[Mac/GN] Add a BUILD.gn file for //chrome/app_shim.

chrome/app_shim/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/mac/rules.gni")
+
 # This is the part of the shim process compiled into Chrome. It runs only
 # in the shim process, after the shim finds and loads the Chrome
 # Framework bundle.
 source_set("app_shim") {
   sources = [
     "chrome_main_app_mode_mac.mm",
   ]
 
   deps = [
     "//chrome:strings",
     "//chrome/common:app_mode_app_support",
   ]
 }
+
+mac_app_bundle("app_mode_loader") {
+  extra_configs = [ "//build/config/compiler:wexit_time_destructors" ]
+
+  info_plist = "app_mode-Info.plist"
+
+  sources = [
+    "app_mode_loader_mac.mm",
+  ]
+
+  deps = [
+    "//chrome/common:app_mode_app_support",
+  ]
+
+  # TODO(rsesek): extra_substitutions = [ APP_MODE_APP_BUNDLE_ID ... ]
+
+  libs = [
+    "CoreFoundation.framework",
+    "Foundation.framework",
+  ]
+}