Implement SequenceChecker, which is a generalization of ThreadChecker

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 335 matching lines @@
           'rand_util.h',
           'rand_util_nacl.cc',
           'rand_util_posix.cc',
           'rand_util_win.cc',
           'run_loop.cc',
           'run_loop.h',
           'safe_strerror_posix.cc',
           'safe_strerror_posix.h',
           'scoped_native_library.cc',
           'scoped_native_library.h',
+          'sequence_checker.h',
+          'sequence_checker_impl.cc',
+          'sequence_checker_impl.h',
           'sequenced_task_runner.cc',
           'sequenced_task_runner.h',
           'sequenced_task_runner_helpers.h',
           'sha1.h',
           'sha1_portable.cc',
           'sha1_win.cc',
           'shared_memory.h',
           'shared_memory_android.cc',
           'shared_memory_nacl.cc',
           'shared_memory_posix.cc',
@@ skipping 356 matching lines @@
           # Remove all unnecessary files for build_nexe.py to avoid exceeding
           # command-line-string limitation when building NaCl on Windows.
           ['OS == "win" and >(nacl_untrusted_build)==1', {
               'sources/': [ ['exclude', '\\.h$'] ],
           }],
         ],
       }],
     ],
   },
 }