Allow legacy supervised users to login with invalid oath tokens.

Currently we force online login for legacy supervised users when the oauth
token becomes invalid. However there is no online login for legacy supervised
users - we just print a cryptic error message, and there is no way to refresh
this oauth token, so the account is effectively locked.

BUG=chromium:659788
TEST=manual

Review-Url: https://codereview.chromium.org/2563573002
Cr-Commit-Position: refs/heads/master@{#438786}

chrome/browser/chromeos/login/screens/user_selection_screen.cc

@@ -232,13 +232,10 @@ void UserSelectionScreen::FillMultiProfileUserPrefs(
 bool UserSelectionScreen::ShouldForceOnlineSignIn(
     const user_manager::User* user) {
   // Public sessions are always allowed to log in offline.
-  // Supervised user are allowed to log in offline if their OAuth token status
-  // is unknown or valid.
+  // Supervised users are always allowed to log in offline.
   // For all other users, force online sign in if:
   // * The flag to force online sign-in is set for the user.
-  // * The user's OAuth token is invalid.
-  // * The user's OAuth token status is unknown (except supervised users,
-  //   see above).
+  // * The user's OAuth token is invalid or unknown.
   if (user->is_logged_in())
     return false;
 
@@ -249,10 +246,8 @@ bool UserSelectionScreen::ShouldForceOnlineSignIn(
   const bool is_public_session =
       user->GetType() == user_manager::USER_TYPE_PUBLIC_ACCOUNT;
 
-  if (is_supervised_user &&
-      token_status == user_manager::User::OAUTH_TOKEN_STATUS_UNKNOWN) {
+  if (is_supervised_user)
     return false;
-  }
 
   if (is_public_session)
     return false;