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chromium/third_party/blink/web_tests/css3/blending/background-blend-mode-body-iframe-transparent-color.html 

<!DOCTYPE HTML>
<style>
    html, body, iframe {
        width: 100%;
        height: 100%;
    }

    body {
        overflow: hidden;
        margin: 0;
    }

    iframe {
        border: none;
    }
</style>

<iframe src="background-blend-mode-body-transparent-color-and-image.html"></iframe>