Return Windows error code when create-process fails.

chrome/installer/mini_installer.gypi

 # 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.
 {
   'dependencies': [
     '<@(chrome_dll_project)',
     '../chrome.gyp:chrome',
     '../chrome.gyp:chrome_nacl_win64',
     '../chrome.gyp:default_extensions',
     '../chrome.gyp:setup',
@@ skipping 17 matching lines @@
     'mini_installer/mini_installer.ico',
     'mini_installer/mini_installer.rc',
     'mini_installer/mini_installer_constants.cc',
     'mini_installer/mini_installer_constants.h',
     'mini_installer/mini_installer_exe_version.rc.version',
     'mini_installer/mini_installer_resource.h',
     'mini_installer/mini_string.cc',
     'mini_installer/mini_string.h',
     'mini_installer/pe_resource.cc',
     'mini_installer/pe_resource.h',
+    'mini_installer/regkey.cc',
+    'mini_installer/regkey.h',
   ],
   # Disable precompiled headers for this project, to avoid
   # linker errors when building with VS 2008.
   'msvs_precompiled_header': '',
   'msvs_precompiled_source': '',
   'msvs_settings': {
     'VCCLCompilerTool': {
       'EnableIntrinsicFunctions': 'true',
       'BufferSecurityCheck': 'false',
       'BasicRuntimeChecks': '0',
@@ skipping 191 matching lines @@
       'variables': {
          'branding_dir': '../app/theme/chromium',
       },
     }],
     ['OS=="win" and buildtype=="Official"', {
       # Optimize for size when doing an official build.
       'optimize' :'size',
     }],
   ],
 }