cros: Clean up SessionStateDelegate refs in Chrome

components/user_manager/user_manager.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 COMPONENTS_USER_MANAGER_USER_MANAGER_H_
 #define COMPONENTS_USER_MANAGER_USER_MANAGER_H_
 
 #include <string>
 
 #include "base/callback_forward.h"
@@ skipping 37 matching lines @@
 
     // Called when the profile image for the given user is downloaded.
     // |profile_image| contains the downloaded profile image.
     virtual void OnUserProfileImageUpdated(const User& user,
                                            const gfx::ImageSkia& profile_image);
 
    protected:
     virtual ~Observer();
   };
 
-  // TODO(nkostylev): Refactor and move this observer out of UserManager.
+  // TODO(xiyuan): Refactor and move this observer out of UserManager.
   // Observer interface that defines methods used to notify on user session /
   // active user state changes. Default implementation is empty.
   class UserSessionStateObserver {
    public:
     // Called when active user has changed.
     virtual void ActiveUserChanged(const User* active_user);
 
     // Called when another user got added to the existing session.
     virtual void UserAddedToSession(const User* added_user);
 
@@ skipping 319 matching lines @@
   friend class chromeos::ScopedUserManagerEnabler;
 
   // Same as Get() but doesn't won't crash is current instance is NULL.
   static UserManager* GetForTesting();
 
   // Sets UserManager instance to the given |user_manager|.
   // Returns the previous value of the instance.
   static UserManager* SetForTesting(UserManager* user_manager);
 };
 
+// TODO(xiyuan): Move this along with UserSessionStateObserver
+class USER_MANAGER_EXPORT ScopedUserSessionStateObserver {
+ public:
+  explicit ScopedUserSessionStateObserver(
+      UserManager::UserSessionStateObserver* observer);
+  ~ScopedUserSessionStateObserver();
+
+ private:
+  UserManager::UserSessionStateObserver* const observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedUserSessionStateObserver);
+};
+
 }  // namespace user_manager
 
 #endif  // COMPONENTS_USER_MANAGER_USER_MANAGER_H_