Add bottom margin to overlay page h1 instead of top padding on content-area.

chrome/browser/resources/shared/css/overlay.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. */
 
 /* The shield that overlays the background. */
 .overlay {
   -webkit-box-align: center;
   -webkit-box-orient: vertical;
   -webkit-box-pack: center;
   -webkit-transition: 200ms opacity;
@@ skipping 64 matching lines @@
   background-image: url('chrome://resources/images/x-hover.png');
 }
 
 .overlay .page h1 {
   -webkit-padding-end: 24px;
   -webkit-user-select: none;
   color: #333;
   /* 120% of the body's font-size of 84% is 16px. This will keep the relative
    * size between the body and these titles consistent. */
   font-size: 120%;
-  margin: 0;
-  padding: 14px 17px 0;
+  margin: 14px 17px 14px;
   text-shadow: white 0 1px 2px;
 }
 
 .overlay .page .content-area {
   -webkit-box-flex: 1;
   overflow: auto;
-  padding: 14px 17px 6px;
+  padding: 6px 17px 6px;
 }
 
 .overlay .page .action-area {
   -webkit-box-align: center;
   -webkit-box-orient: horizontal;
   -webkit-box-pack: end;
   display: -webkit-box;
   padding: 14px;
 }
 
 html[dir='rtl'] .overlay .page .action-area {
   left: 0;
 }
 
 .overlay .page .action-area-right {
   display: -webkit-box;
 }
 
 .overlay .page .button-strip {
   -webkit-box-orient: horizontal;
   display: -webkit-box;
 }
 
 .overlay .page .button-strip > button {
   -webkit-margin-start: 10px;
   display: block;
 }