Add Widevine signature files into Mac build

third_party/widevine/cdm/BUILD.gn

 # Copyright 2014 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/chrome_build.gni")
 import("//build/config/features.gni")
 import("//chrome/process_version_rc_template.gni")
 import("//media/cdm/ppapi/cdm_paths.gni")
 import("//media/cdm/ppapi/ppapi_cdm_adapter.gni")
 import("//ppapi/features/features.gni")
@@ skipping 23 matching lines @@
     ]
   } else if (is_win) {
     widevine_cdm_version_h_file = "win/$widevine_arch/widevine_cdm_version.h"
     widevine_cdm_binary_files = [
       "win/$widevine_arch/widevinecdm.dll",
       "win/$widevine_arch/widevinecdm.dll.lib",
     ]
     widevine_cdm_manifest_file = [ "win/$widevine_arch/manifest.json" ]
   } else if (is_mac) {
     widevine_cdm_version_h_file = "mac/$widevine_arch/widevine_cdm_version.h"
-    widevine_cdm_binary_files = [ "mac/$widevine_arch/libwidevinecdm.dylib" ]
+    widevine_cdm_binary_files = [
+      "mac/$widevine_arch/libwidevinecdm.dylib",
+      "mac/$widevine_arch/libwidevinecdm.dylib.sig",
+    ]
     widevine_cdm_manifest_file = [ "mac/$widevine_arch/manifest.json" ]
   } else {
     # Other platforms, use the default one.
     widevine_cdm_version_h_file = "widevine_cdm_version.h"
   }
 } else if (enable_widevine) {
   widevine_cdm_version_h_file = "stub/widevine_cdm_version.h"
   widevine_cdm_manifest_file = [ "stub/manifest.json" ]
 } else {
   # No branding, use the default one.
@@ skipping 148 matching lines @@
       "../scripts/signer.py",
     ]
     outputs = [
       "$root_out_dir/installer/widevine/{{source_file_part}}",
     ]
   }
 } else {
   group("widevine_signature_scripts") {
   }
 }