Enables hot-tracking for overflow extension buttons in the app menu

ui/views/controls/menu/menu_controller.h

Index: ui/views/controls/menu/menu_controller.h
diff --git a/ui/views/controls/menu/menu_controller.h b/ui/views/controls/menu/menu_controller.h
index 43c3c0ee55ee8af7300c9dab2c7bf62b9f3ac7b6..58325fe52cda550397887b8de5993a399df61cca 100644
--- a/ui/views/controls/menu/menu_controller.h
+++ b/ui/views/controls/menu/menu_controller.h
@@ -565,6 +565,13 @@ class VIEWS_EXPORT MenuController : public WidgetObserver {
   void HandleMouseLocation(SubmenuView* source,
                            const gfx::Point& mouse_location);
 
+  // Updates the current |hot_button_| and its hot tracked state.
+  void SetHotTrackedButton(CustomButton* hot_button, bool is_hot_tracked);
+
+  // Sets hot-tracked state to the first focusable descendant view of |item|.
+  void SetInitialHotTrackedView(MenuItemView* item,
+                                SelectionIncrementDirectionType direction);
+
   // The active instance.
   static MenuController* active_instance_;
 
@@ -663,6 +670,9 @@ class VIEWS_EXPORT MenuController : public WidgetObserver {
   // See UpdateActiveMouseView() for details.
   const int active_mouse_view_id_;
 
+  // Current hot tracked view if any.
+  CustomButton* hot_button_;
+
   internal::MenuControllerDelegate* delegate_;
 
   // How deep we are in nested message loops. This should be at most 2 (when