[Sync] Move sync/{internal_api,syncable} into syncer namespace

sync/syncable/read_transaction.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/syncable/read_transaction.h"
 
+namespace syncer {
 namespace syncable {
 
 ReadTransaction::ReadTransaction(const tracked_objects::Location& location,
                                  Directory* directory)
     : BaseTransaction(location, "ReadTransaction", INVALID, directory) {
   Lock();
 }
 
 ReadTransaction::~ReadTransaction() {
   HandleUnrecoverableErrorIfSet();
   Unlock();
 }
 
-} // namespace syncable
+}  // namespace syncable
+}  // namespace syncer