[Sync] Introduce SyncedSessionWindow type.

chrome/browser/ui/webui/foreign_session_handler.cc

Index: chrome/browser/ui/webui/foreign_session_handler.cc
diff --git a/chrome/browser/ui/webui/foreign_session_handler.cc b/chrome/browser/ui/webui/foreign_session_handler.cc
index a20538f62d93aac64164bc7fffba8e2f5ff9caab..d8b1c255e03717dd5e3fe7221673cacb2e64a892 100644
--- a/chrome/browser/ui/webui/foreign_session_handler.cc
+++ b/chrome/browser/ui/webui/foreign_session_handler.cc
@@ -301,7 +301,7 @@ void ForeignSessionHandler::HandleGetForeignSessions(
         // Order tabs by visual order within window.
         for (const auto& window_pair : session->windows) {
           std::unique_ptr<base::DictionaryValue> window_data(
-              SessionWindowToValue(*window_pair.second.get()));
+              SessionWindowToValue(window_pair.second->wrapped_window));
           if (window_data.get())
             window_list->Append(std::move(window_data));
         }