Remove BrowserSignin, as it's not used anywhere.

chrome/chrome_tests.gypi

 # Copyright (c) 2011 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' : {
     'pyautolib_sources': [
       'app/chrome_command_ids.h',
       'app/chrome_dll_resource.h',
       'common/automation_constants.h',
@@ skipping 2498 matching lines @@
         'browser/extensions/extension_test_message_listener.h',
         'browser/extensions/extension_toolbar_model_browsertest.cc',
         'browser/extensions/extension_tts_apitest.cc',
         'browser/extensions/extension_url_rewrite_browsertest.cc',
         'browser/extensions/extension_web_socket_proxy_private_apitest.cc',
         'browser/extensions/extension_webglbackground_apitest.cc',
         'browser/extensions/extension_webnavigation_apitest.cc',
         'browser/extensions/extension_webrequest_apitest.cc',
         'browser/extensions/extension_websocket_apitest.cc',
         'browser/extensions/extension_webstore_private_apitest.cc',
-        'browser/extensions/extension_webstore_private_browsertest.cc',
         'browser/extensions/isolated_app_apitest.cc',
         'browser/extensions/notifications_apitest.cc',
         'browser/extensions/page_action_apitest.cc',
         'browser/extensions/permissions_apitest.cc',
         'browser/extensions/stubs_apitest.cc',
         'browser/extensions/webstore_inline_install_browsertest.cc',
         'browser/extensions/window_open_apitest.cc',
         'browser/first_run/first_run_browsertest.cc',
         'browser/geolocation/access_token_store_browsertest.cc',
         'browser/geolocation/geolocation_browsertest.cc',
@@ skipping 1586 matching lines @@
               # Use outputs of this action as inputs for the main target build.
               # Seems as a misnomer but makes this happy on Linux (scons).
               'process_outputs_as_sources': 1,
             },
           ],  # 'actions'
         },
       ]
     }],  # 'coverage!=0'
   ],  # 'conditions'
 }