Enable -Wextra-tokens on win clang.

google_update/google_update.gyp

 # 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.
 
 {
   'targets': [
     {
       'target_name': 'google_update',
       'type': 'static_library',
+      'variables': {
+        'clang_warning_flags': [
+          # MIDL generates code like "#endif !_MIDL_USE_GUIDDEF_"
+          '-Wno-extra-tokens',
+        ],
+      },
       'sources': [
         'google_update_idl.idl',
         '<(SHARED_INTERMEDIATE_DIR)/google_update/google_update_idl.h',
         '<(SHARED_INTERMEDIATE_DIR)/google_update/google_update_idl_i.c',
       ],
       # This target exports a hard dependency because dependent targets may
       # include google_update_idl.h, a generated header.
       'hard_dependency': 1,
       'msvs_settings': {
         'VCMIDLTool': {
           'OutputDirectory': '<(SHARED_INTERMEDIATE_DIR)/google_update',
         },
       },
       'direct_dependent_settings': {
         'include_dirs': [
           '<(SHARED_INTERMEDIATE_DIR)',
         ],
       },
     },
   ],
 }