributes']['id'] = 'overlay-title';
// Add attributes for the overlay content.
$variables['content_attributes']['id'] = 'overlay-content';
$variables['content_attributes']['class'][] = 'clearfix';
}