Added Ash.SystemMenu.DefaultView.VisibleItems histogram.

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.cc',
@@ skipping 255 matching lines @@
       'common/system/tray/tray_background_view.cc',
       'common/system/tray/tray_background_view.h',
       'common/system/tray/tray_bar_button_with_title.cc',
       'common/system/tray/tray_bar_button_with_title.h',
       'common/system/tray/tray_bubble_wrapper.cc',
       'common/system/tray/tray_bubble_wrapper.h',
       'common/system/tray/tray_constants.cc',
       'common/system/tray/tray_constants.h',
       'common/system/tray/tray_details_view.cc',
       'common/system/tray/tray_details_view.h',
-      'common/system/tray/tray_empty.cc',
-      'common/system/tray/tray_empty.h',
       'common/system/tray/tray_event_filter.cc',
       'common/system/tray/tray_event_filter.h',
       'common/system/tray/tray_image_item.cc',
       'common/system/tray/tray_image_item.h',
       'common/system/tray/tray_item_more.cc',
       'common/system/tray/tray_item_more.h',
       'common/system/tray/tray_item_view.cc',
       'common/system/tray/tray_item_view.h',
       'common/system/tray/tray_notification_view.cc',
       'common/system/tray/tray_notification_view.h',
@@ skipping 1168 matching lines @@
                   '../tools/xdisplaycheck/xdisplaycheck.gyp:xdisplaycheck',
                 ],
               }
             ],
           ],
         },
       ],
     }],
   ],
 }