Standardize usage of virtual/override/final specifiers.

ui/views/examples/button_example.h

Index: ui/views/examples/button_example.h
diff --git a/ui/views/examples/button_example.h b/ui/views/examples/button_example.h
index 8fc2c60d524653ab7cdf71c91a19b0d373df797a..566d3f09bf2e085c68902fa462a67ac037688e81 100644
--- a/ui/views/examples/button_example.h
+++ b/ui/views/examples/button_example.h
@@ -21,16 +21,16 @@ class VIEWS_EXAMPLES_EXPORT ButtonExample : public ExampleBase,
                                             public ButtonListener {
  public:
   ButtonExample();
-  virtual ~ButtonExample();
+  ~ButtonExample() override;
 
   // ExampleBase:
-  virtual void CreateExampleView(View* container) override;
+  void CreateExampleView(View* container) override;
 
  private:
   void LabelButtonPressed(const ui::Event& event);
 
   // ButtonListener:
-  virtual void ButtonPressed(Button* sender, const ui::Event& event) override;
+  void ButtonPressed(Button* sender, const ui::Event& event) override;
 
   // Example buttons.
   LabelButton* label_button_;