separate about page into its own page (included in chrome://chrome)

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;
+}
+
+span {
   line-height: 22px;
-  margin: 0;
 }
 
 h1 {
   color: rgb(17, 85, 204);
   font-size: 18px;
   font-weight: normal;
 }
 
 a:link {
   color: rgb(63, 110, 194);
@@ skipping 49 matching lines @@
 }
 
 /* WebKit does not honor alignment for text specified via placeholder attrib.
  * 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;
 }