<window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul" xmlns:html="http://www.w3.org/1999/xhtml" class="reftest-wait"> <script type="text/javascript"><![CDATA[ function run() { const XUL_NS = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"; const HTML_NS = "http://www.w3.org/1999/xhtml"; var span = document.getElementsByTagNameNS(HTML_NS, "span")[0]; span.parentNode.removeChild(span); setTimeout(finish, 0); } function finish() { document.documentElement.removeAttribute("class"); } function load(event) { setTimeout(run, 0); } window.addEventListener("load", load, false); ]]></script> <html:span style="display:inline" flex="1" /> <!-- causes block wrapping --> <box flex="1" /> <label value="hello world" /> </window>