[Sync] Avoid unregistering object IDs on shutdown

sync/notifier/sync_notifier_helper.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_SYNC_NOTIFIER_HELPER_H_
-#define SYNC_NOTIFIER_SYNC_NOTIFIER_HELPER_H_
-
-#include <map>
-
-#include "base/basictypes.h"
-#include "base/observer_list.h"
-#include "sync/notifier/invalidation_util.h"
-#include "sync/notifier/object_id_payload_map.h"
-#include "sync/notifier/sync_notifier_observer.h"
-
-namespace syncer {
-
-// A helper class for classes that want to implement the SyncNotifier interface.
-// It helps keep track of registered handlers and which object ID registrations
-// are associated with which handlers, so implementors can just reuse the logic
-// here to dispatch invalidations and other interesting notifications.
-class SyncNotifierHelper {
- public:
-  SyncNotifierHelper();
-  ~SyncNotifierHelper();
-
-  // Updates the set of ObjectIds associated with a given |handler|. Passing an
-  // empty ObjectIdSet will unregister |handler|. The return value is an
-  // ObjectIdSet containing values for all existing handlers.
-  ObjectIdSet UpdateRegisteredIds(SyncNotifierObserver* handler,
-                                  const ObjectIdSet& ids);
-
-  // Helper that sorts incoming invalidations into a bucket for each handler
-  // and then dispatches the batched invalidations to the corresponding handler.
-  void DispatchInvalidationsToHandlers(const ObjectIdPayloadMap& id_payloads,
-                                       IncomingNotificationSource source);
-
-  // Calls the given handler method for each handler that has registered IDs.
-  void EmitOnNotificationsEnabled();
-  void EmitOnNotificationsDisabled(NotificationsDisabledReason reason);
-
- private:
-  typedef std::map<invalidation::ObjectId,
-                   SyncNotifierObserver*,
-                   ObjectIdLessThan> ObjectIdHandlerMap;
-
-  ObserverList<SyncNotifierObserver> handlers_;
-  ObjectIdHandlerMap id_to_handler_map_;
-
-  DISALLOW_COPY_AND_ASSIGN(SyncNotifierHelper);
-};
-
-}  // namespace syncer
-
-#endif  // SYNC_NOTIFIER_SYNC_NOTIFIER_HELPER_H_