After generating your Web Manifest, get back to the Codelab. Configuring the app.webmanifest file helps you to specify how you want your Web App to look like when launched on the device.
<body>
{ "lang": "en-US", "start_url": "/", "display": "standalone"}
<link rel="manifest" href="manifest.json"><meta name="mobile-web-app-capable" content="yes"><meta name="apple-mobile-web-app-capable" content="yes"><meta name="msapplication-starturl" content="/"><meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<meta>