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

chromeos/cryptohome/homedir_methods.cc

Index: chromeos/cryptohome/homedir_methods.cc
diff --git a/chromeos/cryptohome/homedir_methods.cc b/chromeos/cryptohome/homedir_methods.cc
index 8413c72f239dbdc35a33339c00e342cbd733b279..3e3defb486da8be8f36c6b859b731b55a9c42523 100644
--- a/chromeos/cryptohome/homedir_methods.cc
+++ b/chromeos/cryptohome/homedir_methods.cc
@@ -98,7 +98,7 @@ void FillKeyProtobuf(const KeyDefinition& key_def, Key* key) {
 // Fill identification protobuffer.
 void FillIdentificationProtobuf(const Identification& id,
                                 cryptohome::AccountIdentifier* id_proto) {
-  id_proto->set_email(id.user_id);
+  id_proto->set_account_id(id.id());
 }
 
 // Fill authorization protobuffer.
@@ -306,12 +306,24 @@ class HomedirMethodsImpl : public HomedirMethods {
     pb_update_key.set_authorization_signature(signature);
 
     DBusThreadManager::Get()->GetCryptohomeClient()->UpdateKeyEx(
-        id_proto,
-        auth_proto,
-        pb_update_key,
+        id_proto, auth_proto, pb_update_key,
         base::Bind(&HomedirMethodsImpl::OnBaseReplyCallback,
-                   weak_ptr_factory_.GetWeakPtr(),
-                   callback));
+                   weak_ptr_factory_.GetWeakPtr(), callback));
+  }
+
+  void RenameCryptohome(const Identification& id_from,
+                        const Identification& id_to,
+                        const Callback& callback) override {
+    cryptohome::AccountIdentifier id_from_proto;
+    cryptohome::AccountIdentifier id_to_proto;
+
+    FillIdentificationProtobuf(id_from, &id_from_proto);
+    FillIdentificationProtobuf(id_to, &id_to_proto);
+
+    DBusThreadManager::Get()->GetCryptohomeClient()->RenameCryptohome(
+        id_from_proto, id_to_proto,
+        base::Bind(&HomedirMethodsImpl::OnBaseReplyCallback,
+                   weak_ptr_factory_.GetWeakPtr(), callback));
   }
 
  private: