The simple answer is no. But the more complicated answer (as a Firefox developer looked into doing this a while ago), is that Keychain is pretty limiting about what you can (easily) store. Our heuristics require that we store more information about logins (for example, the action url). It also restricts protocols, so we can't store password for chrome:// urls there.
Not to say it's never a possibility, but it's not just because we don't want to!