[ios] Correctly determine last seen WKNavigation object.

ios/web/BUILD.gn

Index: ios/web/BUILD.gn
diff --git a/ios/web/BUILD.gn b/ios/web/BUILD.gn
index 27ea4382ace688cbd1f7a92c38042b5230280777..fb5343b26c90637b7112fc5a1594ce56ba7f67a8 100644
--- a/ios/web/BUILD.gn
+++ b/ios/web/BUILD.gn
@@ -207,6 +207,8 @@ source_set("web_arc") {
     "web_state/ui/crw_swipe_recognizer_provider.h",
     "web_state/ui/crw_touch_tracking_recognizer.h",
     "web_state/ui/crw_touch_tracking_recognizer.mm",
+    "web_state/ui/crw_wk_navigation_states.h",
+    "web_state/ui/crw_wk_navigation_states.mm",
     "web_thread_impl.cc",
     "web_thread_impl.h",
     "web_view_creation_util.mm",
@@ -540,6 +542,7 @@ test("ios_web_unittests") {
     "web_state/ui/crw_web_controller_container_view_unittest.mm",
     "web_state/ui/crw_web_controller_observer_unittest.mm",
     "web_state/ui/crw_web_controller_unittest.mm",
+    "web_state/ui/crw_wk_navigation_states_unittest.mm",
     "web_state/ui/crw_wk_script_message_router_unittest.mm",
     "web_state/ui/web_view_js_utils_unittest.mm",
     "web_state/ui/wk_back_forward_list_item_holder_unittest.mm",