Prevent duplicate concurrent installs of the same extension

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 983 matching lines @@
         'browser/extensions/extension_special_storage_policy_unittest.cc',
         'browser/extensions/extension_sync_data_unittest.cc',
         'browser/extensions/extension_test_message_listener_unittest.cc',
         'browser/extensions/extension_ui_unittest.cc',
         'browser/extensions/extension_warning_badge_service_unittest.cc',
         'browser/extensions/extension_warning_service_unittest.cc',
         'browser/extensions/extension_web_ui_unittest.cc',
         'browser/extensions/external_policy_loader_unittest.cc',
         'browser/extensions/external_provider_impl_unittest.cc',
         'browser/extensions/external_provider_impl_chromeos_unittest.cc',
+        'browser/extensions/install_tracker_unittest.cc',
         'browser/extensions/favicon_downloader_unittest.cc',
         'browser/extensions/menu_manager_unittest.cc',
         'browser/extensions/pack_extension_unittest.cc',
         'browser/extensions/page_action_controller_unittest.cc',
         'browser/extensions/permissions_updater_unittest.cc',
         'browser/extensions/policy_handlers_unittest.cc',
         'browser/extensions/sandboxed_unpacker_unittest.cc',
         'browser/extensions/shared_module_service_unittest.cc',
         'browser/extensions/standard_management_policy_provider_unittest.cc',
         'browser/extensions/token_cache/token_cache_service_unittest.cc',
@@ skipping 1904 matching lines @@
             'unit_tests.isolate',
           ],
           'sources': [
             'unit_tests.isolate',
           ],
         },
       ],
     }],
   ],  # 'conditions'
 }