Remove some pre-md code and assets.

ash/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("//testing/test.gni")
 import("//ui/base/ui_features.gni")
 
 # Historical note: Ash shipped on Windows for a couple years to support
@@ skipping 292 matching lines @@
     "common/system/chromeos/session/logout_button_observer.h",
     "common/system/chromeos/session/logout_button_tray.cc",
     "common/system/chromeos/session/logout_button_tray.h",
     "common/system/chromeos/session/logout_confirmation_controller.cc",
     "common/system/chromeos/session/logout_confirmation_controller.h",
     "common/system/chromeos/session/logout_confirmation_dialog.cc",
     "common/system/chromeos/session/logout_confirmation_dialog.h",
     "common/system/chromeos/session/session_length_limit_observer.h",
     "common/system/chromeos/session/tray_session_length_limit.cc",
     "common/system/chromeos/session/tray_session_length_limit.h",
-    "common/system/chromeos/settings/tray_settings.cc",
-    "common/system/chromeos/settings/tray_settings.h",
     "common/system/chromeos/supervised/custodian_info_tray_observer.h",
     "common/system/chromeos/supervised/tray_supervised_user.cc",
     "common/system/chromeos/supervised/tray_supervised_user.h",
     "common/system/chromeos/system_clock_observer.cc",
     "common/system/chromeos/system_clock_observer.h",
     "common/system/chromeos/tray_caps_lock.cc",
     "common/system/chromeos/tray_caps_lock.h",
     "common/system/chromeos/tray_tracing.cc",
     "common/system/chromeos/tray_tracing.h",
     "common/system/chromeos/virtual_keyboard/virtual_keyboard_observer.h",
@@ skipping 1182 matching lines @@
     "//content/public/app:both",
     "//device/bluetooth",
   ]
 
   data_deps = [
     "//ash/strings:ash_test_strings",
     "//ash/resources:ash_test_resources_with_content_100_percent",
     "//ash/resources:ash_test_resources_200_percent",
   ]
 }