[MD] Implement incognito colors as a NativeTheme (for Aura).

ui/native_theme/native_theme.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 13 matching lines @@
       ],
       'sources': [
         'common_theme.cc',
         'common_theme.h',
         'native_theme.cc',
         'native_theme.h',
         'native_theme_android.cc',
         'native_theme_android.h',
         'native_theme_aura.cc',
         'native_theme_aura.h',
+        'native_theme_aura_dark.cc',
+        'native_theme_aura_dark.h',
         'native_theme_aurawin.cc',
         'native_theme_aurawin.h',
         'native_theme_base.cc',
         'native_theme_base.h',
         'native_theme_mac.h',
         'native_theme_mac.mm',
         'native_theme_observer.cc',
         'native_theme_observer.h',
         'native_theme_switches.cc',
         'native_theme_switches.h',
@@ skipping 11 matching lines @@
         '../../testing/gtest.gyp:gtest',
         'native_theme',
       ],
       'sources': [
         '../../base/test/run_all_unittests.cc',
         'native_theme_mac_unittest.cc',
       ],
     },
   ],
 }