Revert of Remove shell::Loader

services/shell/tests/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("//mojo/public/mojo_application.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//testing/test.gni")
 
 group("tests") {
   testonly = true
   deps = [
     ":mojo_shell_unittests",
   ]
 }
 
 test("mojo_shell_unittests") {
+  sources = [
+    "loader_unittest.cc",
+  ]
+
   deps = [
     ":interfaces",
     "//base",
     "//base/test:test_support",
     "//mojo/public/cpp/bindings",
     "//mojo/public/cpp/system",
     "//mojo/util:filename_util",
     "//services/catalog:unittests",
     "//services/shell",
     "//services/shell/background:lib",
@@ skipping 22 matching lines @@
   ]
   deps = [
     "//base",
     "//base:base_static",
     "//mojo/edk/system",
     "//services/shell/public/cpp:sources",
     "//services/shell/public/interfaces",
     "//services/shell/runner/common",
   ]
 }