Standardize usage of virtual/override/final specifiers.

ash/wm/gestures/tray_gesture_handler.h

Index: ash/wm/gestures/tray_gesture_handler.h
diff --git a/ash/wm/gestures/tray_gesture_handler.h b/ash/wm/gestures/tray_gesture_handler.h
index 68ecf959a87e0ef8fc3d3b9a3aacdcb15006410c..529349868c81c453cb754b37731bd2071794ef83 100644
--- a/ash/wm/gestures/tray_gesture_handler.h
+++ b/ash/wm/gestures/tray_gesture_handler.h
@@ -19,7 +19,7 @@ namespace ash {
 class TrayGestureHandler : public views::WidgetObserver {
  public:
   TrayGestureHandler();
-  virtual ~TrayGestureHandler();
+  ~TrayGestureHandler() override;
 
   // Handles a gesture-update event and updates the dragging state of the tray
   // bubble. Returns true if the handler can continue to process gesture events
@@ -30,7 +30,7 @@ class TrayGestureHandler : public views::WidgetObserver {
   void CompleteGestureDrag(const ui::GestureEvent& event);
 
  private:
-  virtual void OnWidgetDestroying(views::Widget* widget) override;
+  void OnWidgetDestroying(views::Widget* widget) override;
 
   // The widget for the tray-bubble.
   views::Widget* widget_;