Standardize usage of virtual/override/final specifiers.

ash/keyboard_uma_event_filter.h

Index: ash/keyboard_uma_event_filter.h
diff --git a/ash/keyboard_uma_event_filter.h b/ash/keyboard_uma_event_filter.h
index 0928e7fb3d374fb20e2f1164ad0efcfd6dda3495..494ff6664fcfa3a93aa33c90a7279cabc7ae7e60 100644
--- a/ash/keyboard_uma_event_filter.h
+++ b/ash/keyboard_uma_event_filter.h
@@ -17,10 +17,10 @@ namespace ash {
 class KeyboardUMAEventFilter : public ui::EventHandler {
  public:
   KeyboardUMAEventFilter();
-  virtual ~KeyboardUMAEventFilter();
+  ~KeyboardUMAEventFilter() override;
 
   // ui::EventHandler overrides:
-  virtual void OnKeyEvent(ui::KeyEvent* event) override;
+  void OnKeyEvent(ui::KeyEvent* event) override;
 
  private:
   // The timestamp of the last character keystroke.