Miscellany

GOOGLE_NOT_SUPPORTED        => NS_ERROR_NOT_IMPLEMENTED
GOOGLE_INVALID_URI          => NS_ERROR_MALFORMED_URI
GOOGLE_INVALID_XML          => NS_ERROR_DOM_SYNTAX_ERR

GOOGLE_XML_MISSING_FEED     => NS_ERROR_DOM_NOT_FOUND_ERR
GOOGLE_XML_MISSING_CHILDREN => NS_ERROR_DOM_NOT_FOUND_ERR
GOOGLE_LOGIN_CANCELED       => NS_ERROR_NOT_AVAILABLE

The only custom error left is GOOGLE_LOGIN_FAILED.