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

chrome/browser/resources/chromeos/switch_access/BUILD.gn

 # 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.
 
 import("//build/config/features.gni")
 import("//testing/test.gni")
 import("//chrome/test/base/js2gtest.gni")
 import("//chrome/browser/resources/chromeos/chromevox/run_jsbundler.gni")
 
 assert(is_chromeos)
 
 switch_access_dir = "$root_out_dir/resources/chromeos/switch_access"
 
 group("switch_access") {
   deps = [
     ":switch_access_copied_files",
     ":switch_access_guest_manifest",
     ":switch_access_manifest",
   ]
 }
 
 # Instead of setting up one copy target for each subdirectory, use a script
 # to copy all files.
 run_jsbundler("switch_access_copied_files") {
   mode = "copy"
   dest_dir = switch_access_dir
   sources = [
+    "auto_scan_manager.js",
     "background.js",
+    "keyboard_handler.js",
     "options.css",
     "options.html",
     "options.js",
     "prefs.js",
     "switch_access.js",
+    "tree_walker.js",
   ]
   rewrite_rules = [
     rebase_path(".", root_build_dir) + ":",
     rebase_path(closure_library_dir, root_build_dir) + ":closure",
   ]
 }
 
 # TODO: refactor this into another file like generate_manifest.gni
 # to share with other extensions.
 template("manifest") {
@@ skipping 27 matching lines @@
 }
 
 manifest("switch_access_manifest") {
   output_file = "$switch_access_dir/manifest.json"
 }
 
 manifest("switch_access_guest_manifest") {
   output_file = "$switch_access_dir/manifest_guest.json"
   is_guest_manifest = true
 }