Standardize usage of virtual/override/final specifiers.

ash/keyboard_overlay/keyboard_overlay_delegate.cc

Index: ash/keyboard_overlay/keyboard_overlay_delegate.cc
diff --git a/ash/keyboard_overlay/keyboard_overlay_delegate.cc b/ash/keyboard_overlay/keyboard_overlay_delegate.cc
index 84daf8da9ba693e33632b0fd8b5336a04f0a5a72..76563f5b80efc90fde9224d13c2123cf36f9241f 100644
--- a/ash/keyboard_overlay/keyboard_overlay_delegate.cc
+++ b/ash/keyboard_overlay/keyboard_overlay_delegate.cc
@@ -33,10 +33,10 @@ class PaintMessageHandler
       public base::SupportsWeakPtr<PaintMessageHandler> {
  public:
   explicit PaintMessageHandler(views::Widget* widget) : widget_(widget) {}
-  virtual ~PaintMessageHandler() {}
+  ~PaintMessageHandler() override {}
 
   // WebUIMessageHandler implementation.
-  virtual void RegisterMessages() override;
+  void RegisterMessages() override;
 
  private:
   void DidPaint(const base::ListValue* args);