Added to options page to let users change keyboard mappings.

chrome/browser/resources/chromeos/switch_access/tree_walker.js

 // Copyright 2017 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.
 
 /**
  * Class to move to the appropriate node in the accessibility tree. Stays in a
  * subtree determined by restrictions passed to it.
  *
  * @constructor
  * @param {!chrome.automation.AutomationNode} start
@@ skipping 127 matching lines @@
     if (node === this.scope_)
       return undefined;
 
     // Check for left-sibling. If a left-sibling exists, return its youngest
     // descendant if it has one, or otherwise return the sibling.
     let sibling = node.previousSibling;
     if (sibling)
       return this.getYoungestDescendant_(sibling) || sibling;
 
     // No left-sibling. Return parent if it exists; otherwise return undefined.
-    // return node.parent;
     let parent = node.parent;
     if (parent)
       return parent;
 
     return undefined;
   },
 
   /**
    * Get the youngest descendant of |node|, if it has one, within the current
    * scope.
@@ skipping 85 matching lines @@
     let parent = node.parent;
     if (parent) {
       return parent;
     } else {
       console.log('Node has no parent');
       console.log('\n');
       return null;
     }
   }
 };