Changes to add duration into history database.

chrome/browser/history/visit_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_VISIT_DATABASE_H_
 #define CHROME_BROWSER_HISTORY_VISIT_DATABASE_H_
 #pragma once
 
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/history/history_types.h"
@@ skipping 171 matching lines @@
   bool InitVisitTable();
 
   // Convenience to fill a VisitRow. Assumes the visit values are bound starting
   // at index 0.
   static void FillVisitRow(sql::Statement& statement, VisitRow* visit);
 
   // Convenience to fill a VisitVector. Assumes that statement.step()
   // hasn't happened yet.
   static bool FillVisitVector(sql::Statement& statement, VisitVector* visits);
 
+  // Called by the derived classes to migrate the older visits table which
+  // don't have visit_duration column yet.
+  bool MigrateVisitsWithoutDuration();
+
  private:
   class VisitAnalysis;
   scoped_ptr<VisitAnalysis> visit_analysis_;
 
   DISALLOW_COPY_AND_ASSIGN(VisitDatabase);
 };
 
 }  // history
 
 #endif  // CHROME_BROWSER_HISTORY_VISIT_DATABASE_H_