Implement message center on Windows

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': [
     {
@@ skipping 16 matching lines @@
       'sources': [
         'message_bubble_base.cc',
         'message_bubble_base.h',
         'message_center.cc',
         'message_center.h',
         'message_center_bubble.cc',
         'message_center_bubble.h',
         'message_center_constants.cc',
         'message_center_constants.h',
         'message_center_export.h',
+        'message_center_tray.cc',
+        'message_center_tray.h',
+        'message_center_tray_delegate.h',
         'message_center_switches.cc',
         'message_center_switches.h',
         'message_popup_bubble.cc',
         'message_popup_bubble.h',
         'message_view.cc',
         'message_view.h',
         'notification_list.cc',
         'notification_list.h',
         'notification_view.cc',
         'notification_view.h',
         'notifier_settings.cc',
         'notifier_settings.h',
         'quiet_mode_bubble.cc',
         'quiet_mode_bubble.h',
       ],
     },
     {
       'target_name': 'message_center_unittests',
       'type': 'executable',
       'dependencies': [
         '../../base/base.gyp:base',
         '../../base/base.gyp:test_support_base',
         '../../skia/skia.gyp:skia',
         '../../testing/gtest.gyp:gtest',
         '../../testing/gtest.gyp:gtest_main',
         '../ui.gyp:ui',
         'message_center',
       ],
       'sources': [
+        'message_center_tray_unittest.cc',
         'notification_list_unittest.cc',
       ],
     },
   ],
 }