title: GoogleWebAuthorizationBroker does not automatically return new access token from refresh token
body: <p>I use the GoogleWebAuthorizationBroker class form .Net Client library which stores an access token and a refresh token in the file storage, like this : </p>
  
  <pre><code>            UserCredential credential = GoogleWebAuthorizationBroker.AuthorizeAsync(
                 new ClientSecrets { ClientId = clientId, ClientSecret = clientSecret },
                                   scopes, "XXXXXX", CancellationToken.None
              ,new FileDataStore("XXXXXX")
                                  ).Result;
  </code></pre>
  
  <p>If works, but after one hour, when the acces token is invalid, when launching the AuthorizeAsync again, the access tokens returned in the "credential" object is not renewed, as it should be (I cheked the values in the debug mode and the acces token is still the same, not renewed). Even the browser does not launch to ask user for granting permission (i use it for the Google contacts API).</p>
  
  <p>I use OAuth2 with .Net google client library to authentificate, since is much simplier than then authentification with the gdata library.
  Nevertheless I use the old gdata lib to update gmail contacts (the new contact API does not allow YET contact data modification). </p>
  
  <p>Is there a problem with mixing those APIs ? Should i autentificate with the gdata library ? </p>
  
  <p>Thanx. </p>