Created initial multi-item notification view

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 23 matching lines @@
         'message_center_bubble.h',
         'message_center_export.h',
         'message_popup_bubble.cc',
         'message_popup_bubble.h',
         'message_simple_view.cc',
         'message_simple_view.h',
         'message_view.cc',
         'message_view.h',
         'message_view_factory.cc',
         'message_view_factory.h',
+        'message_view_multiple.cc',
+        'message_view_multiple.h',
         'notification_list.cc',
         'notification_list.h',
       ],
     },
   ],
 }