absolute-root-position-masking.xhtml

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:svg="http://www.w3.org/2000/svg">
<body style="margin: 0;">
<svg:svg id="svg" width="300" height="300" style="position: absolute; top: 100px; left: 0px;">
    <svg:circle cx="300" cy="300" r="100" fill="blue" mask="url(#mask)"/>
    <svg:defs>
        <svg:pattern id="pattern" width="600" height="600">
            <svg:rect fill="white" width="600" height="600" />
        </svg:pattern>
        <svg:mask id="mask" width="600" height="600">
            <svg:rect fill="url(#pattern)" width="600" height="600" />
        </svg:mask>
    </svg:defs>
</svg:svg>
</body>
</html>

chromium/third_party/blink/web_tests/svg/custom/absolute-root-position-masking.xhtml