[Sync] Avoid unregistering object IDs on shutdown

chrome/browser/sync/glue/chrome_sync_notification_bridge.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 CHROME_BROWSER_SYNC_GLUE_CHROME_SYNC_NOTIFICATION_BRIDGE_H_
 #define CHROME_BROWSER_SYNC_GLUE_CHROME_SYNC_NOTIFICATION_BRIDGE_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "base/sequenced_task_runner.h"
@@ skipping 18 matching lines @@
 // each observer's OnIncomingNotification method on these
 // notifications (on the sync task runner).
 class ChromeSyncNotificationBridge : public content::NotificationObserver {
  public:
   // Must be created and destroyed on the UI thread.
   ChromeSyncNotificationBridge(
       const Profile* profile,
       const scoped_refptr<base::SequencedTaskRunner>& sync_task_runner);
   virtual ~ChromeSyncNotificationBridge();
 
+  // Must be called on the UI thread while the sync task runner is still
+  // around.  No other member functions on the sync thread may be called after
+  // this is called.
+  void StopForShutdown();
+
   // Must be called on the sync task runner.
   void UpdateEnabledTypes(syncer::ModelTypeSet enabled_types);
   // Marked virtual for tests.
+  virtual void RegisterHandler(syncer::SyncNotifierObserver* handler);
   virtual void UpdateRegisteredIds(syncer::SyncNotifierObserver* handler,
                                    const syncer::ObjectIdSet& ids);
+  virtual void UnregisterHandler(syncer::SyncNotifierObserver* handler);
 
   // NotificationObserver implementation. Called on UI thread.
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
  private:
   // Inner class to hold all the bits used on |sync_task_runner_|.
   class Core;
 
   const scoped_refptr<base::SequencedTaskRunner> sync_task_runner_;
 
   // Created on the UI thread, used only on |sync_task_runner_|.
   const scoped_refptr<Core> core_;
 
   // Used only on the UI thread.
   content::NotificationRegistrar registrar_;
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_GLUE_CHROME_SYNC_NOTIFICATION_BRIDGE_H_