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

chrome/browser/chromeos/profiles/profile_helper.cc

Index: chrome/browser/chromeos/profiles/profile_helper.cc
diff --git a/chrome/browser/chromeos/profiles/profile_helper.cc b/chrome/browser/chromeos/profiles/profile_helper.cc
index cb7f6e2f444fa587de2df77f9f6284778b49a179..1effa5188575a27c19a17feff9d0d7fba9402ac5 100644
--- a/chrome/browser/chromeos/profiles/profile_helper.cc
+++ b/chrome/browser/chromeos/profiles/profile_helper.cc
@@ -166,7 +166,7 @@ bool ProfileHelper::IsOwnerProfile(Profile* profile) {
   if (!user)
     return false;
 
-  return user->email() == user_manager::UserManager::Get()->GetOwnerEmail();
+  return user->GetUserID() == user_manager::UserManager::Get()->GetOwnerID();
 }
 
 // static
@@ -281,7 +281,7 @@ Profile* ProfileHelper::GetProfileByUserUnsafe(const user_manager::User* user) {
                     "|user|'s profile is not created. It probably means that "
                     "something is wrong with a calling code. Please report in "
                     "http://crbug.com/361528 if you see this message. user_id: "
-                 << user->email();
+                 << user->GetUserID().GetUserEmail();
     profile = ProfileManager::GetActiveUserProfile();
   }
 
@@ -299,12 +299,12 @@ const user_manager::User* ProfileHelper::GetUserByProfile(
     if (always_return_primary_user_for_testing)
       return user_manager::UserManager::Get()->GetPrimaryUser();
 
-    const std::string& user_name = profile->GetProfileUserName();
+    const user_manager::UserID user_id = user_manager::UserID::FromUserEmail(profile->GetProfileUserName());
     for (user_manager::UserList::const_iterator it =
              user_list_for_testing_.begin();
          it != user_list_for_testing_.end();
          ++it) {
-      if ((*it)->email() == user_name)
+      if ((*it)->GetUserID() == user_id)
         return *it;
     }