Remove the enable_mac_keystone build flag.

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 = [
@@ skipping 51 matching lines @@
     "$root_out_dir/liblzma_decompress.dylib",
     "$root_out_dir/xz",
     "$root_out_dir/xzdec",
     "dirdiffer.sh",
     "dirpatcher.sh",
     "dmgdiffer.sh",
     "pkg-dmg",
     "sign_installer_tools.sh",
   ]
 
-  if (enable_mac_keystone) {
+  if (is_chrome_branded) {
     sources += [ "keystone_install.sh" ]
   }
 
   if (is_chrome_branded) {
     sources += [
       "//chrome/app/theme/google_chrome/mac/app_canary.icns",
       "//chrome/app/theme/google_chrome/mac/document_canary.icns",
       "internal/chrome_canary_dmg_dsstore",
       "internal/chrome_canary_dmg_icon.icns",
       "internal/chrome_dmg_background.png",
       "internal/chrome_dmg_dsstore",
       "internal/chrome_dmg_icon.icns",
       "internal/generate_diffs",
       "internal/generate_dmgs",
       "internal/signing_common.sh",
     ]
   }
 
   outputs = [
     "$_packaging_dir/{{source_file_part}}",
   ]
 }