title: Given a Facebook access token, how can I get the permissions it has?
body: <p>One use case is the following.</p>
  
  <p>I ask for a Facebook access token to new users with the <code>offline_access</code> permission and I store it for later use. If the user remove in his settings the <code>offline_access</code> permission the token becomes invalid.</p>
  
  <p>I would like to be able to test (maybe using the graph API) if the token I have still have the permissions I asked for, without waiting the user to log out to try to make an API call.</p>