Add extensions code to use common updater in components/update_client/

chrome/chrome_browser_extensions.gypi

 # Copyright (c) 2013 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': {
     'chrome_browser_extensions_chromeos_sources': [
       'browser/extensions/api/cast_devices_private/cast_devices_private_api.cc',
       'browser/extensions/api/cast_devices_private/cast_devices_private_api.h',
       'browser/extensions/api/certificate_provider/certificate_provider_api.cc',
@@ skipping 833 matching lines @@
       'browser/extensions/theme_installed_infobar_delegate.cc',
       'browser/extensions/theme_installed_infobar_delegate.h',
       'browser/extensions/token_cache/token_cache_service.cc',
       'browser/extensions/token_cache/token_cache_service.h',
       'browser/extensions/token_cache/token_cache_service_factory.cc',
       'browser/extensions/token_cache/token_cache_service_factory.h',
       'browser/extensions/unpacked_installer.cc',
       'browser/extensions/unpacked_installer.h',
       'browser/extensions/updater/chrome_extension_downloader_factory.cc',
       'browser/extensions/updater/chrome_extension_downloader_factory.h',
+      'browser/extensions/updater/chrome_update_client_config.cc',
+      'browser/extensions/updater/chrome_update_client_config.h',
       'browser/extensions/updater/extension_updater.cc',
       'browser/extensions/updater/extension_updater.h',
       'browser/extensions/user_script_listener.cc',
       'browser/extensions/user_script_listener.h',
       'browser/extensions/warning_badge_service.cc',
       'browser/extensions/warning_badge_service.h',
       'browser/extensions/warning_badge_service_factory.cc',
       'browser/extensions/warning_badge_service_factory.h',
       'browser/extensions/webstore_data_fetcher.cc',
       'browser/extensions/webstore_data_fetcher.h',
@@ skipping 283 matching lines @@
           ],
         }, {  # use_brlapi==0
           'sources': [
             'browser/extensions/api/braille_display_private/braille_controller_stub.cc',
           ],
         }],
       ],
     },
   ],
 }