#import [Exposed=(Window)] interface ResizeObserver { constructor(ResizeObserverCallback callback); undefined observe(Element target, optional ResizeObserverOptions options = {}); undefined unobserve(Element target); undefined disconnect(); }; callback ResizeObserverCallback = void (sequence entries, ResizeObserver observer); dictionary ResizeObserverOptions { // FIXME: This should be an enum. DOMString box = "content-box"; };