Regression: Add back support for hr elements in select listbox

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 793 matching lines @@
 select:-internal-list-box option:checked {
     background-color: -internal-inactive-list-box-selection !important;
     color: -internal-inactive-list-box-selection-text !important;
 }
 
 select:-internal-list-box:disabled option:checked,
 select:-internal-list-box option:checked:disabled {
     color: gray !important;
 }
 
+select:-internal-list-box hr {
+    border-style: none;
+}
 
 output {
     display: inline;
 }
 
 /* meter */
 
 meter {
     -webkit-appearance: meter;
     box-sizing: border-box;
@@ skipping 274 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. */