sync: Support non-blocking initial sync in proto

sync/engine/sync_scheduler_impl.h

 // Copyright 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 SYNC_ENGINE_SYNC_SCHEDULER_IMPL_H_
 #define SYNC_ENGINE_SYNC_SCHEDULER_IMPL_H_
 
 #include <map>
 #include <string>
 
@@ skipping 50 matching lines @@
       const tracked_objects::Location& nudge_location) OVERRIDE;
   virtual void ScheduleLocalRefreshRequest(
       const base::TimeDelta& desired_delay,
       ModelTypeSet types,
       const tracked_objects::Location& nudge_location) OVERRIDE;
   virtual void ScheduleInvalidationNudge(
       const base::TimeDelta& desired_delay,
       syncer::ModelType type,
       scoped_ptr<InvalidationInterface> invalidation,
       const tracked_objects::Location& nudge_location) OVERRIDE;
+  virtual void ScheduleInitialSyncNudge(syncer::ModelType model_type) OVERRIDE;
   virtual void SetNotificationsEnabled(bool notifications_enabled) OVERRIDE;
 
   virtual base::TimeDelta GetSessionsCommitDelay() const OVERRIDE;
 
   virtual void OnCredentialsUpdated() OVERRIDE;
   virtual void OnConnectionStatusChange() OVERRIDE;
 
   // SyncSession::Delegate implementation.
   virtual void OnThrottled(const base::TimeDelta& throttle_duration) OVERRIDE;
   virtual void OnTypesThrottled(
@@ skipping 247 matching lines @@
   // A second factory specially for weak_handle_this_, to allow the handle
   // to be const and alleviate threading concerns.
   base::WeakPtrFactory<SyncSchedulerImpl> weak_ptr_factory_for_weak_handle_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncSchedulerImpl);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_ENGINE_SYNC_SCHEDULER_IMPL_H_