ash: Use enum for SessionController::CycleActiveUser

ash/common/session/session_controller.h

 // Copyright 2016 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 ASH_COMMON_SESSION_SESSION_CONTROLLER_H_
 #define ASH_COMMON_SESSION_SESSION_CONTROLLER_H_
 
 #include <stdint.h>
 
 #include <vector>
@@ skipping 62 matching lines @@
 
   // Locks the screen. The locking happens asynchronously.
   void LockScreen();
 
   // Switches to another active user with |account_id| (if that user has
   // already signed in).
   void SwitchActiveUser(const AccountId& account_id);
 
   // Switches the active user to the next or previous user, with the same
   // ordering as user sessions are created.
-  void CycleActiveUser(bool next_user);
+  void CycleActiveUser(CycleUserDirection direction);
 
   void AddSessionStateObserver(SessionStateObserver* observer);
   void RemoveSessionStateObserver(SessionStateObserver* observer);
 
   // mojom::SessionController
   void SetClient(mojom::SessionControllerClientPtr client) override;
   void SetSessionInfo(mojom::SessionInfoPtr info) override;
   void UpdateUserSession(mojom::UserSessionPtr user_session) override;
   void SetUserSessionOrder(
       const std::vector<uint32_t>& user_session_order) override;
@@ skipping 25 matching lines @@
   uint32_t active_session_id_ = 0u;
 
   base::ObserverList<ash::SessionStateObserver> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(SessionController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SESSION_SESSION_CONTROLLER_H_