[USS] Change the place where SharedModelTypeProcessor got created

sync/api/model_type_service.cc

 // Copyright 2015 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.
 
 #include "sync/api/model_type_service.h"
 
 namespace syncer_v2 {
 
 ModelTypeService::ModelTypeService() {}
 
 ModelTypeService::~ModelTypeService() {}
 
 ModelTypeChangeProcessor* ModelTypeService::change_processor() const {
   return change_processor_.get();
 }
 
-void ModelTypeService::set_change_processor(
-    scoped_ptr<ModelTypeChangeProcessor> change_processor) {
-  DCHECK(!change_processor_);
-  change_processor_.swap(change_processor);
+ModelTypeChangeProcessor* ModelTypeService::InitializeProcessor(
+    const SharedProcessorFactory& shared_processor_factory) {
+  DCHECK(!change_processor_.get());
+  change_processor_.reset(shared_processor_factory.Run(this).release());
   OnChangeProcessorSet();
+
+  return change_processor_.get();
 }
 
 void ModelTypeService::clear_change_processor() {
   change_processor_.reset();
 }
 
 }  // namespace syncer_v2