title: Google+ Oauth 2.0 - Logout works well BUT automatically login after refreshing webpage
body: <h2>Heading</h2>
  
  <p>I'm working on Google App Engine. Using Python with the webbapp2 framework. </p>
  
  <p>I use Google API to login e logout. It seems to work well. Login and logout are perfect. This is the Google official guide: <a href="https://developers.google.com/+/web/signin/" rel="nofollow">https://developers.google.com/+/web/signin/</a></p>
  
  <p>The problem is that just after being logged out refreshing the page the user will automatically logged-in again. </p>
  
  <p>This is <strong>Login Button</strong> with relative parameters: </p>
  
  <pre><code>    &lt;span
          class="g-signin"
          data-callback="signinCallback"
          data-clientid="##################.apps.googleusercontent.com"
          data-cookiepolicy="single_host_origin"
          data-requestvisibleactions="http://schemas.google.com/AddActivity"
          data-scope="https://www.googleapis.com/auth/plus.login https://www.googleapis.com/auth/userinfo.email"&gt;
          &lt;button type="button"&gt;GOOGLE+ LOGIN&lt;/button&gt;
      &lt;/span&gt;
  </code></pre>
  
  <p>This is <strong>Logout Button</strong>: </p>
  
  <pre><code>    &lt;button onclick="disconnectUser()"&gt;Disconnect&lt;/button&gt;
  </code></pre>
  
  <p>This is the <strong>Logout callback function</strong>: </p>
  
  <pre><code>&lt;script type="text/javascript"&gt;
          function disconnectUser(access_token) {
            var revokeUrl = 'https://accounts.google.com/o/oauth2/revoke?token=' +
                access_token;
  
            // Esecuzione di una richiesta GET asincrona.
            $.ajax({
              type: 'GET',
              url: revokeUrl,
              async: false,
              contentType: "application/json",
              dataType: 'jsonp',
              success: function(nullResponse) {
                // Esegui un'azione, l'utente è disconnesso
                // La risposta è sempre indefinita.
  
                  document.getElementById('signinButton').setAttribute('style', 'display: inherit');
                  document.getElementById('revokeButton').setAttribute('style', 'display: none');
              },
              error: function(e) {
                // Gestione dell'errore
                // console.log(e);
                // Puoi indirizzare gli utenti alla disconnessione manuale in caso di esito negativo
                // https://plus.google.com/apps
              }
            });
          }
          // È possibile attivare la disconnessione con un clic del pulsante
          $('#revokeButton').click(disconnectUser);
      &lt;/script&gt;
  </code></pre>
  
  <p><strong>What do you think? What could be the problem? Something concerning cookies setting?</strong> </p>