Add a BarrierClosure.

base/base.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.
 
 {
   'target_defaults': {
     'variables': {
       'base_target': 0,
     },
     'target_conditions': [
@@ skipping 60 matching lines @@
           'at_exit.h',
           'atomic_ref_count.h',
           'atomic_sequence_num.h',
           'atomicops.h',
           'atomicops_internals_gcc.h',
           'atomicops_internals_mac.h',
           'atomicops_internals_tsan.h',
           'atomicops_internals_x86_gcc.cc',
           'atomicops_internals_x86_gcc.h',
           'atomicops_internals_x86_msvc.h',
+          'barrier_closure.cc',
+          'barrier_closure.h',
           'base_export.h',
           'base_paths.cc',
           'base_paths.h',
           'base_paths_android.cc',
           'base_paths_android.h',
           'base_paths_mac.h',
           'base_paths_mac.mm',
           'base_paths_posix.cc',
           'base_paths_posix.h',
           'base_paths_win.cc',
@@ skipping 795 matching lines @@
           ['<(use_system_nspr)==1 and >(nacl_untrusted_build)==0', {
             'sources/': [
               ['exclude', '^third_party/nspr/'],
             ],
           }],
         ],
       }],
     ],
   },
 }