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

chrome/browser/chromeos/login/easy_unlock/easy_unlock_key_manager.cc

 // 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.
 
 #include "chrome/browser/chromeos/login/easy_unlock/easy_unlock_key_manager.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/stringprintf.h"
@@ skipping 89 matching lines @@
     const UserContext& user_context,
     const GetDeviceDataListCallback& callback) {
   read_operation_queue_.push_back(new EasyUnlockGetKeysOperation(
       user_context, base::Bind(&EasyUnlockKeyManager::OnKeysFetched,
                                weak_ptr_factory_.GetWeakPtr(), callback)));
   RunNextOperation();
 }
 
 // static
 void EasyUnlockKeyManager::DeviceDataToRemoteDeviceDictionary(
-    const std::string& user_id,
+    const user_manager::UserID& user_id,
     const EasyUnlockDeviceKeyData& data,
     base::DictionaryValue* dict) {
   dict->SetString(kKeyBluetoothAddress, data.bluetooth_address);
   dict->SetString(kKeyPsk, data.psk);
   scoped_ptr<base::DictionaryValue> permit_record(new base::DictionaryValue);
   dict->Set(kKeyPermitRecord, permit_record.release());
   dict->SetString(kKeyPermitId, data.public_key);
   dict->SetString(kKeyPermitData, data.public_key);
   dict->SetString(kKeyPermitType, kPermitTypeLicence);
   dict->SetString(kKeyPermitPermitId,
                   base::StringPrintf(kPermitPermitIdFormat,
-                                     user_id.c_str()));
+                                     user_id.GetUserEmail().c_str()));
 }
 
 // static
 bool EasyUnlockKeyManager::RemoteDeviceDictionaryToDeviceData(
     const base::DictionaryValue& dict,
     EasyUnlockDeviceKeyData* data) {
   std::string bluetooth_address;
   std::string public_key;
   std::string psk;
 
   if (!dict.GetString(kKeyBluetoothAddress, &bluetooth_address) ||
       !dict.GetString(kKeyPermitId, &public_key) ||
       !dict.GetString(kKeyPsk, &psk)) {
     return false;
   }
 
   data->bluetooth_address.swap(bluetooth_address);
   data->public_key.swap(public_key);
   data->psk.swap(psk);
   return true;
 }
 
 // static
 void EasyUnlockKeyManager::DeviceDataListToRemoteDeviceList(
-    const std::string& user_id,
+    const user_manager::UserID& user_id,
     const EasyUnlockDeviceKeyDataList& data_list,
     base::ListValue* device_list) {
   device_list->Clear();
   for (size_t i = 0; i < data_list.size(); ++i) {
     scoped_ptr<base::DictionaryValue> device_dict(new base::DictionaryValue);
     DeviceDataToRemoteDeviceDictionary(
         user_id, data_list[i], device_dict.get());
     device_list->Append(device_dict.release());
   }
 }
@@ skipping 57 matching lines @@
     const EasyUnlockDeviceKeyDataList& fetched_data) {
   if (!callback.is_null())
     callback.Run(fetch_success, fetched_data);
 
   DCHECK(pending_read_operation_);
   pending_read_operation_.reset();
   RunNextOperation();
 }
 
 }  // namespace chromeos