Add chrome/browser/ui to the GN build.

ash/ash_strings.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.
 
 {
   'targets': [
     {
+      # GN version: //ash/strings
       'target_name': 'ash_strings',
       'type': 'none',
       'variables': {
         'grit_out_dir': '<(SHARED_INTERMEDIATE_DIR)/ash/strings',
       },
       'actions': [
         {
           'action_name': 'generate_ash_strings',
           'variables': {
             'grit_grd_file': 'ash_strings.grd',
           },
           'includes': [ '../build/grit_action.gypi' ],
         },
       ],
       'includes': [ '../build/grit_target.gypi' ],
     },
   ],
 }