[uber] change a padding from em to px

chrome/browser/resources/uber/uber_frame.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. */
 
 body {
   overflow: hidden;
   padding-top: 20px;
 }
 
 h1 {
   -webkit-margin-after: 1em;
-  -webkit-margin-before: 1.2em;
+  /* This value must match the top padding of the uber page header. */
+  -webkit-margin-before: 21px;
   -webkit-margin-start: 23px;
   color: rgb(92, 97, 102);
 }
 
 ul {
   list-style-type: none;
   padding: 0;
 }
 
 li {
@@ skipping 11 matching lines @@
 }
 
 li.selected {
   -webkit-border-start-color: rgb(78, 87, 100);
   color: rgb(70, 78, 90);
 }
 
 #helpNavItem {
   margin-top: 27px;
 }