Revert of [Sync] Refactor AttachmentStore classes. Introduce concept of referrer.

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.
     # GN version: //sync:test_support_sync_core
     {
       'target_name': 'test_support_sync_core',
@@ skipping 264 matching lines @@
         'engine/model_type_entity_unittest.cc',
         'engine/model_type_sync_proxy_impl_unittest.cc',
         'engine/model_type_sync_worker_impl_unittest.cc',
         'engine/sync_scheduler_unittest.cc',
         'engine/syncer_proto_util_unittest.cc',
         'engine/syncer_unittest.cc',
         'engine/syncer_util_unittest.cc',
         'internal_api/attachments/attachment_downloader_impl_unittest.cc',
         'internal_api/attachments/attachment_service_impl_unittest.cc',
         'internal_api/attachments/attachment_service_proxy_unittest.cc',
-        'internal_api/attachments/attachment_store_frontend_unittest.cc',
+        'internal_api/attachments/attachment_store_handle_unittest.cc',
         'internal_api/attachments/attachment_store_test_template.h',
         'internal_api/attachments/attachment_uploader_impl_unittest.cc',
         'internal_api/attachments/fake_attachment_downloader_unittest.cc',
         'internal_api/attachments/fake_attachment_uploader_unittest.cc',
         'internal_api/attachments/in_memory_attachment_store_unittest.cc',
         'internal_api/attachments/on_disk_attachment_store_unittest.cc',
         'internal_api/attachments/task_queue_unittest.cc',
         'internal_api/debug_info_event_listener_unittest.cc',
         'internal_api/http_bridge_unittest.cc',
         'internal_api/js_mutation_event_observer_unittest.cc',
@@ skipping 199 matching lines @@
           ],
           'variables': {
             'test_suite_name': 'sync_unit_tests',
           },
           'includes': [ '../build/apk_test.gypi' ],
         },
       ],
     }],
   ],
 }