[Mac/GN] Move the bundle ID and creator code into the BRANDING file, and use it.

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")
+import("//build/util/branding.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"
+  extra_substitutions = [ "APP_MODE_APP_BUNDLE_ID=$chrome_mac_bundle_id.app.@APP_MODE_SHORTCUT_ID@" ]
 
   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",
   ]
 }