Polymer 1.0: google-signin sign in still success when user revoke permissions

I am using a google-signin element to have access to user's access scopes. I found, if I as a user authorize the my app with certain scopes, then revoke those scopes without clicking on "Sign out" button (basically the google-signin element), the google-sign is result as onSigninSuccess event even without the authorization.

This is weird. It should be onSigninFailure because the app doesn't have the corresponding scopes of authorizations from the user.

via Chebli Mohamed