The initial implementation appears to be targeted to e-commerce sites. Your username and password are not included in the fields that this can populate.

Here are the supported fields:

* Contact: name, tel, email

* Shipping: street-address, address-line1, address-line2, locality, region, country, postal-code

* Billing: street-address, address-line1, address-line2, locality, region, country, postal-code

* Payment: cc-name, cc-number, cc-exp, cc-csc, cc-type