Thanks to Antonio Sacco's links, I was able to find:
https://www.googleapis.com/discovery/v1/apis/oauth2/v2/rest?fields=auth(oauth2(scopes))
It says these are the scopes available:
- https://www.googleapis.com/auth/plus.me (Know who you are on Google)
- https://www.googleapis.com/auth/userinfo.email (View your email address)
- https://www.googleapis.com/auth/userinfo.profile (View basic information about your account)