Disable install of new default_apps for existing users

chrome/chrome_tests.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.
 {
   'variables' : {
     'pyautolib_sources': [
       'app/chrome_command_ids.h',
       'app/chrome_dll_resource.h',
       'common/automation_constants.h',
       'common/pref_names.cc',
@@ skipping 1239 matching lines @@
         'browser/extensions/api/web_request/web_request_time_tracker_unittest.cc',
         'browser/extensions/app_notification_manager_sync_unittest.cc',
         'browser/extensions/app_notification_manager_unittest.cc',
         'browser/extensions/app_notification_storage_unittest.cc',
         'browser/extensions/app_notification_test_util.cc',
         'browser/extensions/app_notify_channel_setup_unittest.cc',
         'browser/extensions/app_sync_data_unittest.cc',
         'browser/extensions/component_loader_unittest.cc',
         'browser/extensions/convert_user_script_unittest.cc',
         'browser/extensions/convert_web_app_unittest.cc',
+        'browser/extensions/default_apps_unittest.cc',
         'browser/extensions/event_listener_map_unittest.cc',
         'browser/extensions/event_router_forwarder_unittest.cc',
         'browser/extensions/extension_creator_filter_unittest.cc',
         'browser/extensions/extension_function_test_utils.cc',
         'browser/extensions/extension_function_test_utils.h',
         'browser/extensions/extension_icon_image_unittest.cc',
         'browser/extensions/extension_icon_manager_unittest.cc',
         'browser/extensions/extension_info_map_unittest.cc',
         'browser/extensions/extension_pref_value_map_unittest.cc',
         'browser/extensions/extension_prefs_unittest.cc',
@@ skipping 3460 matching lines @@
                 '--result', '<@(_outputs)',
                 '--isolate', 'browser_tests.isolate',
               ],
             },
           ],
         },
       ],
     }],
   ],  # 'conditions'
 }