[Sync] InvalidationService shouldn't CHECK when registering ObjectId for more than one handler

components/invalidation/invalidation_notifier.h

 // Copyright 2014 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.
 //
 // An implementation of Invalidator that wraps an invalidation
 // client.  Handles the details of connecting to XMPP and hooking it
 // up to the invalidation client.
 //
 // You probably don't want to use this directly; use
 // NonBlockingInvalidator.
@@ skipping 36 matching lines @@
       const std::string& invalidation_bootstrap_data,
       const base::WeakPtr<InvalidationStateTracker>& invalidation_state_tracker,
       scoped_refptr<base::SingleThreadTaskRunner>
           invalidation_state_tracker_task_runner,
       const std::string& client_info);
 
   ~InvalidationNotifier() override;
 
   // Invalidator implementation.
   void RegisterHandler(InvalidationHandler* handler) override;
-  void UpdateRegisteredIds(InvalidationHandler* handler,
+  bool UpdateRegisteredIds(InvalidationHandler* handler,
                            const ObjectIdSet& ids) override;
   void UnregisterHandler(InvalidationHandler* handler) override;
   InvalidatorState GetInvalidatorState() const override;
   void UpdateCredentials(const std::string& email,
                          const std::string& token) override;
   void RequestDetailedStatus(base::Callback<void(const base::DictionaryValue&)>
                                  callback) const override;
 
   // SyncInvalidationListener::Delegate implementation.
   void OnInvalidate(const ObjectIdInvalidationMap& invalidation_map) override;
@@ skipping 32 matching lines @@
 
   // The invalidation listener.
   SyncInvalidationListener invalidation_listener_;
 
   DISALLOW_COPY_AND_ASSIGN(InvalidationNotifier);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_INVALIDATION_INVALIDATION_NOTIFIER_H_