[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 9ab4837d9ce8d51652e7a5cebeef149e53d16064..20c586eb6d37f25314577fa8b9c8b9c54ced9876 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -1279,8 +1279,12 @@ 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",
@@ -1640,6 +1644,10 @@ split_static_library("browser") {
       "//net:net",
       "//ui/vector_icons",
     ]
+    sources += [
+      "sync/sessions/browser_list_router_helper.cc",
+      "sync/sessions/browser_list_router_helper.h",
+    ]
   }
 
   if (is_chromeos && use_cras) {