How to get Google+ App permission status

How to get Google+ App permission status

I've got a webiste where I want to offer people to login via facebook
or/and google+. When the user logs in with facebook, I want to show on a
user's profile page if the user also granted permissions to log in via
Google+.
I have an G+ access- and refresh token in a database. I tried to use the
G+ client's "setAccessToken()" function and afterwards
"isAccessTokenExpired()" to do a check. The problem is that
"setAccessToken()" expects the accessToken param as a JSON as you get it
if you log in with google+. So I think itœ not the right way...
Does anyone has an idea how to check if the user granted permissions to
log in (without logging in)?
Best regards ninsky