[Sync] Avoid unregistering object IDs on shutdown

chrome/browser/sync/glue/bridged_sync_notifier.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_BRIDGED_SYNC_NOTIFIER_H_
 #define CHROME_BROWSER_SYNC_GLUE_BRIDGED_SYNC_NOTIFIER_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "sync/notifier/sync_notifier.h"
@@ skipping 11 matching lines @@
 class BridgedSyncNotifier : public syncer::SyncNotifier {
  public:
   // Does not take ownership of |bridge|. Takes ownership of |delegate|.
   // |delegate| may be NULL.
   BridgedSyncNotifier(ChromeSyncNotificationBridge* bridge,
                       syncer::SyncNotifier* delegate);
   virtual ~BridgedSyncNotifier();
 
   // SyncNotifier implementation. Passes through all calls to the delegate.
   // UpdateRegisteredIds calls will also be forwarded to the bridge.
-  virtual void UpdateRegisteredIds(syncer::SyncNotifierObserver* handler,
+  virtual void SetHandler(const std::string& handler_name,

[msw, 2012/08/07 20:09:30]

When a Handler wants to unregister itself in this paradigm, it'll call
SetHandler("Foo", NULL), but what if another handler has taken over "Foo"? Using
strings seems easily vulnerable to unintended actions like unregistering another
handler when you try to unregister yourself.

What's the reasoning behind this approach and are you concerned about this extra
level of complication/indirection?

+                          syncer::SyncNotifierObserver* handler) OVERRIDE;
+  virtual void UpdateRegisteredIds(const std::string& handler_name,
                                    const syncer::ObjectIdSet& ids) OVERRIDE;
   virtual void SetUniqueId(const std::string& unique_id) OVERRIDE;
   virtual void SetStateDeprecated(const std::string& state) OVERRIDE;
   virtual void UpdateCredentials(
       const std::string& email, const std::string& token) OVERRIDE;
   virtual void SendNotification(
       syncer::ModelTypeSet changed_types) OVERRIDE;
 
  private:
   // The notification bridge that we register the observers with.
   ChromeSyncNotificationBridge* bridge_;
 
   // The delegate we are wrapping.
   scoped_ptr<syncer::SyncNotifier> delegate_;
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_GLUE_BRIDGED_SYNC_NOTIFIER_H_