Add policy provider that would filter extensions/apps allowed on the

chrome/browser/chromeos/BUILD.gn

 # Copyright 2014 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("//build/config/ui.gni")
 import("//media/media_options.gni")
 import("//third_party/protobuf/proto_library.gni")
 
 assert(is_chromeos)
@@ skipping 374 matching lines @@
     "extensions/input_method_event_router.cc",
     "extensions/input_method_event_router.h",
     "extensions/install_limiter.cc",
     "extensions/install_limiter.h",
     "extensions/install_limiter_factory.cc",
     "extensions/install_limiter_factory.h",
     "extensions/launcher_search_provider.cc",
     "extensions/launcher_search_provider.h",
     "extensions/media_player_event_router.cc",
     "extensions/media_player_event_router.h",
+    "extensions/signin_screen_policy_provider.cc",
+    "extensions/signin_screen_policy_provider.h",
     "external_metrics.cc",
     "external_metrics.h",
     "external_protocol_dialog.cc",
     "external_protocol_dialog.h",
     "feedback_util.cc",
     "feedback_util.h",
     "file_manager/app_id.h",
     "file_manager/arc_file_tasks.cc",
     "file_manager/arc_file_tasks.h",
     "file_manager/file_browser_handlers.cc",
@@ skipping 1211 matching lines @@
     "policy/proto/chrome_device_policy.proto",
     "policy/proto/install_attributes.proto",
   ]
 }
 
 proto_library("attestation_proto") {
   sources = [
     "attestation/attestation_key_payload.proto",
   ]
 }