chromium/third_party/blink/renderer/core/testing/data/first_party/nested-originA-in-originB.html

<!DOCTYPE html>
<html>
<head>
    <title>Document with a frame from `not-example.test` that frames `example.test`.</title>
</head>
<body>
    <iframe src="http://not-example.test:0/first_party/nested-originA.html"></iframe>
</body>
</html>