I don't see a way to make it happen, either. But it seems crazy to me that browsers can be adding so much OS-like functionality that's a risk to security or privacy without even attempting to bundle them under a "web app" permission to simplify the user experience of opting in to allowing a domain to do all the things a simple web page doesn't need.

And it's absurd that there's seemingly no way for a Chrome user—even with extensions—to prevent a web page from restyling scrollbars into something unrecognizable.