ash: Use enum for SessionController::CycleActiveUser

ash/public/cpp/session_types.h

Index: ash/public/cpp/session_types.h
diff --git a/ash/public/cpp/session_types.h b/ash/public/cpp/session_types.h
index c5c59f031e36e3a5bdb5d2e8a3b2f9c93e56c1a8..74734807c8319f89a70f4631aac28f1ce7f40d89 100644
--- a/ash/public/cpp/session_types.h
+++ b/ash/public/cpp/session_types.h
@@ -23,6 +23,12 @@ enum class AddUserSessionPolicy {
   ERROR_MAXIMUM_USERS_REACHED,
 };
 
+// Defines the cycle direction for |CycleActiveUser|.
+enum class CycleUserDirection {
+  NEXT = 0,  // Cycle to the next user.
+  PREVIOUS,  // Cycle to the previous user.
+};
+
 }  // namespace ash
 
 #endif  // ASH_PUBLIC_CPP_SESSION_TYPES_H_