Fix regression caused by r178354 where options in optgroup not indented

Source/core/css/html.css

 /*
  * The default style sheet used to render HTML.
  *
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 773 matching lines @@
 }
 
 option {
     font-weight: normal;
     display: block;
     padding: 0 2px 1px 2px;
     white-space: pre;
     min-height: 1.2em;
 }
 
+select:-internal-list-box optgroup option:before {
+    content: "\00a0\00a0\00a0\00a0";;
+}
+
 select:-internal-list-box option,
 select:-internal-list-box optgroup {
     line-height: initial !important;
 }
 
 select:-internal-list-box:focus option:checked {
     background-color: -internal-active-list-box-selection !important;
     color: -internal-active-list-box-selection-text !important;
 }
 
@@ skipping 294 matching lines @@
 @page {
     /* FIXME: Define the right default values for page properties. */
     size: auto;
     margin: auto;
     padding: 0px;
     border-width: 0px;
 }
 
 /* noscript is handled internally, as it depends on settings. */