Codebase Browser
chromium
Go to App

chromium/chrome/test/data/captive_portal/page511.html 

<html>
<head>
<title>511 HTML Redirect to Fake Login Page</title>
<meta http-equiv="refresh" content="0; url=http://mock.captive.portal.test/login.html">
</head>
<body>
</body>
</html>