[Sync] Avoid unregistering object IDs on shutdown

chrome/browser/sync/profile_sync_service.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_PROFILE_SYNC_SERVICE_H_
 #define CHROME_BROWSER_SYNC_PROFILE_SYNC_SERVICE_H_
 
 #include <list>
 #include <string>
 
@@ skipping 534 matching lines @@
     return configure_status_;
   }
 
   // If true, the ProfileSyncService has detected that a new GAIA signin has
   // succeeded, and is waiting for initialization to complete. This is used by
   // the UI to differentiate between a new auth error (encountered as part of
   // the initialization process) and a pre-existing auth error that just hasn't
   // been cleared yet. Virtual for testing purposes.
   virtual bool waiting_for_auth() const;
 
-  // Updates the set of ObjectIds associated with a given |handler|.
-  // Passing an empty ObjectIdSet will unregister |handler|.
-  // There should be at most one handler registered per object id.
+  // NOTE(akalin): Invalidations that come in during browser shutdown may get
+  // dropped.  This won't matter once we have an Acknowledge API, though: see
+  // http://crbug.com/78462 and http://crbug.com/124149.
+
+  // Sets the invalidation handler for the given name.  Pass in NULL for
+  // |handler| if you want to remove the handler for the given name.  (This
+  // doesn't unregister the IDs for the given name, though.)  A handler must be
+  // set for at most one name.
   //
-  // The handler -> registered ids map is persisted across restarts of
+  // The handler name -> handler map is persisted across restarts of sync.
+  void SetInvalidationHandler(const std::string& handler_name,

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

I'm wondering if using strings is a necessity to avoiding unregistering object
ids on shutdown. Wouldn't it make more sense to just add something like
InvalidationHandlerDestroying(syncer::SyncNotifierObserver* handler) called from
SyncNotifierObserver::~SyncNotifierObserver (or some new
SyncNotifierObserver::Disable/ShutDown function) that would disable the handler
without unregistering its ids?

That would seem to avoid your dangling object IDs concern, avoid the
string->handler map, and simplify client-side logic on destruction.

+                              syncer::SyncNotifierObserver* handler);
+
+  // Updates the set of ObjectIds associated with a given invalidation handler
+  // (via its name). An ID must be registered for at most one handler.
+  //
+  // The handler name -> registered ids map is persisted across restarts of
   // sync.
-  void UpdateRegisteredInvalidationIds(syncer::SyncNotifierObserver* handler,
+  void UpdateRegisteredInvalidationIds(const std::string& handler_name,
                                        const syncer::ObjectIdSet& ids);
 
   // ProfileKeyedService implementation.
   virtual void Shutdown() OVERRIDE;
 
  protected:
   // Used by test classes that derive from ProfileSyncService.
   virtual browser_sync::SyncBackendHost* GetBackendForTest();
 
   // Helper to install and configure a data type manager.
@@ skipping 256 matching lines @@
   // If |true|, there is setup UI visible so we should not start downloading
   // data types.
   bool setup_in_progress_;
 
   // The set of currently enabled sync experiments.
   syncer::Experiments current_experiments;
 
   // Factory the backend will use to build the SyncManager.
   syncer::SyncManagerFactory sync_manager_factory_;
 
-  // The set of all registered IDs.
-  syncer::ObjectIdSet all_registered_ids_;
-
   // Dispatches invalidations to handlers.
   syncer::SyncNotifierHelper notifier_helper_;
 
   DISALLOW_COPY_AND_ASSIGN(ProfileSyncService);
 };
 
 bool ShouldShowActionOnUI(
     const syncer::SyncProtocolError& error);
 
 
 #endif  // CHROME_BROWSER_SYNC_PROFILE_SYNC_SERVICE_H_