Standardize usage of virtual/override/final specifiers.

ui/aura/window_tracker.h

 // Copyright (c) 2012 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 UI_AURA_WINDOW_TRACKER_H_
 #define UI_AURA_WINDOW_TRACKER_H_
 
 #include <set>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "ui/aura/aura_export.h"
 #include "ui/aura/window_observer.h"
 
 namespace aura {
 
 // This class keeps track of a set of windows. A Window is removed either
 // explicitly by Remove(), or implicitly when the window is destroyed.
 class AURA_EXPORT WindowTracker : public WindowObserver {
  public:
   typedef std::set<Window*> Windows;
 
   WindowTracker();
-  virtual ~WindowTracker();
+  ~WindowTracker() override;
 
   // Returns the set of windows being observed.
   const std::set<Window*>& windows() const { return windows_; }
 
   // Adds |window| to the set of Windows being tracked.
   void Add(Window* window);
 
   // Removes |window| from the set of windows being tracked.
   void Remove(Window* window);
 
   // Returns true if |window| was previously added and has not been removed or
   // deleted.
   bool Contains(Window* window);
 
   // WindowObserver overrides:
-  virtual void OnWindowDestroying(Window* window) override;
+  void OnWindowDestroying(Window* window) override;
 
  private:
   Windows windows_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowTracker);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_WINDOW_TRACKER_H_