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

chrome/browser/profiles/profile_window.cc

 // Copyright 2013 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/profiles/profile_window.h"
 
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/prefs/pref_service.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 270 matching lines @@
                                    path);
   g_browser_process->profile_manager()->CreateProfileAsync(
       path,
       base::Bind(&OpenBrowserWindowForProfile,
                  callback,
                  always_create,
                  false,
                  desktop_type),
       base::string16(),
       base::string16(),
-      std::string());
+      user_manager::UserID(std::string(), std::string()));

[Denis Kuznetsov (DE-MUC), 2015/06/10 16:50:47]

EmptyUserID

 }
 
 void SwitchToGuestProfile(chrome::HostDesktopType desktop_type,
                           ProfileManager::CreateCallback callback) {
   const base::FilePath& path = ProfileManager::GetGuestProfilePath();
   ProfileMetrics::LogProfileSwitch(ProfileMetrics::SWITCH_PROFILE_GUEST,
                                    g_browser_process->profile_manager(),
                                    path);
   g_browser_process->profile_manager()->CreateProfileAsync(
       path,
       base::Bind(&OpenBrowserWindowForProfile,
                  callback,
                  false,
                  false,
                  desktop_type),
       base::string16(),
       base::string16(),
-      std::string());
+      user_manager::UserID(std::string(), std::string()));
 }
 
 bool HasProfileSwitchTargets(Profile* profile) {
   size_t min_profiles = profile->IsGuestSession() ? 1 : 2;
   size_t number_of_profiles =
       g_browser_process->profile_manager()->GetNumberOfProfiles();
   return number_of_profiles >= min_profiles;
 }
 
 void CreateAndSwitchToNewProfile(chrome::HostDesktopType desktop_type,
                                  ProfileManager::CreateCallback callback,
                                  ProfileMetrics::ProfileAdd metric) {
   ProfileInfoCache& cache =
       g_browser_process->profile_manager()->GetProfileInfoCache();
 
   int placeholder_avatar_index = profiles::GetPlaceholderAvatarIndex();
   ProfileManager::CreateMultiProfileAsync(
       cache.ChooseNameForNewProfile(placeholder_avatar_index),
       base::UTF8ToUTF16(profiles::GetDefaultAvatarIconUrl(
           placeholder_avatar_index)),
       base::Bind(&OpenBrowserWindowForProfile,
                  callback,
                  true,
                  true,
                  desktop_type),
-      std::string());
+      user_manager::UserID(std::string(), std::string()));
   ProfileMetrics::LogProfileAddNewUser(metric);
 }
 
 void GuestBrowserCloseSuccess(const base::FilePath& profile_path) {
   UserManager::Show(base::FilePath(),
                     profiles::USER_MANAGER_NO_TUTORIAL,
                     profiles::USER_MANAGER_SELECT_PROFILE_NO_ACTION);
 }
 
 void CloseGuestProfileWindows() {
@@ skipping 77 matching lines @@
   // from the system profile.
   g_browser_process->profile_manager()->CreateProfileAsync(
       ProfileManager::GetSystemProfilePath(),
       base::Bind(&OnUserManagerSystemProfileCreated,
                  profile_path_to_focus,
                  tutorial_mode,
                  profile_open_action,
                  callback),
       base::string16(),
       base::string16(),
-      std::string());
+      user_manager::UserID(std::string(), std::string()));
 }
 
 void ShowUserManagerMaybeWithTutorial(Profile* profile) {
   // Guest users cannot appear in the User Manager, nor display a tutorial.
   if (!profile || profile->IsGuestSession()) {
     UserManager::Show(base::FilePath(),
                       profiles::USER_MANAGER_NO_TUTORIAL,
                       profiles::USER_MANAGER_SELECT_PROFILE_NO_ACTION);
     return;
   }
@@ skipping 98 matching lines @@
   PrefService* local_state = g_browser_process->local_state();
   const bool dismissed = local_state->GetBoolean(
       prefs::kProfileAvatarRightClickTutorialDismissed);
 
   // Don't show the tutorial if it's already been dismissed or if right-clicking
   // wouldn't show any targets.
   return !dismissed && HasProfileSwitchTargets(profile);
 }
 
 }  // namespace profiles