Add Widevine signature files for Win into the build

chrome/tools/build/win/FILES.cfg

 # -*- python -*-
 # ex: set syntax=python:
 
 # Copyright (c) 2012 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.
 
 # This is a buildbot configuration file containing a tagged list of files
 # processed by the stage/archive scripts. The known tags are:
 #
@@ skipping 325 matching lines @@
   {
     'filename': 'WidevineCdm/manifest.json',
     'buildtype': ['official'],
   },
   {
     'filename': 'WidevineCdm/_platform_specific/win_x86/widevinecdm.dll',
     'arch': ['32bit'],
     'buildtype': ['official'],
   },
   {
+    'filename': 'WidevineCdm/_platform_specific/win_x86/widevinecdm.dll.sig',
+    'arch': ['32bit'],
+    'buildtype': ['official'],
+  },
+  {
     'filename': 'WidevineCdm/_platform_specific/win_x86/widevinecdmadapter.dll',
     'arch': ['32bit'],
     'buildtype': ['official'],
   },
   {
     'filename': 'WidevineCdm/_platform_specific/win_x64/widevinecdm.dll',
     'arch': ['64bit'],
     'buildtype': ['official'],
   },
   {
+    'filename': 'WidevineCdm/_platform_specific/win_x64/widevinecdm.dll.sig',
+    'arch': ['64bit'],
+    'buildtype': ['official'],
+  },
+  {
     'filename': 'WidevineCdm/_platform_specific/win_x64/widevinecdmadapter.dll',
     'arch': ['64bit'],
     'buildtype': ['official'],
   },
   # ANGLE files:
   {
     'filename': 'D3DCompiler_47.dll',
     'buildtype': ['dev', 'official'],
   },
   {
@@ skipping 365 matching lines @@
     'archive': 'content-shell.zip',
     'optional': ['dev'],
   },
   {
     'filename': 'resources',
     'buildtype': ['dev'],
     'archive': 'content-shell.zip',
     'optional': ['dev'],
   },
 ]