[Merge to M53] Remove "Go Back/Forward" from keyboard overlay

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 537 matching lines @@
     var shortcutId = shortcutData[getAction(keyLabel, normModifiers)];
     if (modifiers.length == 0 &&
         (identifier == '2A' || identifier == '36')) {
       // Either the right or left shift keys are used to disable the caps lock
       // if it was enabled. To fix crbug.com/453623.
       shortcutId = 'keyboardOverlayDisableCapsLock';
     }
 
     classes.push('keyboard-overlay-key-background');
 
+    if ((shortcutId == 'keyboardOverlayGoBack' ||
+         shortcutId == 'keyboardOverlayGoForward') &&
+        !loadTimeData.getBoolean('backspaceGoesBackFeatureEnabled')) {
+      // If the "backspace key goes back" experiment is not enabled, then we
+      // clear the shortcuts for Backspace and Shift+Backspace to go back or
+      // forward respectively.
+      shortcutId = null;
+    }
+
     if (shortcutId) {
       classes.push('is-shortcut');
       classes.push('keyboard-overlay-shortcut-key-background');
     }
 
     var key = $(keyId(identifier, i));
     key.className = classes.join(' ');
 
     if (!keyData) {
       continue;
@@ skipping 361 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);