[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 26 matching lines @@
         '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',
         'native_theme_win.cc',
         'native_theme_win.h',
       ],
+      'conditions': [
+        ['OS=="win"', {
+          'sources': [
+            'native_theme_win_dark.cc',
+            'native_theme_win_dark.h',
+          ],
+        }],
+        ['use_aura==1', {
+          'sources': [
+            'native_theme_aura_dark.cc',
+            'native_theme_aura_dark.h',
+          ],
+        }],
+      ],
     },
     {
       'target_name': 'native_theme_unittests',
       'type': '<(gtest_target_type)',
       'dependencies': [
         '../../base/base.gyp:base',
         '../../base/base.gyp:test_support_base',
         '../../skia/skia.gyp:skia',
         '../../testing/gtest.gyp:gtest',
         'native_theme',
       ],
       'sources': [
         '../../base/test/run_all_unittests.cc',
         'native_theme_mac_unittest.cc',
       ],
     },
   ],
 }