MenuButton: support Mac look & feel

ui/views/controls/button/menu_button.h

Index: ui/views/controls/button/menu_button.h
diff --git a/ui/views/controls/button/menu_button.h b/ui/views/controls/button/menu_button.h
index 696a94146f3f9868e01e2eca55a00dfab53f5e8e..f685ceb87c2463ab86fe49d5f407ae485851069c 100644
--- a/ui/views/controls/button/menu_button.h
+++ b/ui/views/controls/button/menu_button.h
@@ -53,12 +53,6 @@ class VIEWS_EXPORT MenuButton : public LabelButton {
              bool show_menu_marker);
   ~MenuButton() override;
 
-  bool show_menu_marker() const { return show_menu_marker_; }
-  void set_menu_marker(const gfx::ImageSkia* menu_marker) {
-    menu_marker_ = menu_marker;
-  }
-  const gfx::ImageSkia* menu_marker() const { return menu_marker_; }
-
   const gfx::Point& menu_offset() const { return menu_offset_; }
   void set_menu_offset(int x, int y) { menu_offset_.SetPoint(x, y); }
 
@@ -128,10 +122,7 @@ class VIEWS_EXPORT MenuButton : public LabelButton {
   MenuButtonListener* listener_;
 
   // Whether or not we're showing a drop marker.
-  bool show_menu_marker_;
-
-  // The down arrow used to differentiate the menu button from normal buttons.
-  const gfx::ImageSkia* menu_marker_;
+  const bool show_menu_marker_;
 
   // If non-null the destructor sets this to true. This is set while the menu is
   // showing and used to detect if the menu was deleted while running.