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

chrome/browser/extensions/extension_browser_event_router.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_EXTENSIONS_EXTENSION_BROWSER_EVENT_ROUTER_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_BROWSER_EVENT_ROUTER_H_
 #pragma once
 
 #include <map>
 #include <string>
@@ skipping 74 matching lines @@
                           const std::string& page_action_id,
                           int tab_id,
                           const std::string& url,
                           int button);
   // Browser Actions execute event.
   void BrowserActionExecuted(Profile* profile,
                              const std::string& extension_id,
                              Browser* browser);
 
   // NotificationObserver.
-  void Observe(NotificationType type,
-               const NotificationSource& source,
-               const NotificationDetails& details);
+  virtual void Observe(NotificationType type,
+                       const NotificationSource& source,
+                       const NotificationDetails& details);
  private:
   // "Synthetic" event. Called from TabInsertedAt if new tab is detected.
   void TabCreatedAt(TabContents* contents, int index, bool foreground);
 
   // Internal processing of tab updated events. Is called by both TabChangedAt
   // and Observe/NAV_ENTRY_COMMITTED.
   void TabUpdated(TabContents* contents, bool did_navigate);
 
   // Packages |changed_properties| as a tab updated event for the tab |contents|
   // and dispatches the event to the extension.
@@ skipping 75 matching lines @@
   int focused_window_id_;
 
   // The main profile (non-OTR) profile which will be used to send events not
   // associated with any browser.
   Profile* profile_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionBrowserEventRouter);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_BROWSER_EVENT_ROUTER_H_