Refactor sync-specific parts out of SyncNotifier/SyncNotifierObserver

sync/notifier/sync_notifier.h

Index: sync/notifier/sync_notifier.h
diff --git a/sync/notifier/sync_notifier.h b/sync/notifier/sync_notifier.h
index 24c59a018c4f8126ef6a7f0457cae941a6597a47..3a57270eaa2bda1c7862aede26005acf66bb84e0 100644
--- a/sync/notifier/sync_notifier.h
+++ b/sync/notifier/sync_notifier.h
@@ -12,6 +12,7 @@
 #include <string>
 
 #include "sync/internal_api/public/base/model_type.h"
+#include "sync/notifier/invalidation_util.h"
 
 namespace syncer {
 class SyncNotifierObserver;
@@ -21,8 +22,8 @@ class SyncNotifier {
   SyncNotifier() {}
   virtual ~SyncNotifier() {}
 
-  virtual void AddObserver(SyncNotifierObserver* observer) = 0;
-  virtual void RemoveObserver(SyncNotifierObserver* observer) = 0;
+  virtual void UpdateRegisteredIds(SyncNotifierObserver* handler,
+                                   const ObjectIdSet& ids) = 0;
 
   // SetUniqueId must be called once, before any call to
   // UpdateCredentials.  |unique_id| should be a non-empty globally
@@ -40,8 +41,6 @@ class SyncNotifier {
   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