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

chromeos/login/auth/login_performer.cc

 // 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.
 
 #include "chromeos/login/auth/login_performer.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
@@ skipping 210 matching lines @@
                                     user_context));
 }
 
 void LoginPerformer::LoginOffTheRecord() {
   EnsureAuthenticator();
   task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&Authenticator::LoginOffTheRecord, authenticator_.get()));
 }
 
-void LoginPerformer::LoginAsKioskAccount(const std::string& app_user_id,
+void LoginPerformer::LoginAsKioskAccount(const AccountId& app_account_id,
                                          bool use_guest_mount) {
   EnsureAuthenticator();
-  task_runner_->PostTask(FROM_HERE,
-                         base::Bind(&Authenticator::LoginAsKioskAccount,
-                                    authenticator_.get(),
-                                    app_user_id,
-                                    use_guest_mount));
+  task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&Authenticator::LoginAsKioskAccount, authenticator_.get(),
+                 app_account_id, use_guest_mount));
 }
 
 void LoginPerformer::RecoverEncryptedData(const std::string& old_password) {
   task_runner_->PostTask(FROM_HERE,
                          base::Bind(&Authenticator::RecoverEncryptedData,
                                     authenticator_.get(),
                                     old_password));
 }
 
 void LoginPerformer::ResyncEncryptedData() {
@@ skipping 38 matching lines @@
   } else {
     NOTREACHED();
   }
   user_context_.ClearSecrets();
 }
 
 void LoginPerformer::EnsureAuthenticator() {
   authenticator_ = CreateAuthenticator();
 }
 }  // namespace chromeos