Implement use_cfi_cast to optionally enable cast checks.

base/base.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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'includes': [
     '../build/win_precompile.gypi',
@@ skipping 621 matching lines @@
         '../testing/gtest.gyp:gtest',
         '../third_party/icu/icu.gyp:icui18n',
         '../third_party/icu/icu.gyp:icuuc',
       ],
       'includes': ['../build/nocompile.gypi'],
       'variables': {
          # TODO(ajwong): Is there a way to autodetect this?
         'module_dir': 'base'
       },
       'conditions': [
+        ['cfi_vptr==1 and cfi_cast==1', {
+          'defines': [
+             # TODO(krasin): remove CFI_CAST_CHECK, see https://crbug.com/626794.
+            'CFI_CAST_CHECK',
+          ],
+        }],
         ['OS == "ios" or OS == "mac"', {
           'dependencies': [
             'base_unittests_arc',
           ],
         }],
         ['OS == "android"', {
           'dependencies': [
             'android/jni_generator/jni_generator.gyp:jni_generator_tests',
             '../testing/android/native_test.gyp:native_test_native_code',
           ],
@@ skipping 1134 matching lines @@
                 ['include', 'mac/bind_objc_block_unittest_arc\\.mm$'],
                 ['include', 'mac/scoped_nsobject_unittest_arc\\.mm$'],
               ],
             }]
           ],
         },
       ],
     }],
   ],
 }