Added auto-scan, made some small changes to how prefs are stored, refactored.

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.
+ *
+ * @constructor
+ * @param {SwitchAccessInterface} switchAccess
+ */
+function KeyboardHandler(switchAccess) {
+  /**
+   * SwitchAccess reference.
+   * @private {SwitchAccessInterface}
+   */
+  this.switchAccess_ = switchAccess;
+
+  this.init_();
+};
+
+KeyboardHandler.prototype = {
+  /**
+   * Set up key listener.
+   *
+   * @private
+   */
+  init_: function() {
+    document.addEventListener('keyup', this.handleKeyEvent_.bind(this));
+  },
+
+  /**
+   * Handle a keyboard event by calling the appropriate SwitchAccess functions.
+   *
+   * @param {!Event} event
+   * @private
+   */
+  handleKeyEvent_: function(event) {
+    switch (event.key) {
+      case '1':
+        console.log('1 = go to next element');
+        this.switchAccess_.moveToNode(true);
+        break;
+      case '2':
+        console.log('2 = go to previous element');
+        this.switchAccess_.moveToNode(false);
+        break;
+      case '3':
+        console.log('3 = do default on element');
+        this.switchAccess_.doDefault();
+        break;
+      case '4':
+        this.switchAccess_.showOptionsPage();
+        break;
+    }
+    if (debuggingEnabled) {
+      switch (event.key) {
+        case '6':
+          console.log('6 = go to next element (debug mode)');
+          this.switchAccess_.debugMoveToNext();
+          break;
+        case '7':
+          console.log('7 = go to previous element (debug mode)');
+          this.switchAccess_.debugMoveToPrevious();
+          break;
+        case '8':
+          console.log('8 = go to child element (debug mode)');
+          this.switchAccess_.debugMoveToFirstChild();
+          break;
+        case '9':
+          console.log('9 = go to parent element (debug mode)');
+          this.switchAccess_.debugMoveToParent();
+          break;
+      }
+    }
+    this.switchAccess_.performedUserAction();
+  }
+};