Add rudimentary mash shelf functionality.

mash/shelf/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/mojo_application.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 
-mojo_native_application("system_ui") {
+mojo_native_application("shelf") {
   sources = [
     "main.cc",
-    "system_ui.cc",
-    "system_ui.h",
+    "shelf_application.cc",
+    "shelf_application.h",
+    "shelf_view.cc",
+    "shelf_view.h",
   ]
 
   deps = [
     "//base",
     "//components/mus/public/cpp",
     "//components/mus/public/interfaces",
     "//mash/wm/public/interfaces",
     "//mojo/common:common_base",
     "//mojo/services/tracing/public/cpp",
     "//mojo/shell/public/cpp",
     "//skia",
     "//ui/aura",
     "//ui/views",
     "//ui/views/mus:for_mojo_application",
   ]
 
   resources = [ "$root_out_dir/views_mus_resources.pak" ]
 
   data_deps = [
     "//components/mus",
   ]
 }