ChromeOS cryptohome should be able to use gaia id as user identifier.

chromeos/login/auth/login_performer.h

 // Copyright 2014 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 CHROMEOS_LOGIN_AUTH_LOGIN_PERFORMER_H_
 #define CHROMEOS_LOGIN_AUTH_LOGIN_PERFORMER_H_
 
 #include <string>
 
 #include "base/callback.h"
@@ skipping 61 matching lines @@
 
   // Performs supervised user login with a given |user_context|.
   void LoginAsSupervisedUser(const UserContext& user_context);
 
   // Performs actions to prepare guest mode login.
   void LoginOffTheRecord();
 
   // Performs public session login with a given |user_context|.
   void LoginAsPublicSession(const UserContext& user_context);
 
-  // Performs a login into the kiosk mode account with |app_user_id|.
-  void LoginAsKioskAccount(const std::string& app_user_id,
+  // Performs a login into the kiosk mode account with |app_account_id|.
+  void LoginAsKioskAccount(const AccountId& app_account_id,
                            bool use_guest_mount);
 
   // AuthStatusConsumer implementation:
   void OnAuthFailure(const AuthFailure& error) override;
   void OnAuthSuccess(const UserContext& user_context) override;
   void OnOffTheRecordAuthSuccess() override;
   void OnPasswordChangeDetected() override;
 
   // Migrates cryptohome using |old_password| specified.
   void RecoverEncryptedData(const std::string& old_password);
@@ skipping 126 matching lines @@
   // Authorization mode type.
   AuthorizationMode auth_mode_;
 
   base::WeakPtrFactory<LoginPerformer> weak_factory_;
   DISALLOW_COPY_AND_ASSIGN(LoginPerformer);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_LOGIN_AUTH_LOGIN_PERFORMER_H_