[Sync] Move sync's ModelSafeWorker implementations to engine/.

components/sync/BUILD.gn

Index: components/sync/BUILD.gn
diff --git a/components/sync/BUILD.gn b/components/sync/BUILD.gn
index 5bd464d93c83266265ed29ac31912f45aae9e144..28e1a0eb3bf9122e94b878b75405aef583041c55 100644
--- a/components/sync/BUILD.gn
+++ b/components/sync/BUILD.gn
@@ -122,8 +122,6 @@ static_library("sync") {
     "driver/generic_change_processor.h",
     "driver/generic_change_processor_factory.cc",
     "driver/generic_change_processor_factory.h",
-    "driver/glue/browser_thread_model_worker.cc",
-    "driver/glue/browser_thread_model_worker.h",
     "driver/glue/sync_backend_host.cc",
     "driver/glue/sync_backend_host.h",
     "driver/glue/sync_backend_host_core.cc",
@@ -132,8 +130,6 @@ static_library("sync") {
     "driver/glue/sync_backend_host_impl.h",
     "driver/glue/sync_backend_registrar.cc",
     "driver/glue/sync_backend_registrar.h",
-    "driver/glue/ui_model_worker.cc",
-    "driver/glue/ui_model_worker.h",
     "driver/model_association_manager.cc",
     "driver/model_association_manager.h",
     "driver/model_associator.h",
@@ -194,6 +190,8 @@ static_library("sync") {
     "engine/attachments/in_memory_attachment_store.h",
     "engine/attachments/on_disk_attachment_store.cc",
     "engine/attachments/on_disk_attachment_store.h",
+    "engine/browser_thread_model_worker.cc",
+    "engine/browser_thread_model_worker.h",
     "engine/commit_queue.cc",
     "engine/commit_queue.h",
     "engine/configure_reason.h",
@@ -255,6 +253,8 @@ static_library("sync") {
     "engine/sync_status.h",
     "engine/sync_string_conversions.cc",
     "engine/sync_string_conversions.h",
+    "engine/ui_model_worker.cc",
+    "engine/ui_model_worker.h",
     "engine_impl/all_status.cc",
     "engine_impl/all_status.h",
     "engine_impl/apply_control_data_updates.cc",
@@ -854,10 +854,8 @@ source_set("unit_tests") {
     "driver/data_type_manager_impl_unittest.cc",
     "driver/frontend_data_type_controller_unittest.cc",
     "driver/generic_change_processor_unittest.cc",
-    "driver/glue/browser_thread_model_worker_unittest.cc",
     "driver/glue/sync_backend_host_impl_unittest.cc",
     "driver/glue/sync_backend_registrar_unittest.cc",
-    "driver/glue/ui_model_worker_unittest.cc",
     "driver/model_association_manager_unittest.cc",
     "driver/model_type_controller_unittest.cc",
     "driver/non_ui_data_type_controller_unittest.cc",
@@ -872,9 +870,11 @@ source_set("unit_tests") {
     "engine/attachments/fake_attachment_uploader_unittest.cc",
     "engine/attachments/in_memory_attachment_store_unittest.cc",
     "engine/attachments/on_disk_attachment_store_unittest.cc",
+    "engine/browser_thread_model_worker_unittest.cc",
     "engine/cycle/sync_cycle_snapshot_unittest.cc",
     "engine/model_safe_worker_unittest.cc",
     "engine/net/http_bridge_unittest.cc",
+    "engine/ui_model_worker_unittest.cc",
     "engine_impl/apply_control_data_updates_unittest.cc",
     "engine_impl/attachments/attachment_downloader_impl_unittest.cc",
     "engine_impl/attachments/attachment_uploader_impl_unittest.cc",