Re-enable about:flags on Android

chrome/chrome_browser_ui.gypi

 # Copyright 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': [
     {
       'target_name': 'browser_ui',
       'type': 'static_library',
       'variables': { 'enable_wexit_time_destructors': 1, },
@@ skipping 2576 matching lines @@
           ],
           'sources/': [
             ['exclude', '^browser/ui/omnibox/'],
             ['exclude', '^browser/ui/panels/'],
             ['exclude', '^browser/ui/pdf/'],
             ['exclude', '^browser/ui/startup/'],
             ['exclude', '^browser/ui/tabs/'],
             ['exclude', '^browser/ui/toolbar/'],
             ['exclude', '^browser/ui/webui/downloads_'],
             ['exclude', '^browser/ui/webui/feedback_'],
-            ['exclude', '^browser/ui/webui/flags_'],
             ['exclude', '^browser/ui/webui/help/'],
             ['exclude', '^browser/ui/webui/inspect_'],
             ['exclude', '^browser/ui/webui/options'],
             ['exclude', '^browser/ui/webui/options'],
             ['exclude', '^browser/ui/webui/signin/'],
             ['exclude', '^browser/ui/webui/suggestions_internals'],
             ['exclude', '^browser/ui/webui/sync_promo'],
             ['exclude', '^browser/ui/webui/uber'],
           ],
         }],
@@ skipping 207 matching lines @@
         }],
         ['enable_message_center==1', {
           'dependencies': [
             '../ui/message_center/message_center.gyp:message_center',
           ],
         }],
       ],
     },
   ],
 }