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

chrome/browser/chromeos/policy/device_local_account.cc

Index: chrome/browser/chromeos/policy/device_local_account.cc
diff --git a/chrome/browser/chromeos/policy/device_local_account.cc b/chrome/browser/chromeos/policy/device_local_account.cc
index 63c7a14778f00948bb286a471db6b78e375ad8d6..eb4e45feabd3b7e51aa1389a7f27be7a24583338 100644
--- a/chrome/browser/chromeos/policy/device_local_account.cc
+++ b/chrome/browser/chromeos/policy/device_local_account.cc
@@ -16,6 +16,7 @@
 #include "chrome/browser/chromeos/settings/cros_settings.h"
 #include "chromeos/login/user_names.h"
 #include "chromeos/settings/cros_settings_names.h"
+#include "components/user_manager/user_id.h"
 #include "google_apis/gaia/gaia_auth_util.h"
 
 namespace policy {
@@ -42,7 +43,7 @@ DeviceLocalAccount::DeviceLocalAccount(Type type,
 DeviceLocalAccount::~DeviceLocalAccount() {
 }
 
-std::string GenerateDeviceLocalAccountUserId(const std::string& account_id,
+user_manager::UserID GenerateDeviceLocalAccountUserId(const std::string& account_id,
                                              DeviceLocalAccount::Type type) {
   std::string domain_prefix;
   switch (type) {
@@ -56,18 +57,20 @@ std::string GenerateDeviceLocalAccountUserId(const std::string& account_id,
       NOTREACHED();
       break;
   }
-  return gaia::CanonicalizeEmail(
+
+  const std::string email = gaia::CanonicalizeEmail(
       base::HexEncode(account_id.c_str(), account_id.size()) + "@" +
       domain_prefix + kDeviceLocalAccountDomainSuffix);
+  return user_manager::UserID(std::string() /* gaia_id */, email);
 }
 
-bool IsDeviceLocalAccountUser(const std::string& user_id,
+bool IsDeviceLocalAccountUser(const user_manager::UserID& user_id,
                               DeviceLocalAccount::Type* type) {
   // For historical reasons, the guest user ID does not contain an @ symbol and
   // therefore, cannot be parsed by gaia::ExtractDomainName().
-  if (user_id == chromeos::login::kGuestUserName)
+  if (user_id == chromeos::login::GetGuestUserID())
     return false;
-  const std::string domain = gaia::ExtractDomainName(user_id);
+  const std::string domain = gaia::ExtractDomainName(user_id.GetUserEmail());
   if (!EndsWith(domain, kDeviceLocalAccountDomainSuffix, true))
     return false;