[USS] Change the place where SharedModelTypeProcessor got created

sync/api/model_type_service.cc

Index: sync/api/model_type_service.cc
diff --git a/sync/api/model_type_service.cc b/sync/api/model_type_service.cc
index 87df14bf6011dc559b98e90082d0e2d29f1235d7..a61488c92863747ed1540623b41722cd781ac6d1 100644
--- a/sync/api/model_type_service.cc
+++ b/sync/api/model_type_service.cc
@@ -14,11 +14,13 @@ 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() {