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

chrome/browser/profiles/profile_impl.cc

Index: chrome/browser/profiles/profile_impl.cc
diff --git a/chrome/browser/profiles/profile_impl.cc b/chrome/browser/profiles/profile_impl.cc
index 6eb96e9124b0403f2162ae6a12ebe790e1d9cee6..c6c8c6ed6659e33402ec48756fb45d4fa5c99f88 100644
--- a/chrome/browser/profiles/profile_impl.cc
+++ b/chrome/browser/profiles/profile_impl.cc
@@ -777,8 +777,8 @@ bool ProfileImpl::IsSupervised() {
 
 bool ProfileImpl::IsChild() {
 #if defined(ENABLE_SUPERVISED_USERS)
-  return GetPrefs()->GetString(prefs::kSupervisedUserId) ==
-      supervised_users::kChildAccountSUID;
+  return user_manager::UserID::FromUserEmail(GetPrefs()->GetString(prefs::kSupervisedUserId)) ==
+      supervised_users::GetChildAccountSUID();
 #else
   return false;
 #endif
@@ -1159,8 +1159,8 @@ void ProfileImpl::ChangeAppLocale(
   if (via != APP_LOCALE_CHANGED_VIA_PUBLIC_SESSION_LOGIN)
     local_state->SetString(prefs::kApplicationLocale, new_locale);
 
-  if (user_manager::UserManager::Get()->GetOwnerEmail() ==
-      chromeos::ProfileHelper::Get()->GetUserByProfile(this)->email())
+  if (user_manager::UserManager::Get()->GetOwnerID() ==
+      chromeos::ProfileHelper::Get()->GetUserByProfile(this)->GetUserID())
     local_state->SetString(prefs::kOwnerLocale, new_locale);
 }
 
@@ -1231,8 +1231,8 @@ void ProfileImpl::UpdateProfileSupervisedUserIdCache() {
   ProfileInfoCache& cache = profile_manager->GetProfileInfoCache();
   size_t index = cache.GetIndexOfProfileWithPath(GetPath());
   if (index != std::string::npos) {
-    std::string supervised_user_id =
-        GetPrefs()->GetString(prefs::kSupervisedUserId);
+    const user_manager::UserID supervised_user_id(
+        user_manager::UserID::FromUserEmail(GetPrefs()->GetString(prefs::kSupervisedUserId)));
     cache.SetSupervisedUserIdOfProfileAtIndex(index, supervised_user_id);
     ProfileMetrics::UpdateReportedProfilesStatistics(profile_manager);
   }