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

ios/web/navigation/navigation_manager_impl.mm

Index: ios/web/navigation/navigation_manager_impl.mm
diff --git a/ios/web/navigation/navigation_manager_impl.mm b/ios/web/navigation/navigation_manager_impl.mm
index a9e42e85157e6e0aab693ee103ae6ee809afc2b3..75061730fa363d02e3b813ba9ae1b5655d47d7a3 100644
--- a/ios/web/navigation/navigation_manager_impl.mm
+++ b/ios/web/navigation/navigation_manager_impl.mm
@@ -170,6 +170,16 @@ bool AreURLsInPageNavigation(const GURL& existing_url, const GURL& new_url) {
   delegate_->GetWebState()->OpenURL(params);
 }
 
+void NavigationManagerImpl::AddTransientItem(const GURL& url) {
+  [session_controller_ addTransientItemWithURL:url];
+  DCHECK(GetTransientItem());
+
+  // Transient item can only be added for pending non-app-specific loads.
+  DCHECK(GetPendingItem());
+  DCHECK(GetPendingItem()->GetUserAgentType() != UserAgentType::NONE);
+  GetTransientItem()->SetUserAgentType(GetPendingItem()->GetUserAgentType());
+}
+
 void NavigationManagerImpl::AddPendingItem(
     const GURL& url,
     const web::Referrer& referrer,