Fixed suggesting adding more users into multi-profile session when we don't have more

ash/session/session_state_delegate.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/session/session_state_delegate.h"
 
 namespace ash {
 
 bool SessionStateDelegate::IsInSecondaryLoginScreen() const {
   return GetSessionState() ==
       ash::SessionStateDelegate::SESSION_STATE_LOGIN_SECONDARY;
 }
 
+bool SessionStateDelegate::CanAddUserToMultiProfile(
+    SessionStateDelegate::MultiProfileAddUserError* error) const {
+  if (!IsMultiProfileAllowedByPrimaryUserPolicy()) {
+    if (error)
+      *error = MULTIPROFILE_ADD_USER_ERROR_NOT_ALLOWED_PRIMARY_USER;
+    return false;
+  }
+  if (NumberOfLoggedInUsers() >= GetMaximumNumberOfLoggedInUsers()) {
+    if (error)
+      *error = MULTIPROFILE_ADD_USER_ERROR_MAXIMUM_OF_USERS_REACHED;
+    return false;
+  }
+  return true;
+}
+
 } // namespace ash