MacViews: draw combobox arrow backgrounds

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,
     # Sources lists shared with GN build.
     'views_sources': [
       'accessibility/native_view_accessibility.cc',
       'accessibility/native_view_accessibility.h',
@@ skipping 272 matching lines @@
       'painter.cc',
       'painter.h',
       'rect_based_targeting_utils.cc',
       'rect_based_targeting_utils.h',
       'repeat_controller.cc',
       'repeat_controller.h',
       'round_rect_painter.cc',
       'round_rect_painter.h',
       'shadow_border.cc',
       'shadow_border.h',
+      'style/mac/combobox_background_mac.cc',
+      'style/mac/combobox_background_mac.h',
       'style/mac/dialog_button_border_mac.cc',
       'style/mac/dialog_button_border_mac.h',
       'style/platform_style.cc',
       'style/platform_style.h',
       'style/platform_style_mac.mm',
       'view.cc',
       'view.h',
       'view_constants.cc',
       'view_constants.h',
       'view_model.cc',
@@ skipping 713 matching lines @@
                 '../aura/aura.gyp:aura',
                 '../wm/wm.gyp:wm',
               ],
             }],
           ],
         },  # target_name: macviews_interactive_ui_tests
       ],  # targets
     }],
   ],  # conditions
 }