[Sync] USS: Add EntityChange.

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/data_batch.h",
+    "api/entity_change.cc",
+    "api/entity_change.h",
     "api/entity_data.cc",
     "api/entity_data.h",
     "api/metadata_batch.h",
     "api/metadata_changes.h",
     "api/model_type_change_processor.cc",
     "api/model_type_change_processor.h",
     "api/model_type_service.cc",
     "api/model_type_service.h",
     "api/model_type_store.cc",
     "api/model_type_store.h",
@@ skipping 823 matching lines @@
       ":fake_server_jni",
       ":sync_core",
       ":test_support_sync_fake_server",
       "//base",
       "//sync/protocol:protocol",
       "//testing/gtest",
       "//url:url",
     ]
   }
 }