Change Views menus to consistently use GetNativeTheme for theming.

ui/views/controls/menu/menu_config.cc

Index: ui/views/controls/menu/menu_config.cc
diff --git a/ui/views/controls/menu/menu_config.cc b/ui/views/controls/menu/menu_config.cc
index 4d1bb537a5317a9b3c0d27e4226b39d7a7bd6539..0d726c54002850a39de29abc159f74116f0b5bae 100644
--- a/ui/views/controls/menu/menu_config.cc
+++ b/ui/views/controls/menu/menu_config.cc
@@ -40,7 +40,6 @@ MenuConfig::MenuConfig(const ui::NativeTheme* theme)
       use_outer_border(true),
       icons_in_label(false),
       check_selected_combobox_item(false),
-      native_theme(theme),
       show_delay(400),
       corner_radius(0) {
   Init(theme);