m = document.getElementById("thediv");
    elem.style.height = "170px";
    assert_equals(elem.style.height, "170px");

    oldScrollHeight =  document.body.scrollHeight;
    elem.style.height = "190px";
    assert_equals(elem.style.height, "190px");
    assert_equals(document.body.scrollHeight, oldScrollHeight+20);
}, "When body potentially scrollable, document.body.scrollHeight changes when changing the height of the body content in quirks.")

// any use of `visible` => not potentially scrollable
function