Part 1 of work to do user sign in based on OAuth2:

chrome/chrome_common.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.
 
 {
   'targets': [
     {
       'target_name': 'common',
       'type': 'static_library',
       'variables': {
@@ skipping 360 matching lines @@
         'common/net/gaia/gaia_authenticator.cc',
         'common/net/gaia/gaia_authenticator.h',
         'common/net/gaia/gaia_oauth_client.cc',
         'common/net/gaia/gaia_oauth_client.h',
         'common/net/gaia/gaia_urls.cc',
         'common/net/gaia/gaia_urls.h',
         'common/net/gaia/google_service_auth_error.cc',
         'common/net/gaia/google_service_auth_error.h',
         'common/net/gaia/oauth_request_signer.cc',
         'common/net/gaia/oauth_request_signer.h',
+        'common/net/gaia/oauth2_access_token_consumer.h',
+        'common/net/gaia/oauth2_access_token_fetcher.cc',
+        'common/net/gaia/oauth2_access_token_fetcher.h',
         'common/net/x509_certificate_model.cc',
         'common/net/x509_certificate_model_nss.cc',
         'common/net/x509_certificate_model_openssl.cc',
         'common/net/x509_certificate_model.h',
       ],
       'dependencies': [
         'chrome_resources.gyp:chrome_resources',
         'chrome_resources.gyp:chrome_strings',
         '../base/base.gyp:base',
         '../crypto/crypto.gyp:crypto',
@@ skipping 40 matching lines @@
         'common/safe_browsing/csd.proto'
       ],
       'variables': {
         'proto_in_dir': 'common/safe_browsing',
         'proto_out_dir': 'chrome/common/safe_browsing',
       },
       'includes': [ '../build/protoc.gypi' ],
     },
   ],
 }