 testNotPotScrollable (document_overflow, body_overflow) {
    document.body.style.overflowY = body_overflow;
    assert_equals(document.body.style.overflowY, body_overflow);
    document.documentElement.style.overflowY = document_overflow;
    assert_equals(document.documentElement.style.overflowY, document_overflow);

    assert_greater_than(window.innerHeight, 400, "Window not large enough for valid test run.");
    assert_equals(document.body.scrollHeight, window.innerHeight);

    var elem = document.g