Enable Null Syncable ID which is different than Root ID.

sync/internal_api/sync_rollback_manager_base.cc

 // Copyright 2014 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/internal_api/sync_rollback_manager_base.h"
 
 #include "sync/internal_api/public/base/model_type.h"
 #include "sync/internal_api/public/read_node.h"
 #include "sync/internal_api/public/read_transaction.h"
 #include "sync/internal_api/public/write_transaction.h"
@@ skipping 252 matching lines @@
   if (BaseNode::INIT_OK == root.InitTypeRoot(type))
     return true;
 
   syncable::MutableEntry entry(trans.GetWrappedWriteTrans(),
                                syncable::CREATE_NEW_UPDATE_ITEM,
                                syncable::Id::CreateFromServerId(
                                    ModelTypeToString(type)));
   if (!entry.good())
     return false;
 
-  entry.PutParentId(syncable::Id());
+  entry.PutParentId(syncable::Id::GetRoot());
   entry.PutBaseVersion(1);
   entry.PutUniqueServerTag(ModelTypeToRootTag(type));
   entry.PutNonUniqueName(ModelTypeToString(type));
   entry.PutIsDel(false);
   entry.PutIsDir(true);
 
   sync_pb::EntitySpecifics specifics;
   AddDefaultFieldValue(type, &specifics);
   entry.PutSpecifics(specifics);
 
@@ skipping 35 matching lines @@
 
 void SyncRollbackManagerBase::UnregisterDirectoryTypeDebugInfoObserver(
     syncer::TypeDebugInfoObserver* observer) {}
 
 bool SyncRollbackManagerBase::HasDirectoryTypeDebugInfoObserver(
     syncer::TypeDebugInfoObserver* observer) { return false; }
 
 void SyncRollbackManagerBase::RequestEmitDebugInfo() {}
 
 }  // namespace syncer