Chromebooks use Google Chrome as their default web browser. They support Basic and NTLM schemes when using IWA; however, since Chrome books are not able to join Window's domains, users receive a pop-up window each time they are prompted for credentials. Blue Coat recommends that you increase the credential refresh time so the popup does not occur every five minutes (the default). IP and cookie surrogates work as well.
The following article from Google provides more detail: