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

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

Index: chrome/browser/resources/chromeos/switch_access/switch_access_interface.js
diff --git a/chrome/browser/resources/chromeos/switch_access/switch_access_interface.js b/chrome/browser/resources/chromeos/switch_access/switch_access_interface.js
new file mode 100644
index 0000000000000000000000000000000000000000..7bbc6fe72e9c10fd4ea43d7634a7ac4882cf15e6
--- /dev/null
+++ b/chrome/browser/resources/chromeos/switch_access/switch_access_interface.js
@@ -0,0 +1,35 @@
+// 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
+ */
+let SwitchAccessInterface = function() {
+  /**
+   * @type {SwitchAccessPrefs}
+   */
+  this.switchAccessPrefs = null;
+};
+
+SwitchAccessInterface.prototype = {
+  moveToNext: function() {},
+
+  moveToPrevious: function() {},
+
+  doDefault: function() {},
+
+  showOptionsPage: function() {},
+
+  performedUserAction: function() {},
+
+  debugMoveToNext: function() {},
+
+  debugMoveToPrevious: function() {},
+
+  debugMoveToFirstChild: function() {},
+
+  debugMoveToParent: function() {}
+};