Remove some pre-md code and assets.

ash/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.

[tdanderson, 2017/03/22 23:23:07]

nit: In the cl title or description it would be good to include mention of which
classes / features are being touched. This makes the CL easier to identify (or
rule out) when hunting down a regression.

[Evan Stade, 2017/03/23 15:55:36]

I think the file names pretty much do that. I'm not sure including the term
"PowerStatus" when the log shows you're modifying power_status.cc is an extra
benefit.

Granted, it isn't always obvious how to connect the filename/class name to
user-visible feature or UI. But if something breaks on chromeos only and it has
to do with power, settings, brightness, or the session length notifications then
it seems like the touched file list is a pretty good clue; also, if there's a
crash stack it lists file names.

 # 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
 # Windows 8 Metro mode. Windows support was removed in 2016.
@@ skipping 287 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 1187 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",
   ]
 }