Hi NOTA,
Well the example you gave doesn't use the webview as far as I can see it.
"
To embed a web page in your app, add the webview tag to your app's embedder page (this is the app page that will display the guest content). In its simplest form, the webview tag includes the src of the web page and css styles that control the appearance of the webview container:
<webview id="foo" src="
http://www.google.com/" style="width:640px; height:480px"></webview>
"
I've tried that webview container but it doesn't work. I might be doing something wrong because I never used it before.
Existing Extensions can't be used as they use different software languages.