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

chrome/common/net/gaia/gaia_constants.cc

 // 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.
 //
 // Constants definitions
 
 #include "chrome/common/net/gaia/gaia_constants.h"
 
 namespace GaiaConstants {
 
@@ skipping 26 matching lines @@
 const char kCWSService[] = "chromewebstore";
 const char kCWSNotificationScope[] =
     "https://www.googleapis.com/auth/chromewebstore.notification";
 
 // Service for LSO endpoint of Google that exposes OAuth APIs.
 const char kLSOService[] = "lso";
 
 // Used to mint uber auth tokens when needed.
 const char kGaiaSid[] = "sid";
 const char kGaiaLsid[] = "lsid";
-extern const char kGaiaOAuthToken[] = "oauthToken";
-extern const char kGaiaOAuthSecret[] = "oauthSecret";
-extern const char kGaiaOAuthDuration[] = "3600";
+const char kGaiaOAuthToken[] = "oauthToken";
+const char kGaiaOAuthSecret[] = "oauthSecret";
+const char kGaiaOAuthDuration[] = "3600";
+const char kGaiaOAuth2LoginRefreshToken[] = "oauth2LoginRefreshToken";
+const char kGaiaOAuth2LoginAccessToken[] = "oauth2LoginAccessToken";
 
 }  // namespace GaiaConstants