Reland of Add rudimentary shelf delegate mus unit test.

ash/mus/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")
 import("//mojo/public/mojo_application.gni")
 import("//mojo/public/mojo_application_manifest.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//tools/grit/repack.gni")
 
@@ skipping 111 matching lines @@
 
 repack("resources_200") {
   sources = [
     "$root_out_dir/ash_test_resources_200_percent.pak",
   ]
   output = "$root_out_dir/ash_resources_200_percent.pak"
   deps = [
     "//ash/resources:ash_test_resources_200_percent",
   ]
 }
+
+source_set("unittests") {
+  testonly = true
+
+  sources = [
+    "shelf_delegate_mus_unittest.cc",
+  ]
+
+  deps = [
+    "//base",
+    "//components/mus/public/interfaces",
+    "//mash/shelf/public/interfaces",
+    "//mojo/public/cpp/bindings",
+    "//services/shell/public/cpp:shell_test_support",
+  ]
+
+  data_deps = [
+    "//mash/session",
+    ":mus",
+  ]
+}