I think a lot of web app need to be an native app more than a browser tab. And they were all responsive enough to be contained in a WebView. But repeating making new projects for each web app was frustrated. This is the reason why I make WebShell. It can help you make the web app you like to be a native OS X app.
Another frustrating thing for me is I did not even know how Cocoa framework works and did not know how to write OS X application. I learn swift-lang and learn about the concepts of Cocoa two days and then made WebShell. So I hope that everyone can make web app to be native app even though you are not (Cocoa) developer. The thing you need is only an Xcode.
I build the first WebShell-based app for JS Bin. You could have a glance of it performance. https://github.com/djyde/WebShell/releases/download/untagged...