Refactor sync-specific parts out of SyncNotifier/SyncNotifierObserver

sync/notifier/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.
 //
 // Interface to the sync notifier, which is an object that receives
 // notifications when updates are available for a set of sync types.
 // All the observers are notified when such an event happens.
 
 #ifndef SYNC_NOTIFIER_SYNC_NOTIFIER_H_
 #define SYNC_NOTIFIER_SYNC_NOTIFIER_H_
 
 #include <string>
 
 #include "sync/internal_api/public/base/model_type.h"
 
 namespace syncer {
 class SyncNotifierObserver;
 
 class SyncNotifier {
  public:
   SyncNotifier() {}
   virtual ~SyncNotifier() {}
 
-  virtual void AddObserver(SyncNotifierObserver* observer) = 0;
-  virtual void RemoveObserver(SyncNotifierObserver* observer) = 0;
+  virtual void AddHandler(SyncNotifierObserver* observer) = 0;
+  virtual void RemoveHandler(SyncNotifierObserver* observer) = 0;
+  virtual void ReloadHandlers() = 0;

[akalin, 2012/07/11 00:10:24]

I know ReloadHandlers was in my design doc.  It was to batch registrations to
tango, but Daniel added a comment saying that we shouldn't have to worry about
it, since registrations are batched anyway.  So now I'm not sure if I still like
it.

We could have something like just:

virtual void AddHandler(ObjectId, Observer*);
virtual void RemoveHandler(ObjectId, Observer*);

instead.  Or maybe with set<ObjectId> instead.  Or map<ObjectId, Observer*>. 
What do you think?

[dcheng, 2012/07/11 05:45:28]

Add/Remove would push some of the diffing logic to each of the handlers, which I
think would be cleaner to avoid. I'll see what I can hack together for something
like SyncNotifier::UpdateHandledIds(Observer*, ObjectIdSet) though.

 
   // SetUniqueId must be called once, before any call to
   // UpdateCredentials.  |unique_id| should be a non-empty globally
   // unique string.
   virtual void SetUniqueId(const std::string& unique_id) = 0;
 
   // SetState must be called once, before any call to
   // UpdateCredentials.  |state| may be empty.
   // Deprecated in favour of InvalidationStateTracker persistence.
   virtual void SetStateDeprecated(const std::string& state) = 0;
 
   // The observers won't be notified of any notifications until
   // UpdateCredentials is called at least once. It can be called more than
   // once.
   virtual void UpdateCredentials(
       const std::string& email, const std::string& token) = 0;
 
-  virtual void UpdateEnabledTypes(syncer::ModelTypeSet enabled_types) = 0;
-
   // This is here only to support the old p2p notification implementation,
   // which is still used by sync integration tests.
   // TODO(akalin): Remove this once we move the integration tests off p2p
   // notifications.
   virtual void SendNotification(syncer::ModelTypeSet changed_types) = 0;
 };
 }  // namespace syncer
 
 #endif  // SYNC_NOTIFIER_SYNC_NOTIFIER_H_