Extract LazyBackgroundTaskQueue from ExtensionSystem.

extensions/extensions.gypi

 # 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.
 
 {
   'variables': {
     'extensions_common_constants_sources': [
       'common/constants.cc',
       'common/constants.h',
     ],
@@ skipping 675 matching lines @@
       'browser/info_map.cc',
       'browser/info_map.h',
       'browser/install/crx_installer_error.h',
       'browser/install/extension_install_ui.cc',
       'browser/install/extension_install_ui.h',
       'browser/install_flag.h',
       'browser/io_thread_extension_message_filter.cc',
       'browser/io_thread_extension_message_filter.h',
       'browser/lazy_background_task_queue.cc',
       'browser/lazy_background_task_queue.h',
+      'browser/lazy_background_task_queue_factory.cc',
+      'browser/lazy_background_task_queue_factory.h',
       'browser/load_monitoring_extension_host_queue.cc',
       'browser/load_monitoring_extension_host_queue.h',
       'browser/management_policy.cc',
       'browser/management_policy.h',
       'browser/mojo/keep_alive_impl.cc',
       'browser/mojo/keep_alive_impl.h',
       'browser/mojo/service_registration.cc',
       'browser/mojo/service_registration.h',
       'browser/mojo/stash_backend.cc',
       'browser/mojo/stash_backend.h',
@@ skipping 338 matching lines @@
       'test/result_catcher.h',
       'test/test_content_utility_client.cc',
       'test/test_content_utility_client.h',
       'test/test_extensions_client.cc',
       'test/test_extensions_client.h',
       'test/test_permission_message_provider.cc',
       'test/test_permission_message_provider.h',
     ],
   },
 }