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

chrome/browser/sessions/session_service.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_SESSIONS_SESSION_SERVICE_H_
 #define CHROME_BROWSER_SESSIONS_SESSION_SERVICE_H_
 #pragma once
 
 #include <map>
 #include <string>
@@ skipping 329 matching lines @@
   // from the state of the browser.
   void ScheduleReset();
 
   // Searches for a pending command that can be replaced with command.
   // If one is found, pending command is removed, command is added to
   // the pending commands and true is returned.
   bool ReplacePendingCommand(SessionCommand* command);
 
   // Schedules the specified command. This method takes ownership of the
   // command.
-  void ScheduleCommand(SessionCommand* command);
+  virtual void ScheduleCommand(SessionCommand* command);
 
   // Converts all pending tab/window closes to commands and schedules them.
   void CommitPendingCloses();
 
   // Returns true if there is only one window open with a single tab that shares
   // our profile.
   bool IsOnlyOneTabLeft();
 
   // Returns true if there are open trackable browser windows whose ids do
   // match |window_id| with our profile. A trackable window is a window from
@@ skipping 91 matching lines @@
 
   // Constants used in calculating histogram data.
   const base::TimeDelta save_delay_in_millis_;
   const base::TimeDelta save_delay_in_mins_;
   const base::TimeDelta save_delay_in_hrs_;
 
   DISALLOW_COPY_AND_ASSIGN(SessionService);
 };
 
 #endif  // CHROME_BROWSER_SESSIONS_SESSION_SERVICE_H_