Use a single views::MenuConfig instance for each platform

ui/views/controls/menu/menu_config_mac.mm

Index: ui/views/controls/menu/menu_config_mac.mm
diff --git a/ui/views/controls/menu/menu_config_mac.mm b/ui/views/controls/menu/menu_config_mac.mm
index 78d6a2cc7f5fc7bdfd9e0351403c68026a5f1c7f..9c73a1f23891603a7433d1b8042024d41e3bebce 100644
--- a/ui/views/controls/menu/menu_config_mac.mm
+++ b/ui/views/controls/menu/menu_config_mac.mm
@@ -6,14 +6,9 @@
 
 #import <AppKit/AppKit.h>
 
-#include "ui/gfx/image/image_skia.h"
-#include "ui/native_theme/native_theme_mac.h"
-#include "ui/views/controls/menu/menu_image_util.h"
-
 namespace views {
 
-void MenuConfig::Init(const ui::NativeTheme* theme) {
-  DCHECK_EQ(theme, ui::NativeThemeMac::instance());
+void MenuConfig::Init() {
   font_list = gfx::FontList(gfx::Font([NSFont menuFontOfSize:0.0]));
   menu_vertical_border_size = 4;
   item_top_margin = item_no_icon_top_margin = 1;
@@ -33,10 +28,4 @@ void MenuConfig::Init(const ui::NativeTheme* theme) {
   use_outer_border = false;
 }
 
-// static
-const MenuConfig& MenuConfig::instance(const ui::NativeTheme* theme) {
-  CR_DEFINE_STATIC_LOCAL(MenuConfig, mac_instance, (theme));
-  return mac_instance;
-}
-
 }  // namespace views