Implement oauth token external handler checking.

chrome/chrome_browser_chromeos.gypi

 # 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.
 
 {
   'variables': {
     # These files lists are shared with the GN build.
     'browser_chromeos_sources': [
         # All .cc, .h, .m, and .mm files under browser/chromeos, except for tests
@@ skipping 581 matching lines @@
         'browser/chromeos/login/signin/merge_session_xhr_request_waiter.cc',
         'browser/chromeos/login/signin/merge_session_xhr_request_waiter.h',
         'browser/chromeos/login/signin/oauth2_login_manager.cc',
         'browser/chromeos/login/signin/oauth2_login_manager.h',
         'browser/chromeos/login/signin/oauth2_login_manager_factory.cc',
         'browser/chromeos/login/signin/oauth2_login_manager_factory.h',
         'browser/chromeos/login/signin/oauth2_login_verifier.cc',
         'browser/chromeos/login/signin/oauth2_login_verifier.h',
         'browser/chromeos/login/signin/oauth2_token_fetcher.cc',
         'browser/chromeos/login/signin/oauth2_token_fetcher.h',
+        'browser/chromeos/login/signin/token_handler_util.cc',
+        'browser/chromeos/login/signin/token_handler_util.h',
         'browser/chromeos/login/signin_screen_controller.cc',
         'browser/chromeos/login/signin_screen_controller.h',
         'browser/chromeos/login/signin_specifics.cc',
         'browser/chromeos/login/signin_specifics.h',
         'browser/chromeos/login/startup_utils.cc',
         'browser/chromeos/login/startup_utils.h',
         'browser/chromeos/login/supervised/supervised_user_authentication.cc',
         'browser/chromeos/login/supervised/supervised_user_authentication.h',
         'browser/chromeos/login/supervised/supervised_user_authenticator.cc',
         'browser/chromeos/login/supervised/supervised_user_authenticator.h',
@@ skipping 697 matching lines @@
         'browser/chromeos/attestation/attestation_signed_data.proto',
       ],
       'variables': {
         'proto_in_dir': 'browser/chromeos/attestation',
         'proto_out_dir': 'chrome/browser/chromeos/attestation',
       },
       'includes': [ '../build/protoc.gypi' ]
     },
   ],
 }