Migrate mac installer to delegate-driven model

chrome/installer/mac/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/util/branding.gni")
 import("//build/util/version.gni")
 import("//build/config/features.gni")
 
 group("mac") {
   public_deps = [
     ":copies",
     ":make_signers",
-    "app:downloader",
+    "app:mac_installer",
   ]
 }
 
 _packaging_dir = "$root_out_dir/$chrome_product_full_name Packaging"
 
 action("make_signers") {
   visibility = [ ":mac" ]
 
   script = "//build/gn_run_binary.py"
   shell_script = "//chrome/installer/mac/make_signers.sh"
@@ skipping 58 matching lines @@
       "internal/chrome_dmg_dsstore",
       "internal/chrome_dmg_icon.icns",
       "internal/generate_dmgs",
     ]
   }
 
   outputs = [
     "$_packaging_dir/{{source_file_part}}",
   ]
 }