Reland: mash: Fix MusPropertyMirrorAsh for owned properties; add test.

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 127 matching lines @@
     "wm_window_test_api.h",
   ]
   configs += [ "//build/config:precompiled_headers" ]
 
   public_deps = [
     "//ash",
     "//ui/display:display_manager_test_api",
   ]
   deps = [
     "//ash/common/test:test_support",
-    "//ash/public/cpp",
+    "//ash/public/cpp:ash_public_cpp",
     "//ash/public/interfaces",
     "//ash/resources",
     "//base:i18n",
     "//base/test:test_support",
     "//chromeos",
     "//components/signin/core/account_id",
     "//components/user_manager:user_manager",
     "//device/bluetooth",
     "//services/ui/public/interfaces",
     "//skia",
@@ skipping 39 matching lines @@
   deps = [
     ":test_support_with_content",
     "//base",
     "//skia",
     "//testing/gtest",
     "//ui/aura",
     "//ui/base",
     "//ui/gl:test_support",
   ]
 }