[Sync] SyncEngine refactor part 1: interfaces.

components/sync/BUILD.gn

Index: components/sync/BUILD.gn
diff --git a/components/sync/BUILD.gn b/components/sync/BUILD.gn
index 90801bc5471d18795cda65a27d4d9eb3aa4f8c1a..7bd9e26d05db3097278b0cb723069d4cace7e09f 100644
--- a/components/sync/BUILD.gn
+++ b/components/sync/BUILD.gn
@@ -99,8 +99,6 @@ static_library("sync") {
     "device_info/local_device_info_provider_impl.h",
     "driver/about_sync_util.cc",
     "driver/about_sync_util.h",
-    "driver/backend_data_type_configurer.cc",
-    "driver/backend_data_type_configurer.h",
     "driver/backend_migrator.cc",
     "driver/backend_migrator.h",
     "driver/data_type_controller.cc",
@@ -122,8 +120,6 @@ static_library("sync") {
     "driver/generic_change_processor.h",
     "driver/generic_change_processor_factory.cc",
     "driver/generic_change_processor_factory.h",
-    "driver/glue/sync_backend_host.cc",
-    "driver/glue/sync_backend_host.h",
     "driver/glue/sync_backend_host_core.cc",
     "driver/glue/sync_backend_host_core.h",
     "driver/glue/sync_backend_host_impl.cc",
@@ -154,8 +150,6 @@ static_library("sync") {
     "driver/sync_driver_switches.h",
     "driver/sync_error_controller.cc",
     "driver/sync_error_controller.h",
-    "driver/sync_frontend.cc",
-    "driver/sync_frontend.h",
     "driver/sync_service.cc",
     "driver/sync_service.h",
     "driver/sync_service_observer.cc",
@@ -222,6 +216,8 @@ static_library("sync") {
     "engine/events/protocol_event_observer.h",
     "engine/model_safe_worker.cc",
     "engine/model_safe_worker.h",
+    "engine/model_type_configurer.cc",
+    "engine/model_type_configurer.h",
     "engine/model_type_connector.cc",
     "engine/model_type_connector.h",
     "engine/model_type_processor.cc",
@@ -245,6 +241,10 @@ static_library("sync") {
     "engine/sync_auth_provider.h",
     "engine/sync_encryption_handler.cc",
     "engine/sync_encryption_handler.h",
+    "engine/sync_engine.cc",
+    "engine/sync_engine.h",
+    "engine/sync_engine_host.cc",
+    "engine/sync_engine_host.h",
     "engine/sync_manager.cc",
     "engine/sync_manager.h",
     "engine/sync_manager_factory.cc",
@@ -798,14 +798,14 @@ static_library("test_support_driver") {
     "driver/fake_sync_service.h",
     "driver/frontend_data_type_controller_mock.cc",
     "driver/frontend_data_type_controller_mock.h",
-    "driver/glue/sync_backend_host_mock.cc",
-    "driver/glue/sync_backend_host_mock.h",
     "driver/model_associator_mock.cc",
     "driver/model_associator_mock.h",
     "driver/non_ui_data_type_controller_mock.cc",
     "driver/non_ui_data_type_controller_mock.h",
     "driver/sync_api_component_factory_mock.cc",
     "driver/sync_api_component_factory_mock.h",
+    "engine/fake_sync_engine.cc",
+    "engine/fake_sync_engine.h",
     "model/change_processor_mock.cc",
     "model/change_processor_mock.h",
   ]