Remove display-options-display-view-mirroring.

chrome/browser/resources/options/chromeos/display_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. */
 
 #display-options-page {
   background-color: rgb(240, 240, 240);
 }
 
 #display-options-content-area {
   padding: 0;
 }
 
 #display-options-displays-view-host {
   padding: 20px 0 20px 0;
 }
 
 #display-options-displays-view {
   overflow: hidden;
   position: relative;
   width: 100%;
 }
 
-#display-options-displays-view-mirroring {
-  margin: 20px 0 20px 0;
-}
-
 #display-configurations {
   -webkit-padding-end: 0;
   -webkit-padding-start: 15px;
   background-color: white;
   border-top: 1px solid lightgrey;
   padding-bottom: 15px;
   padding-top: 15px;
 }
 
 /* The arrow at the border #display-configurations to point the focused display.
@@ skipping 50 matching lines @@
   color: rgb(0, 138, 255);
 }
 
 #display-options-toggle-mirroring {
   margin-right: 5px;
 }
 
 .display-options-button {
   width: 130px;
 }