[Sync] Move //components/sync to the syncer namespace, take 2.

components/sync/core/data_batch_impl.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 "components/sync/core/data_batch_impl.h"
 
-namespace syncer_v2 {
+namespace syncer {
 
 DataBatchImpl::DataBatchImpl() {}
 
 DataBatchImpl::~DataBatchImpl() {}
 
 void DataBatchImpl::Put(const std::string& storage_key,
                         std::unique_ptr<EntityData> specifics) {
   key_data_pairs_.push_back(KeyAndData(storage_key, std::move(specifics)));
 }
 
 bool DataBatchImpl::HasNext() const {
   return key_data_pairs_.size() > read_index_;
 }
 
 KeyAndData DataBatchImpl::Next() {
   DCHECK(HasNext());
   return std::move(key_data_pairs_[read_index_++]);
 }
 
-}  // namespace syncer_v2
+}  // namespace syncer