Add back button to chrome://devices

chrome/browser/resources/local_discovery/local_discovery.css

 /* Copyright 2013 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 {
   margin: 21px 10px 24px 10px;
 }
 
 h1 {
   margin: 0 0 13px 0;
@@ skipping 90 matching lines @@
 .cloud-print-message {
   margin: 23px 0;
 }
 
 section {
   margin-bottom: 23px;
 }
 
 .dialog-contents {
     padding-left: 17px;
-}
+}
+
+#back-button {
+  background: url('chrome://theme/IDR_CHEVRON_LEFT') left no-repeat;
+  margin-bottom: 25px;
+  margin-top: 6px;
+  padding-left: 23px;
+}
+
+html[dir='rtl'] #back-button {
+  transform: scaleX(-1);
+}
+
+html[dir='rtl'] #back-button span {
+  display: inline-block;
+  transform: scaleX(-1);
+}