Revert of Remove shell::Loader

services/shell/BUILD.gn

 # Copyright 2014 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_manifest.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//testing/test.gni")
 
 group("all") {
   testonly = true
   deps = [
     ":shell",
     "//services/shell/background",
     "//services/shell/runner",
     "//services/shell/standalone",
     "//services/shell/tests",
   ]
 }
 
 source_set("shell") {
   output_name = "mojo_shell"
   sources = [
     "connect_params.cc",
     "connect_params.h",
     "connect_util.cc",
     "connect_util.h",
+    "loader.h",
     "native_runner.h",
     "native_runner_delegate.h",
     "shell.cc",
     "shell.h",
     "switches.cc",
     "switches.h",
   ]
 
   deps = [
     "//base",
     "//base/third_party/dynamic_annotations",
     "//mojo/common",
     "//mojo/public/cpp/bindings",
     "//mojo/util:filename_util",
     "//services/catalog/public/interfaces",
     "//services/shell/public/cpp:sources",
     "//services/shell/public/interfaces",
     "//url",
   ]
 
   public_deps = [
     # ApplicationManager exposes and uses PackageManager types in its header.
     "//services/catalog:lib",
   ]
 
   data_deps = [
     ":manifest",
   ]
+
+  # For services/shell/loader.h
+  allow_circular_includes_from = [ "//services/catalog:lib" ]
 }
 
 mojo_application_manifest("manifest") {
   application_name = "shell"
   source = "manifest.json"
 }