mash: Fix mash app shelf items; encapsulate ash property setup.

mash/task_viewer/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("//services/service_manager/public/cpp/service.gni")
 import("//services/service_manager/public/service_manifest.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 
 source_set("lib") {
   sources = [
     "task_viewer.cc",
     "task_viewer.h",
   ]
 
   deps = [
+    "//ash/public/cpp:ash_public_cpp",
     "//base",
     "//mash/public/interfaces",
     "//mojo/public/cpp/bindings",
     "//services/catalog/public/interfaces",
     "//services/service_manager/public/cpp",
     "//services/service_manager/public/interfaces",
     "//ui/resources",
     "//ui/views",
     "//ui/views/mus:for_mojo_application",
   ]
@@ skipping 13 matching lines @@
     "//ui/views/mus:for_mojo_application",
   ]
 
   resources = [ "$root_out_dir/views_mus_resources.pak" ]
 }
 
 service_manifest("manifest") {
   name = "task_viewer"
   source = "manifest.json"
 }