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

components/invalidation/fake_invalidator.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.
 
 #ifndef COMPONENTS_INVALIDATION_FAKE_INVALIDATOR_H_
 #define COMPONENTS_INVALIDATION_FAKE_INVALIDATOR_H_
 
 #include <string>
 
 #include "base/callback_forward.h"
@@ skipping 13 matching lines @@
   ObjectIdSet GetRegisteredIds(InvalidationHandler* handler) const;
   const std::string& GetUniqueId() const;
   const std::string& GetCredentialsEmail() const;
   const std::string& GetCredentialsToken() const;
 
   void EmitOnInvalidatorStateChange(InvalidatorState state);
   void EmitOnIncomingInvalidation(
       const ObjectIdInvalidationMap& invalidation_map);
 
   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;
 
  private:
   InvalidatorRegistrar registrar_;
   std::string state_;
   std::string email_;
   std::string token_;
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_INVALIDATION_FAKE_INVALIDATOR_H_