Standardize usage of virtual/override/final specifiers.

ui/views/linux_ui/window_button_order_provider.cc

Index: ui/views/linux_ui/window_button_order_provider.cc
diff --git a/ui/views/linux_ui/window_button_order_provider.cc b/ui/views/linux_ui/window_button_order_provider.cc
index fa65cabe4ce83cbe5eccafb98e658dd0e694abe9..22b8ffd5f4fb0a16a0ecbe9ef55547bd74d240c2 100644
--- a/ui/views/linux_ui/window_button_order_provider.cc
+++ b/ui/views/linux_ui/window_button_order_provider.cc
@@ -15,12 +15,13 @@ class WindowButtonOrderObserverDelegate : public WindowButtonOrderProvider,
                                           public WindowButtonOrderObserver {
  public:
   WindowButtonOrderObserverDelegate();
-  virtual ~WindowButtonOrderObserverDelegate();
+  ~WindowButtonOrderObserverDelegate() override;
 
   // WindowButtonOrderObserver:
-  virtual void OnWindowButtonOrderingChange(
+  void OnWindowButtonOrderingChange(
       const std::vector<views::FrameButton>& leading_buttons,
       const std::vector<views::FrameButton>& trailing_buttons) override;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(WindowButtonOrderObserverDelegate);
 };