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

chrome/browser/download/download_request_limiter.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_DOWNLOAD_DOWNLOAD_REQUEST_LIMITER_H_
 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_REQUEST_LIMITER_H_
 #pragma once
 
 #include <map>
 #include <string>
@@ skipping 113 matching lines @@
     TabDownloadState()
         : host_(NULL),
           controller_(NULL),
           status_(DownloadRequestLimiter::ALLOW_ONE_DOWNLOAD),
           download_count_(0),
           infobar_(NULL) {
     }
 
    private:
     // NotificationObserver method.
-    void Observe(NotificationType type,
-                 const NotificationSource& source,
-                 const NotificationDetails& details);
+    virtual void Observe(NotificationType type,
+                         const NotificationSource& source,
+                         const NotificationDetails& details);
 
     // Notifies the callbacks as to whether the download is allowed or not.
     // Updates status_ appropriately.
     void NotifyCallbacks(bool allow);
 
     DownloadRequestLimiter* host_;
 
     NavigationController* controller_;
 
     // Host of the first page the download started on. This may be empty.
@@ skipping 96 matching lines @@
   // the TabDownloadState is removed and deleted (by way of Remove).
   typedef std::map<NavigationController*, TabDownloadState*> StateMap;
   StateMap state_map_;
 
   static TestingDelegate* delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadRequestLimiter);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_REQUEST_LIMITER_H_