webui: minimize webui flicker.

ui/webui/resources/css/chrome_shared.css

 /* Copyright (c) 2012 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. */
 
 /* This file holds CSS that should be shared, in theory, by all user-visible
  * chrome:// pages. */
 
+@import url("text_defaults.css");
 @import url("widgets.css");
 <if expr="chromeos">
   @import url("chromeos/ui_account_tweaks.css");
 </if>
 
 /* Prevent CSS from overriding the hidden property. */
 [hidden] {
   display: none !important;
 }
 
@@ skipping 83 matching lines @@
 }
 
 /* WebKit does not honor alignment for text specified via placeholder attribute.
  * This CSS is a workaround. Please remove once WebKit bug is fixed.
  * https://bugs.webkit.org/show_bug.cgi?id=63367
  */
 html[dir='rtl'] input.weakrtl::-webkit-input-placeholder,
 html[dir='rtl'] .weakrtl input::-webkit-input-placeholder {
   direction: rtl;
 }