Remove fullscreen window decoration/border Chrome OS app/kiosk mode
In Chromium, the <body> tag has a default margin of 8 pixels. If you want to dedicate all space to the webview, make sure that the margin is 0, by using the following stylesheet:
html, body, webview { margin: 0; padding: 0; border: 0; display: block; width: 100%; height: 100%;}