More user id tracking for mus:

components/mus/ws/BUILD.gn

Index: components/mus/ws/BUILD.gn
diff --git a/components/mus/ws/BUILD.gn b/components/mus/ws/BUILD.gn
index ec8e7024cfe8039095eb7fe8a72bf98e90e5283c..9ad7126fa5d495b68256ef576a0b00d8d741e9c0 100644
--- a/components/mus/ws/BUILD.gn
+++ b/components/mus/ws/BUILD.gn
@@ -44,6 +44,10 @@ source_set("lib") {
     "server_window_surface_manager.cc",
     "server_window_surface_manager.h",
     "server_window_tracker.h",
+    "user_id.h",
+    "user_id_tracker.cc",
+    "user_id_tracker.h",
+    "user_id_tracker_observer.h",
     "window_coordinate_conversions.cc",
     "window_coordinate_conversions.h",
     "window_finder.cc",
@@ -52,6 +56,7 @@ source_set("lib") {
     "window_manager_access_policy.h",
     "window_manager_factory_registry.cc",
     "window_manager_factory_registry.h",
+    "window_manager_factory_registry_observer.h",
     "window_manager_factory_service.cc",
     "window_manager_factory_service.h",
     "window_manager_state.cc",
@@ -83,6 +88,7 @@ source_set("lib") {
     "//mojo/public/cpp/bindings:callback",
     "//mojo/services/tracing/public/cpp",
     "//mojo/shell/public/cpp",
+    "//mojo/shell/public/interfaces",
     "//ui/base",
     "//ui/events",
     "//ui/events/platform",
@@ -139,9 +145,12 @@ test("window_manager_unittests") {
     "server_window_surface_manager_test_api.h",
     "test_server_window_delegate.cc",
     "test_server_window_delegate.h",
+    "test_utils.cc",
+    "test_utils.h",
     "transient_windows_unittest.cc",
     "window_coordinate_conversions_unittest.cc",
     "window_finder_unittest.cc",
+    "window_tree_host_unittest.cc",
     "window_tree_unittest.cc",
   ]