[Sync] Rework Invalidator-related unit tests

sync/notifier/notifications_disabled_reason.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 SYNC_NOTIFIER_NOTIFICATIONS_DISABLED_REASON_H_
 #define SYNC_NOTIFIER_NOTIFICATIONS_DISABLED_REASON_H_
 
 #include "jingle/notifier/listener/push_client_observer.h"
 
 namespace syncer {
 
 enum NotificationsDisabledReason {
   // There is an underlying transient problem (e.g., network- or
   // XMPP-related).
   TRANSIENT_NOTIFICATION_ERROR,
   DEFAULT_NOTIFICATION_ERROR = TRANSIENT_NOTIFICATION_ERROR,
   // Our credentials have been rejected.
   NOTIFICATION_CREDENTIALS_REJECTED,
   // No error (useful as a default value or to avoid keeping a
   // separate bool for notifications enabled/disabled).
   NO_NOTIFICATION_ERROR
 };
 
 const char* NotificationsDisabledReasonToString(
     NotificationsDisabledReason reason);
 
 NotificationsDisabledReason FromNotifierReason(
     notifier::NotificationsDisabledReason reason);
 
+notifier::NotificationsDisabledReason ToNotifierReasonForTest(
+    NotificationsDisabledReason reason);
+
 }  // namespace syncer
 
 #endif  // SYNC_NOTIFIER_NOTIFICATIONS_DISABLED_REASON_H_