UserAgent: Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.98 Safari/537.36

Steps to reproduce the problem:
1.just open
2. 
3. 

What is the expected behavior?
would like option for full screen

What went wrong?
nothing

Did this work before? No 

Chrome version: 71.0.3578.98  Channel: stable
OS Version: 6.1 (Windows 7, Windows Server 2008 R2)
Flash Version: .1

this is supposed to work, but can't find

In your extensions "background.js" script:

chrome.app.runtime.onLaunched.addListener(function (launchData) {
  chrome.app.window.create(
    // Url
    '/editor.html',
    // CreateWindowOptions
    {
            'width': 400,
            'height': 500
    },
    // Callback
    function(win) {
        win.contentWindow.launchData = launchData;
        win.maximize();
        win.show();
    });
});