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

chrome/browser/sync/signin_manager.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.
 //
 // The signin manager encapsulates some functionality tracking
 // which user is signed in. When a user is signed in, a ClientLogin
 // request is run on their behalf. Auth tokens are fetched from Google
 // and the results are stored in the TokenService.
 
 #ifndef CHROME_BROWSER_SYNC_SIGNIN_MANAGER_H_
 #define CHROME_BROWSER_SYNC_SIGNIN_MANAGER_H_
 #pragma once
 
 #include <string>
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "chrome/common/net/gaia/gaia_auth_consumer.h"
 #include "chrome/common/net/gaia/google_service_auth_error.h"
+#include "content/common/notification_observer.h"
+#include "content/common/notification_registrar.h"
 
 class GaiaAuthFetcher;
 class Profile;
 class PrefService;
 
 // Details for the Notification type GOOGLE_SIGNIN_SUCCESSFUL.
 // A listener might use this to make note of a username / password
 // pair for encryption keys.
 struct GoogleServiceSigninSuccessDetails {
   GoogleServiceSigninSuccessDetails(const std::string& in_username,
                                     const std::string& in_password)
       : username(in_username),
         password(in_password) {}
   std::string username;
   std::string password;
 };
 
-class SigninManager : public GaiaAuthConsumer {
+class SigninManager : public GaiaAuthConsumer , public NotificationObserver {
  public:
   SigninManager();
   virtual ~SigninManager();
 
   // Call to register our prefs.
   static void RegisterUserPrefs(PrefService* user_prefs);
 
   // If user was signed in, load tokens from DB if available.
   void Initialize(Profile* profile);
 
@@ skipping 21 matching lines @@
   void SignOut();
 
   // GaiaAuthConsumer
   virtual void OnClientLoginSuccess(const ClientLoginResult& result);
   virtual void OnClientLoginFailure(const GoogleServiceAuthError& error);
   virtual void OnGetUserInfoSuccess(const std::string& key,
                                     const std::string& value);
   virtual void OnGetUserInfoKeyNotFound(const std::string& key);
   virtual void OnGetUserInfoFailure(const GoogleServiceAuthError& error);
 
+  // NotificationObserver
+  virtual void Observe(NotificationType type,
+                       const NotificationSource& source,
+                       const NotificationDetails& details) OVERRIDE;
+
  private:
   Profile* profile_;
   std::string username_;
   std::string password_;  // This is kept empty whenever possible.
   bool had_two_factor_error_;
 
   // Result of the last client login, kept pending the lookup of the
   // canonical email.
   ClientLoginResult last_result_;
 
   // Actual client login handler.
   scoped_ptr<GaiaAuthFetcher> client_login_;
+
+  // Register for notifications from the TokenService.
+  NotificationRegistrar registrar_;
+
+  DISALLOW_COPY_AND_ASSIGN(SigninManager);
 };
 
 #endif  // CHROME_BROWSER_SYNC_SIGNIN_MANAGER_H_