Create LibDispatchTaskRunner, a SingleThreadTaskRunner that is backed by a libdispatch queue.

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 191 matching lines @@
           'mac/bind_objc_block.mm',
           'mac/bundle_locations.h',
           'mac/bundle_locations.mm',
           'mac/cocoa_protocols.h',
           'mac/crash_logging.h',
           'mac/crash_logging.mm',
           'mac/foundation_util.h',
           'mac/foundation_util.mm',
           'mac/launchd.cc',
           'mac/launchd.h',
+          'mac/libdispatch_task_runner.cc',
+          'mac/libdispatch_task_runner.h',
           'mac/mac_logging.h',
           'mac/mac_logging.cc',
           'mac/mac_util.h',
           'mac/mac_util.mm',
           'mac/objc_property_releaser.h',
           'mac/objc_property_releaser.mm',
           'mac/os_crash_dumps.cc',
           'mac/os_crash_dumps.h',
           'mac/scoped_aedesc.h',
           'mac/scoped_authorizationref.h',
@@ skipping 495 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$'] ],
           }],
         ],
       }],
     ],
   },
 }