Add a non-blocking "OneShotEvent" class

chrome/chrome_tests_unit.gypi

 # Copyright 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.
 {
   'targets': [
     {
       # This target contains mocks and test utilities that don't belong in
       # production libraries but are used by more than one test executable.
       'target_name': 'test_support_common',
       'type': 'static_library',
@@ skipping 448 matching lines @@
           'conditions': [
             ['incremental_chrome_dll==1', {
               'UseLibraryDependencyInputs': "true",
             }],
           ],
         },
       },
       'sources': [
         '../apps/app_shim/app_shim_host_mac_unittest.cc',
         '../extensions/browser/file_reader_unittest.cc',
+        '../extensions/common/async_event_unittest.cc',
         '../extensions/common/event_filter_unittest.cc',
         '../extensions/common/extension_resource_unittest.cc',
         '../extensions/common/id_util_unittest.cc',
         '../extensions/common/matcher/regex_set_matcher_unittest.cc',
         '../extensions/common/matcher/string_pattern_unittest.cc',
         '../extensions/common/matcher/substring_set_matcher_unittest.cc',
         '../extensions/common/matcher/url_matcher_factory_unittest.cc',
         '../extensions/common/matcher/url_matcher_unittest.cc',
         '../extensions/common/url_pattern_set_unittest.cc',
         '../extensions/common/url_pattern_unittest.cc',
@@ skipping 2036 matching lines @@
               # more details.
               'DebugInformationFormat': '3',
               'ProgramDataBaseFileName': '<(PRODUCT_DIR)/unit_tests.exe.pdb',
             },
           },
         },
       ],
     }],
   ],  # 'conditions'
 }