Add the button style for combobox

ui/views/views.gyp

 # Copyright (c) 2012 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.
 {
   'variables': {
     'chromium_code': 1,
   },
   'target_defaults': {
     'conditions': [
       ['use_aura==1', {
@@ skipping 118 matching lines @@
         'controls/menu/menu_host_root_view.h',
         'controls/menu/menu_insertion_delegate_win.h',
         'controls/menu/menu_item_view.cc',
         'controls/menu/menu_item_view.h',
         'controls/menu/menu_listener.cc',
         'controls/menu/menu_listener.h',
         'controls/menu/menu_model_adapter.cc',
         'controls/menu/menu_model_adapter.h',
         'controls/menu/menu_runner.cc',
         'controls/menu/menu_runner.h',
+        'controls/menu/menu_runner_core.h',
         'controls/menu/menu_scroll_view_container.cc',
         'controls/menu/menu_scroll_view_container.h',
         'controls/menu/menu_separator.h',
         'controls/menu/menu_separator_views.cc',
         'controls/menu/menu_separator_win.cc',
         'controls/menu/menu_win.cc',
         'controls/menu/menu_win.h',
         'controls/menu/menu_wrapper.h',
         'controls/menu/native_menu_win.cc',
         'controls/menu/native_menu_win.h',
@@ skipping 950 matching lines @@
           'sources/': [
             # This is needed because the aura rule strips it from the default
             # sources list.
             ['include', '^../../content/app/startup_helper_win.cc'],
           ],
         }],
       ],
     },  # target_name: views_examples_with_content_exe
   ],
 }