Codebase Browser
chromium
Go to App

chromium/chrome/test/data/web_apps/nesting/nested/diy.html 

<!DOCTYPE html>
<html>
<head>
  <link rel="icon" href="basic-48.png">
  <title>DIY app</title>
</head>
<body>
  <h1>Nested web app, but DIY (no manifest)</h1>
</body>
</html>