Added to options page to let users change keyboard mappings.

chrome/browser/resources/chromeos/switch_access/switch_access_interface.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.
 
 /**
  * Interface for controllers to interact with main SwitchAccess class.
  *
  * @interface
  */
-function SwitchAccessInterface() {
-  /**
-   * @type {SwitchAccessPrefs}
-   */
-  this.switchAccessPrefs = null;
-}
+function SwitchAccessInterface() {}
 
 SwitchAccessInterface.prototype = {
+  /**
+   * Move to the next/previous interesting node. If |doNext| is true, move to
+   * the next node. Otherwise, move to the previous node.
+   *
+   * @param {boolean} doNext
+   */
   moveToNode: function(doNext) {},
 
+  /**
+   * Perform the default action on the current node.
+   */
   selectCurrentNode: function() {},
 
+  /**
+   * Open the options page in a new tab.
+   */
   showOptionsPage: function() {},
 
+  /**
+   * Return a list of the names of all user commands.
+   *
+   * @return {!Array<string>}
+   */
+  getCommands: function() {},
+
+  /**
+   * Return the default key code for a command.
+   *
+   * @param {string} command
+   * @return {number}
+   */
+  getDefaultKeyCodeFor: function(command) {},
+
+  /**
+   * Run the function binding for the specified command.
+   *
+   * @param {string} command
+   */
+  runCommand: function(command) {},
+
+  /**
+   * Perform actions as the result of actions by the user. Currently, restarts
+   * auto-scan if it is enabled.
+   */
   performedUserAction: function() {},
 
+  /**
+   * Set the value of the preference |key| to |value| in chrome.storage.sync.
+   * this.prefs_ is not set until handleStorageChange_.
+   *
+   * @param {string} key
+   * @param {boolean|string|number} value
+   */
+  setPref: function(key, value) {},
+
+  /**
+   * Get the value of type 'boolean' of the preference |key|. Will throw a type
+   * error if the value of |key| is not 'boolean'.
+   *
+   * @param  {string} key
+   * @return {boolean}
+   */
+  getBooleanPref: function(key) {},
+
+  /**
+   * Get the value of type 'number' of the preference |key|. Will throw a type
+   * error if the value of |key| is not 'number'.
+   *
+   * @param  {string} key
+   * @return {number}
+   */
+  getNumberPref: function(key) {},
+
+  /**
+   * Get the value of type 'string' of the preference |key|. Will throw a type
+   * error if the value of |key| is not 'string'.
+   *
+   * @param  {string} key
+   * @return {string}
+   */
+  getStringPref: function(key) {},
+
+  /**
+   * Returns true if |keyCode| is already used to run a command from the
+   * keyboard.
+   *
+   * @param {number} keyCode
+   * @return {boolean}
+   */
+  keyCodeIsUsed: function(keyCode) {},
+
+  /**
+   * Move to the next sibling of the current node if it has one.
+   */
   debugMoveToNext: function() {},
 
+  /**
+   * Move to the previous sibling of the current node if it has one.
+   */
   debugMoveToPrevious: function() {},
 
+  /**
+   * Move to the first child of the current node if it has one.
+   */
   debugMoveToFirstChild: function() {},
 
+  /**
+   * Move to the parent of the current node if it has one.
+   */
   debugMoveToParent: function() {}
 };