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

chrome/browser/supervised_user/child_accounts/child_account_service.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/supervised_user/child_accounts/child_account_service.h"
 
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/field_trial.h"
@@ skipping 85 matching lines @@
 void ChildAccountService::RegisterProfilePrefs(
     user_prefs::PrefRegistrySyncable* registry) {
   registry->RegisterBooleanPref(prefs::kChildAccountStatusKnown, false);
 }
 
 void ChildAccountService::SetIsChildAccount(bool is_child_account) {
   PropagateChildStatusToUser(is_child_account);
   if (profile_->IsChild() != is_child_account) {
     if (is_child_account) {
       profile_->GetPrefs()->SetString(prefs::kSupervisedUserId,
-                                      supervised_users::kChildAccountSUID);
+                                      supervised_users::GetChildAccountSUID().GetUserEmail());
     } else {
       profile_->GetPrefs()->ClearPref(prefs::kSupervisedUserId);
     }
   }
   profile_->GetPrefs()->SetBoolean(prefs::kChildAccountStatusKnown, true);
 
   for (const auto& callback : status_received_callback_list_)
     callback.Run();
   status_received_callback_list_.clear();
 }
@@ skipping 265 matching lines @@
 }
 
 void ChildAccountService::ClearSecondCustodianPrefs() {
   profile_->GetPrefs()->ClearPref(prefs::kSupervisedUserSecondCustodianName);
   profile_->GetPrefs()->ClearPref(prefs::kSupervisedUserSecondCustodianEmail);
   profile_->GetPrefs()->ClearPref(
       prefs::kSupervisedUserSecondCustodianProfileURL);
   profile_->GetPrefs()->ClearPref(
       prefs::kSupervisedUserSecondCustodianProfileImageURL);
 }