Add ArcNotificationManager for new ARC 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': [
+    {
+      'target_name': 'arc',
+      'type': 'static_library',
+      'include_dirs': [
+        '..',
+      ],
+      'dependencies': [
+        '../../skia/skia.gyp:skia',
+        '../../components/components.gyp:arc_mojo_bindings',
+      ],
+      'sources': [
+        'notification/arc_notification_manager.cc',
+        'notification/arc_notification_manager.h',
+        'notification/arc_notification_item.cc',
+        'notification/arc_notification_item.h',
+      ],
+    },
+  ],
+}