Enable -Wextra-tokens on win clang.

remoting/remoting_host_win.gypi

 # 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.
 
 {
   'variables': {
     'remoting_host_installer_win_roots': [
       'host/installer/win/',
     ],
     'remoting_host_installer_win_files': [
@@ skipping 12 matching lines @@
         'remoting_host',
       ],
       'sources': [
         'tools/breakpad_tester_win.cc',
       ],
     },  # end of target 'remoting_breakpad_tester'
     {
       # GN version: //remoting/host:remoting_lib_idl
       'target_name': 'remoting_lib_idl',
       'type': 'static_library',
+      'variables': {
+        'clang_warning_flags': [
+          # MIDL generates code like "#endif !_MIDL_USE_GUIDDEF_"
+          '-Wno-extra-tokens',
+        ],
+      },
       'sources': [
         'host/win/chromoting_lib_idl.templ',
         '<(SHARED_INTERMEDIATE_DIR)/remoting/host/chromoting_lib.h',
         '<(SHARED_INTERMEDIATE_DIR)/remoting/host/chromoting_lib.idl',
         '<(SHARED_INTERMEDIATE_DIR)/remoting/host/chromoting_lib_i.c',
       ],
       # This target exports a hard dependency because dependent targets may
       # include chromoting_lib.h, a generated header.
       'hard_dependency': 1,
       'msvs_settings': {
@@ skipping 590 matching lines @@
 
         {
           'target_name': 'remoting_me2me_host_archive',
           'type': 'none',
         },
       ],  # end of 'targets'
     }],  # 'wix_exists == "True" and sas_dll_exists == "True"'
 
   ],  # end of 'conditions'
 }