Create meta table atomically.

chrome/browser/history/download_database.h

 // 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.
 
 #ifndef CHROME_BROWSER_HISTORY_DOWNLOAD_DATABASE_H_
 #define CHROME_BROWSER_HISTORY_DOWNLOAD_DATABASE_H_
 #pragma once
 
 #include <set>
 #include <string>
@@ skipping 46 matching lines @@
   // Remove all completed downloads that started after |remove_begin|
   // (inclusive) and before |remove_end|. You may use null Time values
   // to do an unbounded delete in either direction. This function ignores
   // all downloads that are in progress or are waiting to be cancelled.
   bool RemoveDownloadsBetween(base::Time remove_begin, base::Time remove_end);
 
  protected:
   // Returns the database for the functions in this interface.
   virtual sql::Connection& GetDB() = 0;
 
+  // Returns the meta-table object for the functions in this interface.
+  virtual sql::MetaTable& GetMetaTable() = 0;
+
   // Creates the downloads table if needed.
   bool InitDownloadTable();
 
   // Used to quickly clear the downloads. First you would drop it, then you
   // would re-initialize it.
   bool DropDownloadTable();
 
  private:
   // TODO(rdsmith): Remove after http://crbug.com/96627 has been resolved.
   void CheckThread();
 
   bool EnsureColumnExists(const std::string& name, const std::string& type);
 
   bool owning_thread_set_;
   base::PlatformThreadId owning_thread_;
 
   int next_id_;
   int next_db_handle_;
-  sql::MetaTable meta_table_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadDatabase);
 };
 
 }  // namespace history
 
 #endif  // CHROME_BROWSER_HISTORY_DOWNLOAD_DATABASE_H_