LayoutTests/svg/custom/visibility-override-mask.svg

<svg xmlns="http://www.w3.org/2000/svg"
     xmlns:xlink="http://www.w3.org/1999/xlink">
    <defs>
        <mask id="mymask">
            <rect x="0" y="0" width="100px" height="100px" fill='white'/>
        </mask>
    </defs>

    <rect fill="blue" height="100px" width="100px"/>
    
    <g mask="url(#mymask)" visibility='hidden'>
        <g visibility='visible'>
            <rect x="0" y="0" width="200px" height="200px" fill="red"/>
            <rect visibility="visible" x="0" y="0" width="100px" height="100px" fill="green"/>
        </g>
        <rect x="0" y="0" width="100px" height="100px" fill="red"/>
    </g>
</svg>