Standardize usage of virtual/override/final specifiers.

ash/shell/context_menu.h

Index: ash/shell/context_menu.h
diff --git a/ash/shell/context_menu.h b/ash/shell/context_menu.h
index 53dc75d9d308888debbbce8d4ac3794a77535671..7126298789d58211542e1eb6db32dc4d7900fa8c 100644
--- a/ash/shell/context_menu.h
+++ b/ash/shell/context_menu.h
@@ -22,15 +22,14 @@ class ContextMenu : public ui::SimpleMenuModel,
                     public ui::SimpleMenuModel::Delegate {
  public:
   explicit ContextMenu(aura::Window* root);
-  virtual ~ContextMenu();
+  ~ContextMenu() override;
 
   // ui::SimpleMenuModel::Delegate overrides:
-  virtual bool IsCommandIdChecked(int command_id) const override;
-  virtual bool IsCommandIdEnabled(int command_id) const override;
-  virtual bool GetAcceleratorForCommandId(
-      int command_id,
-      ui::Accelerator* accelerator) override;
-  virtual void ExecuteCommand(int command_id, int event_flags) override;
+  bool IsCommandIdChecked(int command_id) const override;
+  bool IsCommandIdEnabled(int command_id) const override;
+  bool GetAcceleratorForCommandId(int command_id,
+                                  ui::Accelerator* accelerator) override;
+  void ExecuteCommand(int command_id, int event_flags) override;
 
  private:
   enum MenuItem {