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

sync/notifier/non_blocking_invalidation_notifier.h

Index: sync/notifier/non_blocking_invalidation_notifier.h
===================================================================
--- sync/notifier/non_blocking_invalidation_notifier.h	(revision 150991)
+++ sync/notifier/non_blocking_invalidation_notifier.h	(working copy)
@@ -18,8 +18,8 @@
 #include "sync/internal_api/public/util/weak_handle.h"
 #include "sync/notifier/invalidation_state_tracker.h"
 #include "sync/notifier/sync_notifier.h"
+#include "sync/notifier/sync_notifier_helper.h"
 #include "sync/notifier/sync_notifier_observer.h"
-#include "sync/notifier/sync_notifier_registrar.h"
 
 namespace base {
 class SingleThreadTaskRunner;
@@ -27,8 +27,6 @@
 
 namespace syncer {
 
-// TODO(akalin): Generalize to NonBlockingSyncNotifier
-// (http://crbug.com/140409).
 class NonBlockingInvalidationNotifier
     : public SyncNotifier,
       // SyncNotifierObserver to "observe" our Core via WeakHandle.
@@ -46,10 +44,8 @@
   virtual ~NonBlockingInvalidationNotifier();
 
   // SyncNotifier implementation.
-  virtual void RegisterHandler(SyncNotifierObserver* handler) OVERRIDE;
   virtual void UpdateRegisteredIds(SyncNotifierObserver* handler,
                                    const ObjectIdSet& ids) OVERRIDE;
-  virtual void UnregisterHandler(SyncNotifierObserver* handler) OVERRIDE;
   virtual void SetUniqueId(const std::string& unique_id) OVERRIDE;
   virtual void SetStateDeprecated(const std::string& state) OVERRIDE;
   virtual void UpdateCredentials(
@@ -69,7 +65,7 @@
 
   base::WeakPtrFactory<NonBlockingInvalidationNotifier> weak_ptr_factory_;
 
-  SyncNotifierRegistrar registrar_;
+  SyncNotifierHelper helper_;
 
   // The real guts of NonBlockingInvalidationNotifier, which allows
   // this class to live completely on the parent thread.