sync: Gracefully handle very early shutdown

sync/sync_tests.gypi

 # Copyright 2013 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': [
     # Test support files for the 'sync_core' target.
     {
       'target_name': 'test_support_sync_core',
       'type': 'static_library',
@@ skipping 208 matching lines @@
         '../testing/gmock.gyp:gmock',
         '../testing/gtest.gyp:gtest',
         'sync',
         'test_support_sync_core',
       ],
       'direct_dependent_settings': {
         'include_dirs': [
           '..',
         ],
         'sources': [
+          'internal_api/public/base/cancelation_signal_unittest.cc',
           'internal_api/public/base/enum_set_unittest.cc',
           'internal_api/public/base/node_ordinal_unittest.cc',
           'internal_api/public/base/ordinal_unittest.cc',
           'internal_api/public/base/unique_position_unittest.cc',
           'internal_api/public/engine/model_safe_worker_unittest.cc',
           'internal_api/public/util/immutable_unittest.cc',
           'internal_api/public/util/weak_handle_unittest.cc',
           'engine/apply_control_data_updates_unittest.cc',
           'engine/apply_updates_and_resolve_conflicts_command_unittest.cc',
           'engine/backoff_delay_provider_unittest.cc',
@@ skipping 389 matching lines @@
           'variables': {
             'test_suite_name': 'sync_unit_tests',
             'input_shlib_path': '<(SHARED_LIB_DIR)/<(SHARED_LIB_PREFIX)sync_unit_tests<(SHARED_LIB_SUFFIX)',
           },
           'includes': [ '../build/apk_test.gypi' ],
         },
       ],
     }],
   ],
 }