Remove the compile time flag for DATALIST Element.

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 470 matching lines @@
     margin: auto 0;
 }
 
 input[type="search"]::-webkit-search-results-button {
     -webkit-appearance: searchfield-results-button;
     display: block;
     -webkit-flex: none;
     -webkit-user-modify: read-only !important;
 }
 
-#if defined(ENABLE_DATALIST_ELEMENT) && ENABLE_DATALIST_ELEMENT

[tkent, 2013/05/07 01:14:03]

It makes <datalist> display:none even if the runtime flags is off, and feature
detection in web sites will fail.  This rule should be added in
RenderTheme::extraDefaultStyleSheet depending on the runtime flag.

 datalist {
     display: none;
 }
-#endif
 
 #if defined(ENABLE_INPUT_MULTIPLE_FIELDS_UI) && ENABLE_INPUT_MULTIPLE_FIELDS_UI
 input[type="date"] {
     -webkit-align-items: center;
     display: -webkit-inline-flex;
     font-family: monospace;
     overflow: hidden;
     padding: 0;
     -webkit-padding-start: 1px;
 }
@@ skipping 375 matching lines @@
     height: 100%
 }
 
 input[type="color"]::-webkit-color-swatch {
     background-color: #000000;
     border: 1px solid #777777;
     -webkit-flex: 1;
     -webkit-user-modify: read-only !important;
 }
 
-#if defined(ENABLE_DATALIST_ELEMENT) && ENABLE_DATALIST_ELEMENT
-
 input[type="color"][list] {
     -webkit-appearance: menulist;
     width: 88px;
     height: 23px;
 }
 
 input[type="color"][list]::-webkit-color-swatch-wrapper {
     padding-left: 8px;
     padding-right: 24px;
 }
 
 input[type="color"][list]::-webkit-color-swatch {
     border-color: #000000;
 }
 
-#endif // defined(ENABLE_DATALIST_ELEMENT) && ENABLE_DATALIST_ELEMENT
 
 #endif // defined(ENABLE_INPUT_TYPE_COLOR) && ENABLE_INPUT_TYPE_COLOR
 
 #if defined(ENABLE_CALENDAR_PICKER) && ENABLE_CALENDAR_PICKER
 input::-webkit-calendar-picker-indicator {
     display: inline-block;
     width: 0.66em;
     height: 0.66em;
     padding: 0.17em 0.34em;
     -webkit-user-modify: read-only !important;
@@ skipping 372 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. */