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

sync/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/features.gni")
 import("//testing/test.gni")
 
 component("sync") {
   public_deps = [
     ":sync_core",
     "//sync/protocol",
   ]
 }
 
 # GYP version: sync/sync.gyp:sync_core
 source_set("sync_core") {
   sources = [
     "api/attachments/attachment.cc",
     "api/attachments/attachment.h",
     "api/attachments/attachment_id.cc",
     "api/attachments/attachment_id.h",
     "api/attachments/attachment_metadata.cc",
     "api/attachments/attachment_metadata.h",
     "api/attachments/attachment_store.cc",
     "api/attachments/attachment_store.h",
-    "api/attachments/attachment_store_backend.cc",
-    "api/attachments/attachment_store_backend.h",
     "api/string_ordinal.h",
     "api/sync_change.cc",
     "api/sync_change.h",
     "api/sync_change_processor.cc",
     "api/sync_change_processor.h",
     "api/sync_data.cc",
     "api/sync_data.h",
     "api/sync_error.cc",
     "api/sync_error.h",
     "api/sync_error_factory.cc",
@@ skipping 80 matching lines @@
     "engine/update_applicator.cc",
     "engine/update_applicator.h",
     "engine/update_handler.cc",
     "engine/update_handler.h",
     "internal_api/attachments/attachment_downloader.cc",
     "internal_api/attachments/attachment_downloader_impl.cc",
     "internal_api/attachments/attachment_service.cc",
     "internal_api/attachments/attachment_service_impl.cc",
     "internal_api/attachments/attachment_service_proxy.cc",
     "internal_api/attachments/attachment_service_proxy_for_test.cc",
-    "internal_api/attachments/attachment_store_frontend.cc",
+    "internal_api/attachments/attachment_store_handle.cc",
     "internal_api/attachments/attachment_uploader.cc",
     "internal_api/attachments/attachment_uploader_impl.cc",
     "internal_api/attachments/attachment_util.cc",
     "internal_api/attachments/fake_attachment_downloader.cc",
     "internal_api/attachments/fake_attachment_uploader.cc",
     "internal_api/attachments/in_memory_attachment_store.cc",
     "internal_api/attachments/on_disk_attachment_store.cc",
     "internal_api/base_node.cc",
     "internal_api/base_transaction.cc",
     "internal_api/change_record.cc",
@@ skipping 19 matching lines @@
     "internal_api/js_sync_manager_observer.cc",
     "internal_api/js_sync_manager_observer.h",
     "internal_api/protocol_event_buffer.cc",
     "internal_api/protocol_event_buffer.h",
     "internal_api/public/attachments/attachment_downloader.h",
     "internal_api/public/attachments/attachment_downloader_impl.h",
     "internal_api/public/attachments/attachment_service.h",
     "internal_api/public/attachments/attachment_service_impl.h",
     "internal_api/public/attachments/attachment_service_proxy.h",
     "internal_api/public/attachments/attachment_service_proxy_for_test.h",
-    "internal_api/public/attachments/attachment_store_frontend.h",
+    "internal_api/public/attachments/attachment_store_handle.h",
     "internal_api/public/attachments/attachment_uploader.h",
     "internal_api/public/attachments/attachment_uploader_impl.h",
     "internal_api/public/attachments/attachment_util.h",
     "internal_api/public/attachments/fake_attachment_downloader.h",
     "internal_api/public/attachments/fake_attachment_uploader.h",
     "internal_api/public/attachments/in_memory_attachment_store.h",
     "internal_api/public/attachments/on_disk_attachment_store.h",
     "internal_api/public/base/attachment_id_proto.cc",
     "internal_api/public/base/attachment_id_proto.h",
     "internal_api/public/base/cancelation_observer.cc",
@@ skipping 388 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/debug_info_event_listener_unittest.cc",
     "internal_api/http_bridge_unittest.cc",
     "internal_api/js_mutation_event_observer_unittest.cc",
     "internal_api/js_sync_encryption_handler_observer_unittest.cc",
@@ skipping 221 matching lines @@
     ]
     deps = [
       ":fake_server_jni",
       ":sync_core",
       ":test_support_sync_fake_server",
       "//base",
       "//testing/gtest",
     ]
   }
 }