Add preliminary support for UBsan's vptr in Chromium (-fsanitize=vptr).

ppapi/native_client/src/trusted/plugin/plugin.gypi

 # Copyright (c) 2012 The Native Client 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': {
     'chromium_code': 1,  # Use higher warning level.
     'common_sources': [
       'file_downloader.cc',
       'module_ppapi.cc',
@@ skipping 23 matching lines @@
           'XP_UNIX',
           'MOZ_X11',
         ],
         'cflags': [
           '-Wno-long-long',
         ],
         'cflags!': [
           '-Wno-unused-parameter', # be a bit stricter to match NaCl flags.
         ],
         'conditions': [
-          ['asan!=1 and msan!=1', {
+          ['asan!=1 and msan!=1 and ubsan_vptr!=1', {
             'ldflags': [
               # Catch unresolved symbols.
               '-Wl,-z,defs',
             ],
           }],
         ],
         'libraries': [
           '-ldl',
         ],
       }],
@@ skipping 30 matching lines @@
         'link_settings': {
           'libraries': [
             '-lgdi32.lib',
             '-luser32.lib',
           ],
         },
       }],
     ],
   },
 }