[Sync] Avoid unregistering object IDs on shutdown

sync/internal_api/public/sync_manager.h

Index: sync/internal_api/public/sync_manager.h
diff --git a/sync/internal_api/public/sync_manager.h b/sync/internal_api/public/sync_manager.h
index 0cb6a4c26dd3c1645f07b94262b5cd607ce0e92c..01d919c16c2260cc31cc068ad1bd14ef2457963c 100644
--- a/sync/internal_api/public/sync_manager.h
+++ b/sync/internal_api/public/sync_manager.h
@@ -407,12 +407,19 @@ class SyncManager {
   virtual void UpdateEnabledTypes(
       const ModelTypeSet& enabled_types) = 0;
 
-  // Forwards to the underlying notifier (see
-  // SyncNotifier::UpdateRegisteredIds()).
+  // 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).
   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;