StyleSheet];
    assert_equals(getComputedStyle(greenIframeSpan).color, "rgb(0, 0, 0)");
    assert_equals(getComputedStyle(redIframeSpan).color, "rgb(255, 0, 0)");
    assert_equals(getComputedStyle(blueIframeSpan).color, "rgb(0, 0, 0)");
    assert_equals(getComputedStyle(whiteIframeSpan).color, "rgb(0, 0, 0)");
    assert_equals(getComputedStyle(yellowIframeSpan).color, "rgb(0, 0, 0)");

    iframe.contentDocument.adoptedStyleSheets[0].insertRule(redStyleTexts[1]);
    assert_equals(getComputedStyle(gree