Add the "virtual" keyword on method overrides that are missing it.

chrome/browser/history/history_backend.h

 // Copyright (c) 2010 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_HISTORY_BACKEND_H_
 #define CHROME_BROWSER_HISTORY_HISTORY_BACKEND_H_
 #pragma once
 
 #include <string>
 #include <utility>
@@ skipping 435 matching lines @@
   // Processes the next scheduled HistoryDBTask, scheduling this method
   // to be invoked again if there are more tasks that need to run.
   void ProcessDBTaskImpl();
 
   // Release all tasks in history_db_tasks_ and clears it.
   void ReleaseDBTasks();
 
   // Schedules a broadcast of the given notification on the main thread. The
   // details argument will have ownership taken by this function (it will be
   // sent to the main thread and deleted there).
-  void BroadcastNotifications(NotificationType type,
-                              HistoryDetails* details_deleted);
+  virtual void BroadcastNotifications(NotificationType type,
+                                      HistoryDetails* details_deleted);
 
   // Deleting all history ------------------------------------------------------
 
   // Deletes all history. This is a special case of deleting that is separated
   // from our normal dependency-following method for performance reasons. The
   // logic lives here instead of ExpireHistoryBackend since it will cause
   // re-initialization of some databases such as Thumbnails or Archived that
   // could fail. When these databases are not valid, our pointers must be NULL,
   // so we need to handle this type of operation to keep the pointers in sync.
   void DeleteAllHistory();
@@ skipping 101 matching lines @@
   // Publishes the history to all indexers which are registered to receive
   // history data from us. Can be NULL if there are no listeners.
   scoped_ptr<HistoryPublisher> history_publisher_;
 
   DISALLOW_COPY_AND_ASSIGN(HistoryBackend);
 };
 
 }  // namespace history
 
 #endif  // CHROME_BROWSER_HISTORY_HISTORY_BACKEND_H_