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chromium/third_party/blink/web_tests/printing/standards-percentage-heights.html 

<!DOCTYPE html>
<html style="overflow: hidden; height: 500px; width: 500px; border: 5px solid pink">
<script>
if (window.testRunner)
    testRunner.setPrinting();
</script>
<body style="margin: 0; height: 50%; width: 50%; border: 5px solid salmon;"></body>