[Chrome OS MD] Draw a 1px separator between 2 tray items

ash/ash.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,
     # These files lists are shared with the GN build.
     'ash_sources': [
       'accelerators/accelerator_commands_aura.cc',
@@ skipping 242 matching lines @@
       'common/system/networking_config_delegate.cc',
       'common/system/networking_config_delegate.h',
       'common/system/overview/overview_button_tray.cc',
       'common/system/overview/overview_button_tray.h',
       'common/system/status_area_widget.cc',
       'common/system/status_area_widget.h',
       'common/system/status_area_widget_delegate.cc',
       'common/system/status_area_widget_delegate.h',
       'common/system/system_notifier.cc',
       'common/system/system_notifier.h',
+      'common/system/view_observer.h',
       'common/system/toast/toast_data.cc',
       'common/system/toast/toast_data.h',
       'common/system/toast/toast_manager.cc',
       'common/system/toast/toast_manager.h',
       'common/system/toast/toast_overlay.cc',
       'common/system/toast/toast_overlay.h',
       'common/system/tray/actionable_view.cc',
       'common/system/tray/actionable_view.h',
       'common/system/tray/default_system_tray_delegate.cc',
       'common/system/tray/default_system_tray_delegate.h',
@@ skipping 1200 matching lines @@
                   '../tools/xdisplaycheck/xdisplaycheck.gyp:xdisplaycheck',
                 ],
               }
             ],
           ],
         },
       ],
     }],
   ],
 }