Write a NativeThemeGtk2 class for linux_aura.

chrome/browser/ui/libgtk2ui/libgtk2ui.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,
   },
   'targets': [
     {
@@ skipping 22 matching lines @@
       # the normal, global gtk exclusion rules, as we are otherwise using gtk
       # in a non-gtk build.
       'sources': [
         'chrome_gtk_frame.cc',
         'chrome_gtk_frame.h',
         'gtk2_ui.cc',
         'gtk2_ui.h',
         'gtk2_util.cc',
         'gtk2_util.h',
         'libgtk2ui_export.h',
+        'native_theme_gtk2.cc',
+        'native_theme_gtk2.h',
         'owned_widget_gtk2.cc',
         'owned_widget_gtk2.h',
         'select_file_dialog_impl.cc',
         'select_file_dialog_impl.h',
         'select_file_dialog_impl_gtk2.cc',
         'select_file_dialog_impl_kde.cc',
         'skia_utils_gtk2.cc',
         'skia_utils_gtk2.h',
       ],
     },
   ],
 }