Make FakeChromeUserManager subclass of ChromeUserManager

chrome/browser/chromeos/login/users/scoped_user_manager_enabler.h

 // Copyright 2014 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_USERS_SCOPED_USER_MANAGER_ENABLER_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_USERS_SCOPED_USER_MANAGER_ENABLER_H_
 
 #include "base/macros.h"
 
 namespace user_manager {
 class UserManager;
 }
 
 namespace chromeos {
 
+class ChromeUserManager;
+
 // Helper class for unit tests. Initializes the UserManager singleton to the
 // given |user_manager| and tears it down again on destruction. If the singleton
 // had already been initialized, its previous value is restored after tearing
 // down |user_manager|.
 class ScopedUserManagerEnabler {
  public:
   // Takes ownership of |user_manager|.
-  explicit ScopedUserManagerEnabler(user_manager::UserManager* user_manager);
+  explicit ScopedUserManagerEnabler(ChromeUserManager* user_manager);
   ~ScopedUserManagerEnabler();
 
  private:
   user_manager::UserManager* previous_user_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedUserManagerEnabler);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_USERS_SCOPED_USER_MANAGER_ENABLER_H_