If there's an onlineupgrade.php, installer index.php will link to that instead of upgrade.php (future readiness ;))
/*
* Auto-completing page/username fields
* NOTE: A more efficient version of the username field is used for Mozilla browsers. The updated code is in autofill.js.
*/
//
// **** 1.1.5: DEPRECATED ****
// Replaced with jQuery-based mechanism.
//