interface HTMLCanvasElement {};
    interface HTMLMediaElement {};
    interface MediaStream {};
    interface MediaStreamTrack {};
  

    // https://w3c.github.io/mediacapture-fromelement/

    partial interface HTMLMediaElement {
        MediaStream captureStream();
    };

    partial interface HTMLCanvasElement {
        MediaStream captureStream(optional double frameRequestRate);
    };

    interface CanvasCaptureMediaStreamTrack : MediaStreamTrack {
        readonly attribute HTMLCanvasElement canvas;
        void requestFrame();
    };