How does the 1Password Chrome Extension achieve rounded corners?

There are many (1 2 3) answers on Stackoverflow saying a Chrome extension cannot have rounded corners when opened, and yet... The 1Password extension does.

I've noticed the extension is draggable unlike other extensions, and I've noticed I can't right click and inspect it. I've also noticed that if I drag it very quickly, a 'ghost' extension flickers in the middle of my screen.

Any ideas whats going on?

What you're seeing is not part of the Chrome extension, but the 1Password application itself. The extension merely acts as a middleman between Chrome and the real password manager app on your computer. In fact, the 1Password extension requires the 1Password app to be installed on your computer in order to work. When you click on the icon, that's not a popup window, but a native window created by the 1Password app itself. This is done through native messaging.