[sync] WebContentsObserver based sessions notifications

chrome/browser/BUILD.gn

Index: chrome/browser/BUILD.gn
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 45f0448d66658c7e8c0e78964ded49213b3956fc..55efbf3dd46da6208cbe327cb0894edef5cea026 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -1273,8 +1273,12 @@ split_static_library("browser") {
     "sync/glue/sync_start_util.h",
     "sync/profile_sync_service_factory.cc",
     "sync/profile_sync_service_factory.h",
-    "sync/sessions/notification_service_sessions_router.cc",
-    "sync/sessions/notification_service_sessions_router.h",
+    "sync/sessions/sync_sessions_router_tab_helper.cc",
+    "sync/sessions/sync_sessions_router_tab_helper.h",
+    "sync/sessions/sync_sessions_web_contents_router.cc",
+    "sync/sessions/sync_sessions_web_contents_router.h",
+    "sync/sessions/sync_sessions_web_contents_router_factory.cc",
+    "sync/sessions/sync_sessions_web_contents_router_factory.h",
     "sync/supervised_user_signin_manager_wrapper.cc",
     "sync/supervised_user_signin_manager_wrapper.h",
     "sync/sync_startup_tracker.cc",