[Sync] Convert DTCs to be not RefCounted and NonThreadSafe.

components/sync/api/model_type_service.cc

Index: components/sync/api/model_type_service.cc
diff --git a/components/sync/api/model_type_service.cc b/components/sync/api/model_type_service.cc
index ea2eedefc7f3ce019e81ac7654c291172ced1599..59ed6ff266c8b8a7369b6121ca011a22f2222e20 100644
--- a/components/sync/api/model_type_service.cc
+++ b/components/sync/api/model_type_service.cc
@@ -4,8 +4,10 @@
 
 #include "components/sync/api/model_type_service.h"
 
+#include <utility>
+
+#include "components/sync/api/data_type_error_handler.h"
 #include "components/sync/api/model_type_change_processor.h"
-#include "components/sync/core/data_type_error_handler.h"
 
 namespace syncer_v2 {
 
@@ -28,10 +30,10 @@ ConflictResolution ModelTypeService::ResolveConflict(
 }
 
 void ModelTypeService::OnSyncStarting(
-    syncer::DataTypeErrorHandler* error_handler,
+    std::unique_ptr<syncer::DataTypeErrorHandler> error_handler,
     const ModelTypeChangeProcessor::StartCallback& start_callback) {
   CreateChangeProcessor();
-  change_processor_->OnSyncStarting(error_handler, start_callback);
+  change_processor_->OnSyncStarting(std::move(error_handler), start_callback);
 }
 
 void ModelTypeService::DisableSync() {