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

chromeos/login/auth/stub_authenticator.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/stub_authenticator.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/thread_task_runner_handle.h"
@@ skipping 57 matching lines @@
 
 void StubAuthenticator::LoginAsPublicSession(const UserContext& user_context) {
   UserContext logged_in_user_context = user_context;
   logged_in_user_context.SetIsUsingOAuth(false);
   logged_in_user_context.SetUserIDHash(
       logged_in_user_context.GetAccountId().GetUserEmail() + kUserIdHashSuffix);
   consumer_->OnAuthSuccess(logged_in_user_context);
 }
 
 void StubAuthenticator::LoginAsKioskAccount(
-    const std::string& /* app_user_id */,
+    const AccountId& /* app_account_id */,
     bool use_guest_mount) {
   UserContext user_context(expected_user_context_.GetAccountId());
   user_context.SetIsUsingOAuth(false);
   user_context.SetUserIDHash(
       expected_user_context_.GetAccountId().GetUserEmail() + kUserIdHashSuffix);
   consumer_->OnAuthSuccess(user_context);
 }
 
 void StubAuthenticator::OnAuthSuccess() {
   // If we want to be more like the real thing, we could save the user ID
@@ skipping 16 matching lines @@
 
 void StubAuthenticator::SetExpectedCredentials(
     const UserContext& user_context) {
   expected_user_context_ = user_context;
 }
 
 StubAuthenticator::~StubAuthenticator() {
 }
 
 }  // namespace chromeos