Start building message_center on Mac.

ui/message_center/message_center.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': [
     {
       'target_name': 'message_center',
       'type': '<(component)',
       'dependencies': [
         '../../base/base.gyp:base',
         '../../base/base.gyp:base_i18n',
         '../../base/third_party/dynamic_annotations/dynamic_annotations.gyp:dynamic_annotations',
         '../../build/temp_gyp/googleurl.gyp:googleurl',
         '../../skia/skia.gyp:skia',
         '../base/strings/ui_strings.gyp:ui_strings',
         '../compositor/compositor.gyp:compositor',
         '../ui.gyp:ui',
         '../ui.gyp:ui_resources',
-        '../views/views.gyp:views',
       ],
       'defines': [
         'MESSAGE_CENTER_IMPLEMENTATION',
       ],
       'sources': [
         'message_center.cc',
         'message_center.h',
         'message_center_constants.cc',
         'message_center_constants.h',
         'message_center_export.h',
@@ skipping 25 matching lines @@
         'views/message_simple_view.h',
         'views/message_view.cc',
         'views/message_view.h',
         'views/notifier_settings_view.cc',
         'views/notifier_settings_view.h',
         'views/notification_view.cc',
         'views/notification_view.h',
       ],
       # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
       'msvs_disabled_warnings': [ 4267, ],
+      'conditions': [
+        ['toolkit_views==1', {
+          'dependencies': [
+            '../views/views.gyp:views',
+          ],
+        }, {
+          'sources/': [
+            ['exclude', 'views/'],
+          ],
+        }],
+      ],
     },
     {
       'target_name': 'message_center_unittests',
       'type': 'executable',
       'dependencies': [
         '../../base/base.gyp:base',
         '../../base/base.gyp:run_all_unittests',
         '../../base/base.gyp:test_support_base',
         '../../skia/skia.gyp:skia',
         '../../testing/gtest.gyp:gtest',
         '../ui.gyp:ui',
         'message_center',
       ],
       'sources': [
         'message_center_tray_unittest.cc',
         'notification_list_unittest.cc',
       ],
     },
   ],
 }