Fix races in txnBuf

filter/txnBuf/ds.go

 // 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.
 
 package txnBuf
 
 import (
         "golang.org/x/net/context"
 
         ds "github.com/luci/gae/service/datastore"
 )
 
 type dsBuf struct {
         ds.RawInterface
-
-        ns string
 }
 
 var _ ds.RawInterface = (*dsBuf)(nil)
 
 func (d *dsBuf) RunInTransaction(f func(context.Context) error, opts *ds.TransactionOptions) error {
         return doRunInTransaction(d.RawInterface, f, opts)
 }
 
 func doRunInTransaction(base ds.RawInterface, f func(context.Context) error, opts *ds.TransactionOptions) error {
         return base.RunInTransaction(func(ctx context.Context) error {
                 return withTxnBuf(ctx, f, opts)
         }, opts)
 }