Implement users options handling in login screen.

chrome/browser/chromeos/login/user_manager.h

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_CHROMEOS_LOGIN_USER_MANAGER_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_USER_MANAGER_H_
 #pragma once
 
 #include <string>
 #include <vector>
@@ skipping 51 matching lines @@
   // Indicates that user just started off the record session.
   void OffTheRecordUserLoggedIn();
 
   // Indicates that a user with the given email has just logged in.
   // The persistent list will be updated accordingly.
   void UserLoggedIn(const std::string& email);
 
   // Remove user from persistent list. NOTE: user's data won't be removed.
   void RemoveUser(const std::string& email);
 
+  // Returns true if given user has logged into the device before.
+  bool IsKnownUser(const std::string& email);
+
   // Returns the logged-in user.
   const User& logged_in_user() {
     return logged_in_user_;
   }
 
   // Sets image for logged-in user and sends LOGIN_USER_IMAGE_CHANGED
   // notification about the image changed via NotificationService.
   void SetLoggedInUserImage(const SkBitmap& image);
 
   // Saves image to file and saves image path in local state preferences.
@@ skipping 38 matching lines @@
   bool current_user_is_owner_;
 
   NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(UserManager);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_USER_MANAGER_H_