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chromium/third_party/blink/web_tests/printing/print-no-background.html 

<!DOCTYPE html>
<script>
    if (window.testRunner)
        testRunner.setPrinting();
</script>
<style>
body {
    background-color: red;
}
</style>
<html>
<body>
    This test succeed if root background is correctly ignored in printing mode.
</body>
</html>