Implement select listbox using shadow DOM

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 623 matching lines @@
 }
 
 input[type="button"]:active, input[type="submit"]:active, input[type="reset"]:active, input[type="file"]:active::-webkit-file-upload-button, button:active {
     border-style: inset
 }
 
 input[type="button"]:active:disabled, input[type="submit"]:active:disabled, input[type="reset"]:active:disabled, input[type="file"]:active:disabled::-webkit-file-upload-button, button:active:disabled {
     border-style: outset
 }
 
+option:-internal-spatial-navigation-focus {
+    outline: black dashed 1px;
+    outline-offset: -1px;
+}
+
 datalist {
     display: none
 }
 
 area, param {
     display: none
 }
 
 input[type="checkbox"] {
     -webkit-appearance: checkbox;
@@ skipping 98 matching lines @@
     cursor: default;
 }
 
 select[size],
 select[multiple],
 select[size][multiple] {
     -webkit-appearance: listbox;
     align-items: flex-start;
     border: 1px inset gray;
     border-radius: initial;
-    white-space: initial;
+    overflow-x: hidden;
+    overflow-y: scroll;
+    vertical-align: text-bottom;
+    -webkit-user-select: none;
+    white-space: nowrap;
 }
 
 select[size="0"],
 select[size="1"] {
     -webkit-appearance: menulist;
     align-items: center;
-    border: 1px solid;
+    border-width: 1px;
+    border-style: solid;
+    border-color: initial;
     border-radius: 5px;
+    overflow-x: initial;
+    overflow-y: initial;
+    vertical-align: initial;
+    -webkit-user-select: initial;
     white-space: pre;
 }
 
 optgroup {
     font-weight: bolder;
+    display: block;
 }
 
 option {
     font-weight: normal;
+    display: block;
+    padding: 0 2px 1px 2px;
+    white-space: pre;
+    min-height: 1.2em;
+}
+
+option:checked {
+    background-color: -internal-inactive-list-box-selection;
+    color: -internal-inactive-list-box-selection-text;
+}
+
+select:focus option:checked {
+    background-color: -internal-active-list-box-selection;
+    color: -internal-active-list-box-selection-text;
+}
+
+select:disabled option:checked,
+option:checked:disabled {
+    color: gray;
 }
 
 output {
     display: inline;
 }
 
 /* meter */
 
 meter {
     -webkit-appearance: meter;
@@ skipping 249 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. */