Add button to reset auto-open pref in Chrome OS settings

chrome/browser/resources/options/browser_options.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. */
 
 #change-home-page-section {
   margin-left: 30px;
 }
 
 #home-page-url {
   display: inline-block;
@@ skipping 396 matching lines @@
 #privacy-explanation {
   line-height: 1.8em;
 }
 
 #advanced-settings {
   height: 0;
   margin-top: 8px;
   overflow: hidden;
 }
 
-#auto-open-file-types-label {
-  padding: 0.45em 0
-}
-
 .sliding {
   -webkit-transition: height 200ms;
   overflow-y: hidden;
 }
 
 #keyboard-overlay .option-value > select {
   width: 100%;
 }
 
 #keyboard-overlay table {
   /* Same as .settings-row {margin}. */
   -webkit-border-vertical-spacing: 0.65em;
 }
 
 #accessibility-autoclick .controlled-setting-with-label {
   -webkit-box-align: baseline;
 }
 
 #accessibility-autoclick label + select {
   /* Same as .controlled-setting-with-label > input + span. */
   -webkit-margin-start: 0.6em;
 }