We should use UserID object to identify users instead of username.

chrome/browser/chromeos/ownership/owner_settings_service_chromeos.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_OWNERSHIP_OWNER_SETTINGS_SERVICE_CHROMEOS_H_
 #define CHROME_BROWSER_CHROMEOS_OWNERSHIP_OWNER_SETTINGS_SERVICE_CHROMEOS_H_
 
 #include <string>
 #include <vector>
 
 #include "base/callback_forward.h"
 #include "base/containers/scoped_ptr_hash_map.h"
 #include "base/macros.h"
 #include "base/values.h"
 #include "chrome/browser/chromeos/policy/proto/chrome_device_policy.pb.h"
 #include "chrome/browser/chromeos/settings/device_settings_service.h"
 #include "chromeos/dbus/session_manager_client.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "components/ownership/owner_key_util.h"
 #include "components/ownership/owner_settings_service.h"
 #include "components/policy/core/common/cloud/cloud_policy_constants.h"
+#include "components/user_manager/user_id.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
 class Profile;
 
 namespace content {
 class WebUI;
 }
 
 namespace ownership {
@@ skipping 66 matching lines @@
   // Checks if the user is the device owner, without the user profile having to
   // been initialized. Should be used only if login state is in safe mode.
   static void IsOwnerForSafeModeAsync(
       const std::string& user_hash,
       const scoped_refptr<ownership::OwnerKeyUtil>& owner_key_util,
       const IsOwnerCallback& callback);
 
   // Assembles PolicyData based on |settings|, |policy_data|, |user_id| and
   // |pending_management_settings|. Applies local-owner policy fixups if needed.
   static scoped_ptr<enterprise_management::PolicyData> AssemblePolicy(
-      const std::string& user_id,
+      const user_manager::UserID& user_id,
       const enterprise_management::PolicyData* policy_data,
       bool apply_pending_mangement_settings,
       const ManagementSettings& pending_management_settings,
       enterprise_management::ChromeDeviceSettingsProto* settings);
 
   // Updates device |settings|.
   static void UpdateDeviceSettings(
       const std::string& path,
       const base::Value& value,
       enterprise_management::ChromeDeviceSettingsProto& settings);
 
  protected:
   OwnerSettingsServiceChromeOS(
       DeviceSettingsService* device_settings_service,
       Profile* profile,
       const scoped_refptr<ownership::OwnerKeyUtil>& owner_key_util);
 
  private:
   friend class OwnerSettingsServiceChromeOSFactory;
 
   // Perform fixups required to ensure sensical local-owner device policy:
   //  1) user whitelisting must be explicitly allowed or disallowed, and
   //  2) the owner user must be on the whitelist, if it's enforced.
   static void FixupLocalOwnerPolicy(
-      const std::string& user_id,
+      const user_manager::UserID& user_id,
       enterprise_management::ChromeDeviceSettingsProto* settings);
 
   // OwnerSettingsService protected interface overrides:
 
   // Reloads private key from profile's NSS slots, responds via |callback|. On
   // success, |private_key| is non-null, but if the private key doesn't exist,
   // |private_key->key()| may be null.
   void ReloadKeypairImpl(const base::Callback<
       void(const scoped_refptr<ownership::PublicKey>& public_key,
            const scoped_refptr<ownership::PrivateKey>& private_key)>& callback)
@@ skipping 17 matching lines @@
   // Report status to observers and tries to continue storing pending chages to
   // device settings.
   void ReportStatusAndContinueStoring(bool success);
 
   DeviceSettingsService* device_settings_service_;
 
   // Profile this service instance belongs to.
   Profile* profile_;
 
   // User ID this service instance belongs to.
-  std::string user_id_;
+  user_manager::UserID user_id_;
 
   // Whether profile still needs to be initialized.
   bool waiting_for_profile_creation_;
 
   // Whether TPM token still needs to be initialized.
   bool waiting_for_tpm_token_;
 
   // True if local-owner policy fixups are still pending.
   bool has_pending_fixups_;
 
@@ skipping 20 matching lines @@
   base::WeakPtrFactory<OwnerSettingsServiceChromeOS> weak_factory_;
 
   base::WeakPtrFactory<OwnerSettingsServiceChromeOS> store_settings_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(OwnerSettingsServiceChromeOS);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_OWNERSHIP_OWNER_SETTINGS_SERVICE_CHROMEOS_H_