Exclude extension settings strings for platforms that don't have extensions.

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 3058 matching lines @@
             'browser/ui/sync/browser_synced_window_delegate.cc',
             'browser/ui/tab_contents/tab_contents_iterator.cc',
             'browser/ui/uma_browsing_activity_observer.cc',
             'browser/ui/uma_browsing_activity_observer.h',
             'browser/ui/webui/bookmarks_ui.cc',
             'browser/ui/webui/bookmarks_ui.h',
             'browser/ui/webui/certificate_viewer_webui.cc',
             'browser/ui/webui/extensions/command_handler.cc',
             'browser/ui/webui/extensions/extension_settings_handler.cc',
             'browser/ui/webui/extensions/extension_settings_handler.h',
+            'browser/ui/webui/extensions/extension_error_handler.cc',
+            'browser/ui/webui/extensions/extension_error_handler.h',
             'browser/ui/webui/extensions/extensions_ui.cc',
             'browser/ui/webui/extensions/install_extension_handler.cc',
             'browser/ui/webui/identity_internals_ui.cc',
             'browser/ui/webui/identity_internals_ui.h',
             'browser/ui/webui/inspect_ui.cc',
             'browser/ui/webui/inspect_ui.h',
             'browser/ui/webui/ntp/app_launcher_handler.cc',
             'browser/ui/webui/ntp/app_launcher_handler.h',
             'browser/ui/webui/ntp/new_tab_page_handler.cc',
             'browser/ui/webui/ntp/new_tab_page_handler.h',
@@ skipping 311 matching lines @@
             'browser/ui/webui/local_discovery/local_discovery_ui.cc',
             'browser/ui/webui/local_discovery/local_discovery_ui.h',
             'browser/ui/webui/local_discovery/local_discovery_ui_handler.cc',
             'browser/ui/webui/local_discovery/local_discovery_ui_handler.h',
           ],
         }],
       ],
     },
   ],
 }