WebCore/css/fullscreen.css

:-webkit-full-screen {
    position:fixed;
    top:0;
    left:0;
    right:0;
    bottom:0;
}

:root:full-screen-document:not(:full-screen) {
    overflow:hidden;
}

video:-webkit-full-screen {
    width: 100%;
    height: 100%
    image-fit: fill;
}

img:-webkit-full-screen {
    width: 100%;
    height: 100%;
    image-fit: fill;
}

video:-webkit-full-page-media:-webkit-full-screen::-webkit-media-controls-panel {
    bottom: 0px;
}