[Sync] Move SyncBackendRegistrar to engine/

components/sync/BUILD.gn

Index: components/sync/BUILD.gn
diff --git a/components/sync/BUILD.gn b/components/sync/BUILD.gn
index cad00ffe0493ff40d8f497e5baecb35d1d6a533d..b3b524c7e570d73b63a6786681adcb48552e33d4 100644
--- a/components/sync/BUILD.gn
+++ b/components/sync/BUILD.gn
@@ -126,8 +126,6 @@ static_library("sync") {
     "driver/glue/sync_backend_host_core.h",
     "driver/glue/sync_backend_host_impl.cc",
     "driver/glue/sync_backend_host_impl.h",
-    "driver/glue/sync_backend_registrar.cc",
-    "driver/glue/sync_backend_registrar.h",
     "driver/model_association_manager.cc",
     "driver/model_association_manager.h",
     "driver/model_associator.h",
@@ -237,6 +235,8 @@ static_library("sync") {
     "engine/polling_constants.h",
     "engine/shutdown_reason.h",
     "engine/sync_auth_provider.h",
+    "engine/sync_backend_registrar.cc",
+    "engine/sync_backend_registrar.h",
     "engine/sync_encryption_handler.cc",
     "engine/sync_encryption_handler.h",
     "engine/sync_engine.cc",
@@ -856,7 +856,6 @@ source_set("unit_tests") {
     "driver/frontend_data_type_controller_unittest.cc",
     "driver/generic_change_processor_unittest.cc",
     "driver/glue/sync_backend_host_impl_unittest.cc",
-    "driver/glue/sync_backend_registrar_unittest.cc",
     "driver/model_association_manager_unittest.cc",
     "driver/model_type_controller_unittest.cc",
     "driver/shared_change_processor_unittest.cc",
@@ -873,6 +872,7 @@ source_set("unit_tests") {
     "engine/cycle/sync_cycle_snapshot_unittest.cc",
     "engine/model_safe_worker_unittest.cc",
     "engine/net/http_bridge_unittest.cc",
+    "engine/sync_backend_registrar_unittest.cc",
     "engine/ui_model_worker_unittest.cc",
     "engine_impl/apply_control_data_updates_unittest.cc",
     "engine_impl/attachments/attachment_downloader_impl_unittest.cc",