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chromium/third_party/blink/web_tests/paint/invalidation/position/absolute-position-and-opacity-changed-expected.html 

<!doctype html>
<style>
div {
  width: 50px;
  height: 50px;
  position: absolute;
  top: 30px;
}
</style>
There should be a single green square below.
<div style="background: red"></div>
<div style="background: green; opacity: 0.9" id="target"></div>