title: requestNewReadPermission shows login page again iOS SDK
body: <p>When I request user_friends permission, login page is shown again. 
  Thanks in advance!</p>
  
  <p>Here is the code:</p>
  
  <pre><code>[FBSession.activeSession requestNewReadPermissions:[NSArray arrayWithObject:@"user_friends"] completionHandler:^(FBSession *session, NSError *error) {
  
  }];
  </code></pre>
  
  <p>Here is the scenario :
  I already login with a session also with some permission (but user_friends is not yet included) I login using WEBVIEW(do you think it affect that I Logged in using webview?)</p>
  
  <p>Then after I check if the user has a permission of user_friends. If the user do not have a user_friends permission. I will add a permission using the "requestNewReadPermission" but when I call the requestNEwReadPermission instead of showing a webview with confirming that the app needs the userfriends list, It shows the login page.</p>