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

chrome/browser/chromeos/policy/device_local_account_policy_store.cc

 // Copyright (c) 2012 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 "chrome/browser/chromeos/policy/device_local_account_policy_store.h"
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/chromeos/policy/browser_policy_connector_chromeos.h"
@@ skipping 132 matching lines @@
       device_settings_service_->GetPublicKey();
   if (!key.get() || !key->is_loaded() || !device_policy_data) {
     status_ = CloudPolicyStore::STATUS_BAD_STATE;
     NotifyStoreLoaded();
     return;
   }
 
   scoped_ptr<UserCloudPolicyValidator> validator(
       UserCloudPolicyValidator::Create(policy_response.Pass(),
                                        background_task_runner()));
-  validator->ValidateUsername(account_id_, false);
+  validator->ValidateUsername(user_manager::UserID::FromUserEmail(account_id_), false);
   validator->ValidatePolicyType(dm_protocol::kChromePublicAccountPolicyType);
   // The timestamp is verified when storing a new policy downloaded from the
   // server but not when loading a cached policy from disk.
   // See SessionManagerOperation::ValidateDeviceSettings for the rationale.
   validator->ValidateAgainstCurrentPolicy(
       policy(),
       valid_timestamp_required
           ? CloudPolicyValidatorBase::TIMESTAMP_REQUIRED
           : CloudPolicyValidatorBase::TIMESTAMP_NOT_REQUIRED,
       CloudPolicyValidatorBase::DM_TOKEN_NOT_REQUIRED);
 
   // Validate the DMToken to match what device policy has.
   validator->ValidateDMToken(device_policy_data->request_token(),
                              CloudPolicyValidatorBase::DM_TOKEN_REQUIRED);
 
   validator->ValidatePayload();
   policy::BrowserPolicyConnectorChromeOS* connector =
       g_browser_process->platform_part()->browser_policy_connector_chromeos();
   validator->ValidateSignature(key->as_string(),
                                GetPolicyVerificationKey(),
                                connector->GetEnterpriseDomain(),
                                false);
   validator.release()->StartValidation(callback);
 }
 
 }  // namespace policy