Use PageManager in About page

chrome/browser/resources/help/help_content.css

Index: chrome/browser/resources/help/help_content.css
diff --git a/chrome/browser/resources/help/help.css b/chrome/browser/resources/help/help_content.css
similarity index 90%
copy from chrome/browser/resources/help/help.css
copy to chrome/browser/resources/help/help_content.css
index 6b40922763ac7fff841d10b9c71e96e922c2883b..06bdcfb6da2f2f35ce0c71abb0a1fa4028726eb1 100644
--- a/chrome/browser/resources/help/help.css
+++ b/chrome/browser/resources/help/help_content.css
@@ -1,19 +1,11 @@
-/* Copyright (c) 2012 The Chromium Authors. All rights reserved.
+/* Copyright 2014 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 {
-  -webkit-user-select: text;
-}
-
-#overlay .page:not(.showing) {
-  display: none;
-}
-
 #about-container {
-  -webkit-box-align: center;
-  display: -webkit-box;
+  align-items: center;
+  display: flex;
   margin-top: 10px;
 }
 
@@ -55,6 +47,10 @@ body {
   margin-top: 200px;
 }
 
+.overlay #product-container {
+  margin-top: 40px;
+}
+
 .help-page-icon,
 .help-page-icon-large {
   background-repeat: no-repeat;
@@ -127,7 +123,7 @@ body {
 }
 
 .channel-change-error-bubble {
-  display: -webkit-box;
+  display: flex;
 }
 
 .channel-change-error-icon {