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

chromeos/cryptohome/homedir_methods.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_CRYPTOHOME_HOMEDIR_METHODS_H_
 #define CHROMEOS_CRYPTOHOME_HOMEDIR_METHODS_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 71 matching lines @@
                            const std::string& signature,
                            const Callback& callback) = 0;
 
   // Asks cryptohomed to remove specific key labeled with |label| for user
   // identified by |id| using |auth|.
   virtual void RemoveKeyEx(const Identification& id,
                            const Authorization& auth,
                            const std::string& label,
                            const Callback& callback) = 0;
 
+  // Asks cryptohomed to change cryptohome identification |id_from| to |id_to|,
+  // which results in cryptohome directory renaming.
+  virtual void RenameCryptohome(const Identification& id_from,
+                                const Identification& id_to,
+                                const Callback& callback) = 0;
+
   // Creates the global HomedirMethods instance.
   static void Initialize();
 
   // Similar to Initialize(), but can inject an alternative
   // HomedirMethods such as MockHomedirMethods for testing.
   // The injected object will be owned by the internal pointer and deleted
   // by Shutdown().
   static void InitializeForTesting(HomedirMethods* homedir_methods);
 
   // Destroys the global HomedirMethods instance if it exists.
   static void Shutdown();
 
   // Returns a pointer to the global HomedirMethods instance.
   // Initialize() should already have been called.
   static HomedirMethods* GetInstance();
 };
 
 }  // namespace cryptohome
 
 #endif  // CHROMEOS_CRYPTOHOME_HOMEDIR_METHODS_H_