chromeos: convert remaining AshTest usage to AshTestBase

ash/mus/BUILD.gn

 # 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.
 
 import("//build/config/ui.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//services/service_manager/public/cpp/service.gni")
 import("//services/service_manager/public/service_manifest.gni")
 import("//tools/grit/repack.gni")
 
@@ skipping 173 matching lines @@
 }
 
 source_set("unittests") {
   testonly = true
 
   sources = [
     "app_launch_unittest.cc",
     "bridge/shell_port_mash_test_api.h",
     "non_client_frame_controller_unittest.cc",
     "screen_mus_unittest.cc",
-    "test/ash_test_impl_mus.cc",
-    "test/ash_test_impl_mus.h",
-    "test/wm_test_base.cc",
-    "test/wm_test_base.h",
-    "test/wm_test_helper.cc",
-    "test/wm_test_helper.h",
     "top_level_window_factory_unittest.cc",
     "window_manager_unittest.cc",
   ]
 
   deps = [
     ":lib",
     ":resources",
     "//ash",
     "//ash/public/cpp:ash_public_cpp",
     "//ash/test:test_support_without_content",
@@ skipping 25 matching lines @@
     "//ui/views/mus",
   ]
 
   data_deps = [
     ":mus",
     "//mash/quick_launch",
   ]
 
   defines = [ "NOTIMPLEMENTED_POLICY=5" ]
 }