[uber] make the navigation controls an iframe

chrome/browser/resources/shared/css/chrome_shared2.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. This contrasts chrome_shared.css, which it is meant to
  * replace, but has CSS specific to options and options-like pages. */
 
 /* Prevent CSS from overriding the hidden property. */
 [hidden] {
   display: none !important;
 }
 
 body {
   cursor: default;
   font-family: Open Sans, sans-serif;
   font-size: 12px;
   margin: 0;
 }
 
+body.uber-frame {
+  -webkit-margin-start: 155px;
+}
+
 p {
   line-height: 22px;
 }
 
 h1 {
   -webkit-user-select: none;
   color: rgb(48, 57, 66);
   font-size: 18px;
   font-weight: normal;
   margin-top: 1em;
@@ skipping 86 matching lines @@
  * For now it's a bandaid until we install open sans properly. */
 <if expr="not pp_ifdef('chromeos')">
 @font-face {
   font-family: 'Open Sans';
   font-style: normal;
   font-weight: 400;
   src: local('Open Sans'), local('OpenSans'),
       url('chrome://resources/fonts/open_sans.woff') format('woff');
 }
 </if>