Add the layout test case of ash/popup_message.

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 769 matching lines @@
       'extended_desktop_unittest.cc',
       'focus_cycler_unittest.cc',
       'frame/caption_buttons/frame_caption_button_container_view_unittest.cc',
       'frame/caption_buttons/frame_size_button_unittest.cc',
       'frame/custom_frame_view_ash_unittest.cc',
       'frame/default_header_painter_unittest.cc',
       'host/ash_window_tree_host_x11_unittest.cc',
       'keyboard_overlay/keyboard_overlay_delegate_unittest.cc',
       'keyboard_overlay/keyboard_overlay_view_unittest.cc',
       'magnifier/magnification_controller_unittest.cc',
+      'popup_message_unittest.cc',
       'root_window_controller_unittest.cc',
       'screen_util_unittest.cc',
       'shelf/scoped_observer_with_duplicated_sources_unittest.cc',
       'shelf/shelf_layout_manager_unittest.cc',
       'shelf/shelf_model_unittest.cc',
       'shelf/shelf_navigator_unittest.cc',
       'shelf/shelf_tooltip_manager_unittest.cc',
       'shelf/shelf_unittest.cc',
       'shelf/shelf_view_unittest.cc',
       'shelf/shelf_widget_unittest.cc',
@@ skipping 509 matching lines @@
                   '../tools/xdisplaycheck/xdisplaycheck.gyp:xdisplaycheck',
                 ],
               }
             ],
           ],
         },
       ],
     }],
   ],
 }