Made a ScopedMockUserManagerEnabler to simplify UserManager mocking life-cycle.

chrome/browser/chromeos/login/mock_user_manager.h

 // Copyright (c) 2012 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_MOCK_USER_MANAGER_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_MOCK_USER_MANAGER_H_
 #pragma once
 
 #include <string>
 
@@ skipping 50 matching lines @@
   // You can't mock this function easily because nobody can create User objects
   // but the UserManagerImpl and us.
   virtual User& GetLoggedInUser() OVERRIDE;
 
   // Sets a new User instance.
   void SetLoggedInUser(const std::string& email, bool guest);
 
   User* user_;
 };
 
+// Class that provides easy life-cycle management for mocking the UserManager
+// for tests.
+class ScopedMockUserManagerEnabler {
+ public:
+  ScopedMockUserManagerEnabler();
+  ~ScopedMockUserManagerEnabler();
+
+  MockUserManager* user_manager();
+
+ private:
+  UserManager* old_user_manager_;
+  scoped_ptr<MockUserManager> user_manager_;
+};
+
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_MOCK_USER_MANAGER_H_