Refactor: Extract a KeyboardHandler and CommandHandler from Background

chrome/browser/resources/chromeos/chromevox/chromevox.gni

 # Copyright 2015 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.
 # Common variables shared amongst all ChromeVox targets.
 
 assert(is_chromeos)
 
 # TODO(plundblad): Move the below variables to BUILD.gn when crbug.com/395883
 # is resolved.
 
@@ skipping 110 matching lines @@
   "common/traverse_math.js",
   "common/traverse_table.js",
   "common/traverse_util.js",
   "common/xpath_util.js",
   "cvox2/background/automation_object_constructor_installer.js",
   "cvox2/background/automation_predicate.js",
   "cvox2/background/automation_util.js",
   "cvox2/background/background.js",
   "cvox2/background/base_automation_handler.js",
   "cvox2/background/chromevox_state.js",
+  "cvox2/background/command_handler.js",
   "cvox2/background/constants.js",
   "cvox2/background/cursors.js",
   "cvox2/background/desktop_automation_handler.js",
   "cvox2/background/earcon_engine.js",
   "cvox2/background/editing.js",
   "cvox2/background/i_search.js",
+  "cvox2/background/keyboard_handler.js",
   "cvox2/background/live_regions.js",
   "cvox2/background/next_earcons.js",
   "cvox2/background/notifications.js",
   "cvox2/background/output.js",
   "cvox2/background/panel.js",
   "cvox2/background/panel_command.js",
   "cvox2/background/panel_menu.js",
   "cvox2/background/panel_menu_item.js",
   "cvox2/background/stubs.js",
   "cvox2/background/tabs_automation_handler.js",
@@ skipping 66 matching lines @@
   "string/string.js",
   "dom/nodetype.js",
   "base.js",
   "asserts/asserts.js",
   "debug/error.js",
   "object/object.js",
 ]
 
 closure_library_modules =
     rebase_path(relative_closure_library_modules, ".", closure_library_dir)