[Sync] Move //sync to //components/sync.

sync/syncable/syncable_read_transaction.h

-// Copyright 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.
-
-#ifndef SYNC_SYNCABLE_SYNCABLE_READ_TRANSACTION_H_
-#define SYNC_SYNCABLE_SYNCABLE_READ_TRANSACTION_H_
-
-#include <stddef.h>
-
-#include "base/macros.h"
-#include "sync/base/sync_export.h"
-#include "sync/syncable/syncable_base_transaction.h"
-
-namespace syncer {
-class ReadTransaction;
-namespace syncable {
-
-// Locks db in constructor, unlocks in destructor.
-class SYNC_EXPORT ReadTransaction : public BaseTransaction {
- public:
-  ReadTransaction(const tracked_objects::Location& from_here,
-                  Directory* directory);
-
-  ~ReadTransaction() override;
-
- protected:  // Don't allow creation on heap, except by sync API wrapper.
-  void* operator new(size_t size) { return (::operator new)(size); }
-
- private:
-  friend class syncer::ReadTransaction;
-
-  DISALLOW_COPY_AND_ASSIGN(ReadTransaction);
-};
-
-}  // namespace syncable
-}  // namespace syncer
-
-#endif  // SYNC_SYNCABLE_SYNCABLE_READ_TRANSACTION_H_