title: Facebook login cached result issue
body: <p>I have use case that i need to get access token then request long lived access token. Below code achieve this use case but can't handle cached result.</p>
  
  <pre><code>FB.login(function (response) {
      if (response.status == 'connected')
          //sends token to server and server request long lived token.
  }, { scope: 'email,user_birthday' });
  </code></pre>
  
  <p>Server fails to request long lived token if user is logged out from the other tab. Because user is logged out and that short access token is invalidated but still <a href="https://developers.facebook.com/docs/reference/javascript/FB.login/" rel="nofollow">FB.login</a> brings invalidated cached token. I haven't found any parameter on <a href="https://developers.facebook.com/docs/reference/javascript/FB.login/" rel="nofollow">FB.login</a> for specifying not to cache result. </p>
  
  <p>But <a href="https://developers.facebook.com/docs/reference/javascript/FB.getLoginStatus/" rel="nofollow">FB.getLoginStatus</a> have parameter for not to cache result. So in this case, i pass second parameter as true to <a href="https://developers.facebook.com/docs/reference/javascript/FB.getLoginStatus/" rel="nofollow">FB.getLoginStatus</a> for not to having cached result. So inside that method if user is not logged in i call <a href="https://developers.facebook.com/docs/reference/javascript/FB.login/" rel="nofollow">FB.login</a> to prompt user login dialog. In this case true parameter remove cache problem and below code works perfectly fine except for one case. <a href="https://developers.facebook.com/docs/reference/javascript/FB.login/" rel="nofollow">FB.login</a> inside <a href="https://developers.facebook.com/docs/reference/javascript/FB.getLoginStatus/" rel="nofollow">FB.getLoginStatus</a> is blocked by browsers. </p>
  
  <p>How can i prevent browsers to not to block login dialog at below example or call <a href="https://developers.facebook.com/docs/reference/javascript/FB.login/" rel="nofollow">FB.login</a> directly without having cached result ? If both is not possible so is there another alternative solution ?</p>
  
  <pre><code>FB.getLoginStatus(function (response) {
      if (response.status == 'connected') {
          //sends token to server and server request long lived token.
      } else {
          FB.login(function (response) {
              if (response.status == 'connected'){
                //sends token to server and server request long lived token.       
              }         
          }, { scope: 'email,user_birthday' });
      }
  }, true);
  </code></pre>