[Sync] Enable adding notifier observers from ProfileSyncService

sync/internal_api/public/sync_manager.h

Index: sync/internal_api/public/sync_manager.h
diff --git a/sync/internal_api/public/sync_manager.h b/sync/internal_api/public/sync_manager.h
index 2cbbd5c8551ded2e7ac8dfc8d1f84363995e1faa..5890173fe057585832dc7ee580542fe1de571f29 100644
--- a/sync/internal_api/public/sync_manager.h
+++ b/sync/internal_api/public/sync_manager.h
@@ -22,36 +22,31 @@
 #include "sync/internal_api/public/engine/sync_status.h"
 #include "sync/internal_api/public/util/report_unrecoverable_error_function.h"
 #include "sync/internal_api/public/util/weak_handle.h"
+#include "sync/notifier/invalidation_util.h"
 #include "sync/protocol/sync_protocol_error.h"
 
+namespace sync_pb {
+class EncryptedData;
+}  // namespace sync_pb
+
 namespace syncer {
+class BaseTransaction;
 class Encryptor;
 struct Experiments;
 class ExtensionsActivityMonitor;
+class HttpPostProviderFactory;
 class InternalComponentsFactory;
 class JsBackend;
 class JsEventHandler;
+class SyncNotifier;
+class SyncNotifierObserver;
 class SyncScheduler;
 class UnrecoverableErrorHandler;
+struct UserShare;
 
 namespace sessions {
 class SyncSessionSnapshot;
 }  // namespace sessions
-}  // namespace syncer
-
-namespace syncer {
-class SyncNotifier;
-}  // namespace syncer
-
-namespace sync_pb {
-class EncryptedData;
-}  // namespace sync_pb
-
-namespace syncer {
-
-class BaseTransaction;
-class HttpPostProviderFactory;
-struct UserShare;
 
 // Used by SyncManager::OnConnectionStatusChange().
 enum ConnectionStatus {
@@ -405,6 +400,11 @@ class SyncManager {
   virtual void UpdateEnabledTypes(
       const ModelTypeSet& enabled_types) = 0;
 
+  // Forwards to the underlying notifier (see
+  // SyncNotifier::UpdateRegisteredIds()).
+  virtual void UpdateRegisteredIds(
+      SyncNotifierObserver* handler, const ObjectIdSet& ids) = 0;
+
   // Put the syncer in normal mode ready to perform nudges and polls.
   virtual void StartSyncingNormally(
       const ModelSafeRoutingInfo& routing_info) = 0;