Fix keyboard overlay when the Search key is mapped to Backspace

chrome/browser/resources/chromeos/keyboard_overlay.js

 // 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.
 
 <include src="keyboard_overlay_data.js">
 
 var BASE_KEYBOARD = {
   top: 0,
   left: 0,
   width: 1237,
@@ skipping 23 matching lines @@
   'E0 38': 'is-alt',
   'E0 5B': 'is-search'
 };
 
 var LABEL_TO_IDENTIFIER = {
   'search': 'E0 5B',
   'ctrl': '1D',
   'alt': '38',
   'caps lock': '3A',
   'esc': '01',
+  'backspace': '0E',
   'disabled': 'DISABLED'
 };
 
 var KEYCODE_TO_LABEL = {
   8: 'backspace',
   9: 'tab',
   13: 'enter',
   27: 'esc',
   32: 'space',
   33: 'pageup',
@@ skipping 813 matching lines @@
 function onWidgetShown() {
   setTimeout(function() {
     // Show and focus the instructions div after a delay so that chrome vox
     // speaks it correctly.
     $('instructions').style.visibility = 'visible';
     $('instructions').focus();
   }, 500);
 }
 
 document.addEventListener('DOMContentLoaded', init);