Set user agent type of transient item the same as pending item.

ios/web/navigation/navigation_manager_impl.h

Index: ios/web/navigation/navigation_manager_impl.h
diff --git a/ios/web/navigation/navigation_manager_impl.h b/ios/web/navigation/navigation_manager_impl.h
index 9a4298674b0861990db2f5e3f10c384d424388be..f4bb6927b4c116757f1295336dc7e8c12b9376db 100644
--- a/ios/web/navigation/navigation_manager_impl.h
+++ b/ios/web/navigation/navigation_manager_impl.h
@@ -95,6 +95,10 @@ class NavigationManagerImpl : public NavigationManager {
                const Referrer& referrer,
                ui::PageTransition type);
 
+  // Adds a transient item with the given URL. A transient item will be
+  // discarded on any navigation.
+  void AddTransientItem(const GURL& url);
+
   // Adds a new item with the given url, referrer, navigation type, and
   // initiation type, making it the pending item. If pending item is the same as
   // the current item, this does nothing. |referrer| may be nil if there isn't