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

chrome/browser/ui/browser_navigator.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/ui/browser_navigator.h"
 
 #include <algorithm>
 
 #include "base/command_line.h"
 #include "base/prefs/pref_service.h"
@@ skipping 11 matching lines @@
 #include "chrome/browser/ui/browser_instant_controller.h"
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/browser/ui/host_desktop.h"
 #include "chrome/browser/ui/location_bar/location_bar.h"
 #include "chrome/browser/ui/search/instant_search_prerenderer.h"
 #include "chrome/browser/ui/singleton_tabs.h"
 #include "chrome/browser/ui/status_bubble.h"
 #include "chrome/browser/ui/tab_helpers.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/common/url_constants.h"
+#include "components/user_manager/user_id.h"
 #include "content/public/browser/browser_url_handler.h"
 #include "content/public/browser/navigation_entry.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/web_contents.h"
 
 #if defined(USE_ASH)
 #include "chrome/browser/ui/ash/multi_user/multi_user_window_manager.h"
 #endif
 
@@ skipping 491 matching lines @@
 #if defined(USE_ASH)
   if (source_browser && source_browser != params->browser) {
     // When the newly created browser was spawned by a browser which visits
     // another user's desktop, it should be shown on the same desktop as the
     // originating one. (This is part of the desktop separation per profile).
     MultiUserWindowManager* manager = MultiUserWindowManager::GetInstance();
     // Some unit tests have no manager instantiated.
     if (manager) {
       aura::Window* src_window = source_browser->window()->GetNativeWindow();
       aura::Window* new_window = params->browser->window()->GetNativeWindow();
-      const std::string& src_user =
+      const user_manager::UserID& src_user =
           manager->GetUserPresentingWindow(src_window);
       if (src_user != manager->GetUserPresentingWindow(new_window)) {
         // Once the window gets presented, it should be shown on the same
         // desktop as the desktop of the creating browser. Note that this
         // command will not show the window if it wasn't shown yet by the
         // browser creation.
         manager->ShowWindowForUser(new_window, src_user);
       }
     }
   }
@@ skipping 197 matching lines @@
   bool reverse_on_redirect = false;
   content::BrowserURLHandler::GetInstance()->RewriteURLIfNecessary(
       &rewritten_url, browser_context, &reverse_on_redirect);
 
   // Some URLs are mapped to uber subpages. Do not allow them in incognito.
   return !(rewritten_url.scheme() == content::kChromeUIScheme &&
            rewritten_url.host() == chrome::kChromeUIUberHost);
 }
 
 }  // namespace chrome