When a user logs into sync, the appropriate cookies are retrieved so that

chrome/browser/chromeos/login/issue_response_handler.h

 // 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.
 
 #ifndef CHROME_BROWSER_CHROMEOS_LOGIN_ISSUE_RESPONSE_HANDLER_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_ISSUE_RESPONSE_HANDLER_H_
 #pragma once
 
 #include <string>
 
@@ skipping 24 matching lines @@
   // Takes in a response from IssueAuthToken, formats into an appropriate query
   // to sent to TokenAuth, and issues said query.  |catcher| will receive
   // the response to the fetch.  This fetch will follow redirects, which is
   // necesary to support GAFYD and corp accounts.
   virtual URLFetcher* Handle(const std::string& to_process,
                              URLFetcher::Delegate* catcher);
 
   // exposed for testing
   std::string token_url() { return token_url_; }
 
+  // Builds a TokenAuth URL using the specified authorization token.
+  static std::string BuildTokenAuthUrlWithToken(const std::string& token);
+
  private:
   std::string token_url_;
   net::URLRequestContextGetter* getter_;
   DISALLOW_COPY_AND_ASSIGN(IssueResponseHandler);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_ISSUE_RESPONSE_HANDLER_H_