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

chrome/browser/ui/views/notifications/balloon_view.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.
 
 // Draws the view for the balloons.
 
 #ifndef CHROME_BROWSER_UI_VIEWS_NOTIFICATIONS_BALLOON_VIEW_H_
 #define CHROME_BROWSER_UI_VIEWS_NOTIFICATIONS_BALLOON_VIEW_H_
 #pragma once
 
@@ skipping 54 matching lines @@
  private:
   // views::View interface.
   virtual void Paint(gfx::Canvas* canvas);
   virtual void DidChangeBounds(const gfx::Rect& previous,
                                const gfx::Rect& current);
   virtual gfx::Size GetPreferredSize() {
     return gfx::Size(1000, 1000);
   }
 
   // views::ViewMenuDelegate interface.
-  void RunMenu(views::View* source, const gfx::Point& pt);
+  virtual void RunMenu(views::View* source, const gfx::Point& pt);
 
   // views::WidgetDelegate interface.
-  void DisplayChanged();
-  void WorkAreaChanged();
+  virtual void DisplayChanged();
+  virtual void WorkAreaChanged();
 
   // views::ButtonListener interface.
   virtual void ButtonPressed(views::Button* sender, const views::Event&);
 
   // NotificationObserver interface.
   virtual void Observe(NotificationType type,
                        const NotificationSource& source,
                        const NotificationDetails& details);
 
   // AnimationDelegate interface.
@@ skipping 73 matching lines @@
   scoped_ptr<NotificationOptionsMenuModel> options_menu_model_;
   scoped_ptr<views::Menu2> options_menu_menu_;
   views::MenuButton* options_menu_button_;
 
   NotificationRegistrar notification_registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(BalloonViewImpl);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_NOTIFICATIONS_BALLOON_VIEW_H_