Native themes: Add menu separator part

ui/views/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 import("//ui/base/ui_features.gni")
 import("//ui/ozone/ozone.gni")
 
@@ skipping 160 matching lines @@
     "controls/menu/menu_runner_handler.h",
     "controls/menu/menu_runner_impl.cc",
     "controls/menu/menu_runner_impl.h",
     "controls/menu/menu_runner_impl_adapter.cc",
     "controls/menu/menu_runner_impl_adapter.h",
     "controls/menu/menu_runner_impl_cocoa.h",
     "controls/menu/menu_runner_impl_cocoa.mm",
     "controls/menu/menu_runner_impl_interface.h",
     "controls/menu/menu_scroll_view_container.cc",
     "controls/menu/menu_scroll_view_container.h",
+    "controls/menu/menu_separator.cc",
     "controls/menu/menu_separator.h",
-    "controls/menu/menu_separator_views.cc",
-    "controls/menu/menu_separator_win.cc",
     "controls/menu/menu_types.h",
     "controls/menu/native_menu_win.cc",
     "controls/menu/native_menu_win.h",
     "controls/menu/submenu_view.cc",
     "controls/menu/submenu_view.h",
     "controls/message_box_view.cc",
     "controls/message_box_view.h",
     "controls/native/native_view_host.cc",
     "controls/native/native_view_host.h",
     "controls/native/native_view_host_mac.h",
@@ skipping 829 matching lines @@
       "//ui/base:test_support",
       "//ui/compositor",
       "//ui/events:test_support",
       "//ui/gl:test_support",
       "//ui/resources",
       "//ui/resources:ui_test_pak",
       "//ui/strings",
     ]
   }
 }