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

components/proximity_auth/screenlock_bridge.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 "components/proximity_auth/screenlock_bridge.h"
 
 #include "base/logging.h"
 #include "base/strings/string16.h"
 #include "components/proximity_auth/proximity_auth_client.h"
+#include "components/user_manager/user_id.h"
 
 #if defined(OS_CHROMEOS)
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "chromeos/dbus/session_manager_client.h"
 #endif
 
 namespace proximity_auth {
 namespace {
 
 // Ids for the icons that are supported by lock screen and signin screen
@@ skipping 23 matching lines @@
     case ScreenlockBridge::USER_POD_CUSTOM_ICON_SPINNER:
       return kSpinnerUserPodCustomIconId;
     default:
       return "";
   }
 }
 
 }  // namespace
 
 ScreenlockBridge::ScreenlockBridge(ProximityAuthClient* client)
-    : client_(client), lock_handler_(nullptr) {
+    : client_(client), lock_handler_(nullptr), focused_user_id_(std::string(), std::string()) {
   DCHECK(client_);
 }
 
 ScreenlockBridge::~ScreenlockBridge() {
 }
 
 ScreenlockBridge::UserPodCustomIconOptions::UserPodCustomIconOptions()
     : autoshow_tooltip_(false),
       hardlock_on_click_(false),
       is_trial_run_(false) {
@@ skipping 68 matching lines @@
   else
     screen_type = lock_handler->GetScreenType();
 
   lock_handler_ = lock_handler;
   if (lock_handler_)
     FOR_EACH_OBSERVER(Observer, observers_, OnScreenDidLock(screen_type));
   else
     FOR_EACH_OBSERVER(Observer, observers_, OnScreenDidUnlock(screen_type));
 }
 
-void ScreenlockBridge::SetFocusedUser(const std::string& user_id) {
+void ScreenlockBridge::SetFocusedUser(const user_manager::UserID& user_id) {
   if (user_id == focused_user_id_)
     return;
   focused_user_id_ = user_id;
   FOR_EACH_OBSERVER(Observer, observers_, OnFocusedUserChanged(user_id));
 }
 
 bool ScreenlockBridge::IsLocked() const {
   return lock_handler_ != nullptr;
 }
 
 void ScreenlockBridge::Lock(content::BrowserContext* browser_context) {
 #if defined(OS_CHROMEOS)
   chromeos::SessionManagerClient* session_manager =
       chromeos::DBusThreadManager::Get()->GetSessionManagerClient();
   session_manager->RequestLockScreen();
 #else
   client_->Lock(browser_context);
 #endif
 }
 
 void ScreenlockBridge::Unlock(content::BrowserContext* browser_context) {
-  if (lock_handler_)
-    lock_handler_->Unlock(client_->GetAuthenticatedUsername(browser_context));
+  if (lock_handler_) {
+    const user_manager::UserID user_id(user_manager::UserID::FromUserEmail(client_->GetAuthenticatedUsername(browser_context)));
+    lock_handler_->Unlock(user_id);
+  }
 }
 
 void ScreenlockBridge::AddObserver(Observer* observer) {
   observers_.AddObserver(observer);
 }
 
 void ScreenlockBridge::RemoveObserver(Observer* observer) {
   observers_.RemoveObserver(observer);
 }
 
 }  // namespace proximity_auth