Add a floating close button for arc custom notification

ui/arc/arc.gyp

 # Copyright 2016 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': [
     {
       # GN: //ui/arc:arc
       'target_name': 'arc',
       'type': 'static_library',
       'include_dirs': [
         '../..',
       ],
       'dependencies': [
+        '../base/ui_base.gyp:ui_base',
         '../gfx/gfx.gyp:gfx_geometry',
         '../message_center/message_center.gyp:message_center',
+        '../resources/ui_resources.gyp:ui_resources',
+        '../strings/ui_strings.gyp:ui_strings',
+        '../views/views.gyp:views',
+        '../../ash/ash.gyp:ash',
         '../../base/base.gyp:base',
         '../../url/url.gyp:url_lib',
         '../../skia/skia.gyp:skia',
+        '../../components/components.gyp:arc_base',
         '../../components/components.gyp:arc_mojo_bindings',
+        '../../components/components.gyp:exo',
         '../../components/components.gyp:signin_core_account_id',
       ],
       'sources': [
         'notification/arc_custom_notification_view.cc',
         'notification/arc_custom_notification_view.h',
         'notification/arc_custom_notification_item.cc',
         'notification/arc_custom_notification_item.h',
         'notification/arc_notification_item.cc',
         'notification/arc_notification_item.h',
         'notification/arc_notification_manager.cc',
@@ skipping 19 matching lines @@
         '../message_center/message_center.gyp:message_center_test_support',
         'arc',
       ],
       'sources': [
         'notification/arc_notification_manager_unittest.cc',
         'test/run_all_unittests.cc',
       ],
     },
   ],
 }