Enable Null Syncable ID which is different than Root ID.

sync/internal_api/base_node.cc

 // Copyright (c) 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.
 
 #include "sync/internal_api/public/base_node.h"
 
 #include <stack>
 
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 159 matching lines @@
 }
 
 bool BaseNode::HasChildren() const {
   syncable::Directory* dir = GetTransaction()->GetDirectory();
   syncable::BaseTransaction* trans = GetTransaction()->GetWrappedTrans();
   return dir->HasChildren(trans, GetEntry()->GetId());
 }
 
 int64 BaseNode::GetPredecessorId() const {
   syncable::Id id_string = GetEntry()->GetPredecessorId();
-  if (id_string.IsRoot())
+  if (id_string.IsNull())
     return kInvalidId;
   return IdToMetahandle(GetTransaction()->GetWrappedTrans(), id_string);
 }
 
 int64 BaseNode::GetSuccessorId() const {
   syncable::Id id_string = GetEntry()->GetSuccessorId();
-  if (id_string.IsRoot())
+  if (id_string.IsNull())
     return kInvalidId;
   return IdToMetahandle(GetTransaction()->GetWrappedTrans(), id_string);
 }
 
 int64 BaseNode::GetFirstChildId() const {
   syncable::Id id_string = GetEntry()->GetFirstChildId();
-  if (id_string.IsRoot())
+  if (id_string.IsNull())
     return kInvalidId;
   return IdToMetahandle(GetTransaction()->GetWrappedTrans(), id_string);
 }
 
 void BaseNode::GetChildIds(std::vector<int64>* result) const {
   GetEntry()->GetChildHandles(result);
 }
 
 int BaseNode::GetTotalNodeCount() const {
   return GetEntry()->GetTotalNodeCount();
@@ skipping 99 matching lines @@
     const sync_pb::EntitySpecifics& specifics) {
   ModelType type = GetModelTypeFromSpecifics(specifics);
   DCHECK_NE(UNSPECIFIED, type);
   if (GetModelType() != UNSPECIFIED) {
     DCHECK_EQ(GetModelType(), type);
   }
   unencrypted_data_.CopyFrom(specifics);
 }
 
 }  // namespace syncer