Original patch by rlarocque@chromium.org at http://codereview.chromium.org/7633077/

chrome/browser/sync/internal_api/read_transaction.h

+// Copyright (c) 2011 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 CHROME_BROWSER_SYNC_INTERNAL_API_READ_TRANSACTION_H_
+#define CHROME_BROWSER_SYNC_INTERNAL_API_READ_TRANSACTION_H_
+
+#include "chrome/browser/sync/internal_api/base_transaction.h"
+
+namespace tracked_objects {
+class Location;
+}  // namespace tracked_objects
+
+namespace sync_api {
+
+struct UserShare;
+
+// Sync API's ReadTransaction is a read-only BaseTransaction.  It wraps
+// a syncable::ReadTransaction.
+class ReadTransaction : public BaseTransaction {
+ public:
+  // Start a new read-only transaction on the specified repository.
+  ReadTransaction(const tracked_objects::Location& from_here,
+                  UserShare* share);
+
+  // Resume the middle of a transaction. Will not close transaction.
+  ReadTransaction(UserShare* share, syncable::BaseTransaction* trans);
+
+  virtual ~ReadTransaction();
+
+  // BaseTransaction override.
+  virtual syncable::BaseTransaction* GetWrappedTrans() const;
+ private:
+  void* operator new(size_t size);  // Transaction is meant for stack use only.
+
+  // The underlying syncable object which this class wraps.
+  syncable::BaseTransaction* transaction_;
+  bool close_transaction_;
+
+  DISALLOW_COPY_AND_ASSIGN(ReadTransaction);
+};
+
+} // namespace sync_api
+
+#endif  // CHROME_BROWSER_SYNC_INTERNAL_API_READ_TRANSACTION_H_