Set keys for SwitchAccessEventHandler to capture using accessibiltyPrivate API

chrome/browser/resources/chromeos/switch_access/keyboard_handler.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.
 
 // TODO(elichtenberg): Move into custom logger class or somewhere else.
 let debuggingEnabled = true;
 
 /**
  * Class to handle keyboard input.
  *
@@ skipping 10 matching lines @@
   this.init_();
 }
 
 KeyboardHandler.prototype = {
   /**
    * Set up key listener.
    *
    * @private
    */
   init_: function() {
+    // Capture keycodes for keys 1 through 4, and 6 through 9.
+    chrome.accessibilityPrivate.setSwitchAccessKeys(
+        ['1'.charCodeAt(0), '2'.charCodeAt(0), '3'.charCodeAt(0),

[Devlin, 2017/05/30 19:22:03]

optional: to me, this would potentially be more readable (and less prone to
error) as:
// Capture keycodes for keys 1 through 4, and 6 through 9.
var keys = ['1', '2', '3', '4', '6', '7', '8', '9'].map(function(key) { return
key.charCodeAt(0); });

But up to you.

[elichtenberg, 2017/05/31 00:58:43]

Good idea. I changed it to an arrow function too, so that should also make it
cleaner.

+        '4'.charCodeAt(0), '6'.charCodeAt(0), '7'.charCodeAt(0),
+        '8'.charCodeAt(0), '9'.charCodeAt(0)]);
     document.addEventListener('keyup', this.handleKeyEvent_.bind(this));
   },
 
   /**
    * Handle a keyboard event by calling the appropriate SwitchAccess functions.
    *
    * @param {!Event} event
    * @private
    */
   handleKeyEvent_: function(event) {
@@ skipping 30 matching lines @@
           break;
         case '9':
           console.log('9 = go to parent element (debug mode)');
           this.switchAccess_.debugMoveToParent();
           break;
       }
     }
     this.switchAccess_.performedUserAction();
   }
 };