Revert 150990 - [Sync] Avoid unregistering object IDs on shutdown

sync/internal_api/public/sync_manager.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_INTERNAL_API_PUBLIC_SYNC_MANAGER_H_
 #define SYNC_INTERNAL_API_PUBLIC_SYNC_MANAGER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 389 matching lines @@
   // Returns false if an error occurred, true otherwise.
   virtual bool PurgePartiallySyncedTypes() = 0;
 
   // Update tokens that we're using in Sync. Email must stay the same.
   virtual void UpdateCredentials(const SyncCredentials& credentials) = 0;
 
   // Called when the user disables or enables a sync type.
   virtual void UpdateEnabledTypes(
       const ModelTypeSet& enabled_types) = 0;
 
-  // Forwards to the underlying notifier (see comments in sync_notifier.h).
-  virtual void RegisterInvalidationHandler(
-      SyncNotifierObserver* handler) = 0;
-
-  // Forwards to the underlying notifier (see comments in sync_notifier.h).
+  // Forwards to the underlying notifier (see
+  // SyncNotifier::UpdateRegisteredIds()).
   virtual void UpdateRegisteredInvalidationIds(
       SyncNotifierObserver* handler,
       const ObjectIdSet& ids) = 0;
 
-  // Forwards to the underlying notifier (see comments in sync_notifier.h).
-  virtual void UnregisterInvalidationHandler(
-      SyncNotifierObserver* handler) = 0;
-
   // Put the syncer in normal mode ready to perform nudges and polls.
   virtual void StartSyncingNormally(
       const ModelSafeRoutingInfo& routing_info) = 0;
 
   // Attempts to re-encrypt encrypted data types using the passphrase provided.
   // Notifies observers of the result of the operation via OnPassphraseAccepted
   // or OnPassphraseRequired, updates the nigori node, and does re-encryption as
   // appropriate. If an explicit password has been set previously, we drop
   // subsequent requests to set a passphrase. If the cryptographer has pending
   // keys, and a new implicit passphrase is provided, we try decrypting the
@@ skipping 96 matching lines @@
   virtual bool ReceivedExperiment(Experiments* experiments) = 0;
 
   // Uses a read-only transaction to determine if the directory being synced has
   // any remaining unsynced items.  May be called on any thread.
   virtual bool HasUnsyncedItems() = 0;
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_SYNC_MANAGER_H_