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

chrome/browser/ui/browser_finder.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_finder.h"
 
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser_iterator.h"
 #include "chrome/browser/ui/browser_list.h"
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/browser/ui/tab_contents/tab_contents_iterator.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
+#include "components/user_manager/user_id.h"
 #include "content/public/browser/navigation_controller.h"
 
 #if defined(OS_CHROMEOS)
 #include "chrome/browser/ui/ash/multi_user/multi_user_util.h"
 #include "chrome/browser/ui/ash/multi_user/multi_user_window_manager.h"
 #endif
 
 using content::WebContents;
 
 namespace {
@@ skipping 24 matching lines @@
     return false;
   }
 
   bool matches_profile = browser->profile() == profile;
 #if defined(OS_CHROMEOS)
   // Get the profile on which the window is currently shown.
   // MultiUserWindowManager might be NULL under test scenario.
   chrome::MultiUserWindowManager* const window_manager =
       chrome::MultiUserWindowManager::GetInstance();
   if (window_manager) {
-    const std::string& shown_user_id = window_manager->GetUserPresentingWindow(
+    const user_manager::UserID& shown_user_id = window_manager->GetUserPresentingWindow(
         browser->window()->GetNativeWindow());
     Profile* shown_profile =
         shown_user_id.empty()
             ? nullptr
             : multi_user_util::GetProfileFromUserID(shown_user_id);
     matches_profile &= !shown_profile || shown_profile == profile;
   }
 #endif
 
   if (match_types & kMatchOriginalProfile) {
@@ skipping 156 matching lines @@
 
 size_t GetBrowserCount(Profile* profile, HostDesktopType type) {
   return GetBrowserCountImpl(profile, type, kMatchAny);
 }
 
 size_t GetTabbedBrowserCount(Profile* profile, HostDesktopType type) {
   return GetBrowserCountImpl(profile, type, kMatchTabbed);
 }
 
 }  // namespace chrome