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chromium/third_party/blink/web_tests/paint/invalidation/opacity-from-zero-to-non-zero.html 

<!DOCTYPE html>
<div id="target" style="width: 100px; height: 100px; background: green; opacity: 0"></div>
<script src="resources/text-based-repaint.js"></script>
<script>
function repaintTest() {
  target.style.opacity = 0.5;
};
onload = runRepaintAndPixelTest;
</script>