Gut ash::MaterialDesignController, and remove the about:flags entry.

ash/test/BUILD.gn

 # Copyright 2016 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/ui.gni")
 
 # Used to test ash with an aura backend.
 source_set("ash_with_aura_test_support") {
   testonly = true
   sources = [
@@ skipping 57 matching lines @@
   testonly = true
   visibility = [ ":*" ]
   sources = [
     # TODO(jamescook): Move these files into ash/test.
     "../laser/laser_pointer_controller_test_api.cc",
     "../laser/laser_pointer_controller_test_api.h",
     "../laser/laser_pointer_points_test_api.cc",
     "../laser/laser_pointer_points_test_api.h",
     "../shell/toplevel_window.cc",
     "../shell/toplevel_window.h",
-    "ash_md_test_base.cc",
-    "ash_md_test_base.h",
     "ash_test_base.cc",
     "ash_test_base.h",
     "ash_test_environment.h",
     "ash_test_helper.cc",
     "ash_test_helper.h",
     "ash_test_views_delegate.cc",
     "ash_test_views_delegate.h",
     "child_modal_window.cc",
     "child_modal_window.h",
     "cursor_manager_test_api.cc",
@@ skipping 108 matching lines @@
   deps = [
     ":test_support_with_content",
     "//base",
     "//skia",
     "//testing/gtest",
     "//ui/aura",
     "//ui/base",
     "//ui/gl:test_support",
   ]
 }