Chrome Version       : 66.0.3359.181
OS Version: 6.1 (Windows 7, Windows Server 2008 R2)
URLs (if applicable) : https://projectclean.herokuapp.com/
Other browsers tested:
  Add OK or FAIL after other browsers where you have tested this issue:
     Safari: OK
    Firefox: OK
    IE/Edge: OK
cc dominickn@chromium.org

What steps will reproduce the problem?
1. Open the website in android chrome.
2. The banner suggesting to add the app to homescreen doesn't appears
3. The 'beforeinstallprompt' doesn't fires automatically

I went through the manual
https://developers.google.com/web/fundamentals/engage-and-retain/app-install-banners/#testing-the-app-install-banner

Have fulfilled the conditions

1)   Manifest file
    {
    "name": "Project clean as pwa",
    "short_name": "Pro Clean",
    "icons":[
    {
    "src": "/icons/icons8-washing-machine-48.png",
    "type": "image/png",
    "sizes": "48x48"
    },
    {
    "src": "/icons/icons8-washing-machine-96.png",
    "type": "image/png",
    "sizes": "96x96"
    },
    {
    "src": "/icons/app-icon-192x192.png",
    "type": "image/png",
    "sizes": "192x192"
    },
    {
    "src": "/icons/icons8-washing-machine-480.png",
    "type": "image/png",
    "sizes": "480x480"
    },
    {
    "src": "/icons/icons8-washing-machine-512.png",
    "type": "image/png",
    "sizes": "512x512"
    }
    ],
    "start_url":"/initial",
    "scope": "../",
    "display":"standalone",
    "orientation":"any",
    "background_color":"#fff",
    "theme_color":"#3f51b5",
    "description":"Simple dry clean description",
    "dir":"ltr",
    "lang":"en-US"
    }

2)   Registered service worker- src/js/application.js
    if("serviceWorker" in navigator){
    navigator.serviceWorker.register('/sw.js')
    .then(function(){
    console.log("Service worker registered");
    });
    };

3)    Added fetch event handler in serviceworker file- /sw.js
    self.addEventListener("fetch",function(event){
    event.respondWith(fetch(event.request));
    });

4)   Saving beforeinstallprompt event for later use - src/js/application.js
    window.addEventListener("beforeinstallprompt",function(event){
    console.log("beforeinstallprompt fired");//this never appears after waiting for long
    event.preventDefault();
    event.prompt();
    deferredPrompt = event;
    return false;
    });

5)    Using the event late. Gets called on clicking 'Collect' button present in /initial- 	src/js/collection.js
    function collectOrder(){
    console.log("Using the event ", deferredPrompt);//on call of the funtion the event comes undefined
    if(deferredPrompt){
    deferredPrompt.prompt();

     deferredPrompt.userChoice.then(function(choiceResult){
     	console.log(choiceResult.outcome);
     	if(choiceResult.outcome==="dismissed")
     		console.log("User cancelled installation");
     	else
     		console.log("User added to homescreen");
     });
     deferredPrompt = null;

    };
    }

6)    The lighthouse test says the app is pass for "install banner"


What is the expected result? The banner should appear.


What happens instead of that? The banner never appeared.


Please provide any additional information below. Attach a screenshot if
possible.

UserAgentString: Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.181 Safari/537.36