I see a warning like this when booting a ToT samus image:

[2133:2133:0809/143856:WARNING:child_account_service.cc(302)] User instance wasn't found while setting child account flag.

I'm not using supervised users.

Here's the code:

void ChildAccountService::PropagateChildStatusToUser(bool is_child) {
#if defined(OS_CHROMEOS)
  user_manager::User* user =
      chromeos::ProfileHelper::Get()->GetUserByProfile(profile_);
  if (user) {
    user_manager::UserManager::Get()->ChangeUserChildStatus(user, is_child);
  } else {
    LOG(WARNING) <<
        "User instance wasn't found while setting child account flag.";
  }
#endif
}

I think we should check that this isn't the signin profile before logging the warning.