Use PageManager in About page

chrome/browser/resources/options/options_page.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 {
   position: relative;
 }
 
 #main-content {
   bottom: 0;
@@ skipping 19 matching lines @@
   min-height: 100%;
   position: relative;
 }
 
 #page-container {
   box-sizing: border-box;
   max-width: 888px;
   min-width: 600px;
 }
 
-body.uber-frame #searchBox {
+body #searchBox {
   position: fixed;
   z-index: 4;
 }
 
 div.disabled {
   color: #999;
 }
 
 .settings-row {
   display: block;
@@ skipping 11 matching lines @@
 }
 
 .box-align-center {
   -webkit-box-align: center;
 }
 
 .stretch {
   -webkit-box-flex: 1;
 }
 
-.frozen {
-  position: fixed;
-}
-
-#overlay-container-1 {
-  z-index: 11;
-}
-#overlay-container-2 {
-  z-index: 12;
-}
-#overlay-container-3 {
-  z-index: 13;
-}
-
 .raw-button,
 .raw-button:hover,
 .raw-button:active {
   -webkit-box-shadow: none;
   background-color: transparent;
   background-repeat: no-repeat;
   border: none;
   min-width: 0;
   padding: 1px 6px;
 }
@@ skipping 15 matching lines @@
 
 .page list {
   /* Min height is a multiple of the list item height (32) */
   min-height: 192px;
 }
 
 .option {
   margin-top: 0;
 }
 
-.transparent {
-  opacity: 0;
-}
-
 .touch-slider {
   -webkit-appearance: slider-horizontal;
 }
 
 .settings-list,
 .settings-list-empty {
   border: 1px solid #d9d9d9;
   border-radius: 2px;
 }
 
@@ skipping 315 matching lines @@
 html:not([hasFlashPlugin]) .flash-plugin-area,
 /* If the Flash plug-in supports the NPP_ClearSiteData API, we don't need to
  * show the link to the Flash storage settings manager:
  */
 html[flashPluginSupportsClearSiteData] .flash-plugin-area,
 html:not([flashPluginSupportsClearSiteData]) .clear-plugin-lso-data-enabled,
 html[flashPluginSupportsClearSiteData] .clear-plugin-lso-data-disabled,
 html:not([enablePepperFlashSettings]) .pepper-flash-settings {
   display: none;
 }