This feature was added to HTML 5.2 version though, it was removed in the latest draft version because no browsers have not supported this feature. So it would be good if Chrome supports this feature.

- Spec: https://www.w3.org/TR/html52/webappapis.html#dom-navigatorcontentutils-isprotocolhandlerregistered.

- Remove this feature from the spec: https://github.com/whatwg/html/issues/630