ash: Use enum for SessionController::CycleActiveUser

ash/public/interfaces/session_controller.mojom

Index: ash/public/interfaces/session_controller.mojom
diff --git a/ash/public/interfaces/session_controller.mojom b/ash/public/interfaces/session_controller.mojom
index aea9449dd3db34a209f3d59761a70e5eed58dafe..9531590e0a17b6a256df9f9009373f7345f317f2 100644
--- a/ash/public/interfaces/session_controller.mojom
+++ b/ash/public/interfaces/session_controller.mojom
@@ -65,6 +65,12 @@ enum UserType {
   ACTIVE_DIRECTORY,
 };
 
+// Matches ash::CycleUserDirection.
+enum CycleUserDirection {
+  NEXT,  // Cycle to the next user.
+  PREVIOUS,  // Cycle to the previous user.
+};
+
 // Info about a user session in ash.
 struct UserSession {
   // A user session id for the user session. It is generated by session manager
@@ -140,5 +146,5 @@ interface SessionControllerClient {
   SwitchActiveUser(signin.mojom.AccountId account_id);
 
   // Switch the active user to the next or previous user.
-  CycleActiveUser(bool next_user);
+  CycleActiveUser(CycleUserDirection direction);
 };