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

chrome/browser/chromeos/login/session/user_session_manager.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 CHROME_BROWSER_CHROMEOS_LOGIN_SESSION_USER_SESSION_MANAGER_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_SESSION_USER_SESSION_MANAGER_H_
 
 #include <string>
 
 #include "base/callback.h"
@@ skipping 415 matching lines @@
 
   // True if user sessions has been restored after crash.
   // On a normal boot then login into user sessions this will be false.
   bool user_sessions_restored_;
 
   // True if user sessions restoration after crash is in progress.
   bool user_sessions_restore_in_progress_;
 
   // User sessions that have to be restored after browser crash.
   // [user_id] > [user_id_hash]
-  SessionManagerClient::ActiveSessionsMap pending_user_sessions_;
+  using PendingUserSessions = std::map<AccountId, std::string>;
+
+  PendingUserSessions pending_user_sessions_;
 
   base::ObserverList<chromeos::UserSessionStateObserver>
       session_state_observer_list_;
 
   // OAuth2 session related members.
 
   // True if we should restart chrome right after session restore.
   bool exit_after_session_restore_;
 
   // Sesion restore strategy.
@@ skipping 30 matching lines @@
   bool waiting_for_child_account_status_;
 
   base::WeakPtrFactory<UserSessionManager> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(UserSessionManager);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_SESSION_USER_SESSION_MANAGER_H_