Refactor code signing script and template.

components/cronet/ios/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/buildflag_header.gni")
 import("//build/config/ios/rules.gni")
 import("//build/config/mac/symbols.gni")
 import("//build/mac/tweak_info_plist.gni")
 import("//build/util/version.gni")
 import("//chrome/version.gni")
@@ skipping 46 matching lines @@
 
 # Tweak |info_plist| with current version and revision.
 tweak_info_plist("tweak_cronet_plist") {
   info_plist = "Info.plist"
   args = []
 }
 
 ios_framework_bundle("cronet_framework") {
   output_name = "Cronet"
   info_plist_target = ":tweak_cronet_plist"
-  code_signing_enabled = false
 
   deps = [
     ":cronet_sources",
     "//base",
     "//net:net",
   ]
 
   libs = [ "UIKit.Framework" ]
 
   public_headers = [
@@ skipping 94 matching lines @@
     ]
   }
 
   group("cronet_package") {
     deps = [
       ":cronet_package_copy",
       ":generate_license",
     ]
   }
 }