[Jon]

It's a bit different on 4.4 but the principle is the same, just the exact code is a bit different. Probably this would work:

FIND:

$smarty->assign('ImagesDir',        $xcart_web_dir . $smarty_skin_dir . '/images');
$smarty->assign('SkinDir',          $xcart_web_dir . $smarty_skin_dir);

REPLACE WITH:

// WCM - MaxCDN Implementation
if ($_SERVER['HTTPS'] != 'on')
{
$smarty->assign('ImagesDir', 'http://CdnUrl.example.com//images');
$smarty->assign('SkinDir', 'http://CdnUrl.example.com/');
}
else
{
$smarty->assign('ImagesDir',        $xcart_web_dir . $smarty_skin_dir . '/images');
$smarty->assign('SkinDir',          $xcart_web_dir . $smarty_skin_dir);
}
// WCM - MaxCDN Implementation