position-relative-percentage-top-001.html

<!DOCTYPE html>
<title>CSS Flexbox: Relative position with a percentage top</title>
<link rel="help" href="https://drafts.csswg.org/css-flexbox/#valdef-align-items-stretch">
<meta name="assert" content="This test ensures that a flexbox with 'flex-flow: row wrap' properly centers a grandchild with 'position: relative' and 'top: 50%'.">
<style>
html, body {
  margin: 0;
}

.border {
  border:1px solid #000;
}
.width-50 {
  width: 50%;
}
.flex {
  display: flex;
  flex-flow: row wrap;
}
.tall {
  height: 300px;
}
.top-50 {
  position: relative;
  top: 50%;
}
</style>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/check-layout-th.js"></script>
<body onload="checkLayout('.border')">
<div class="border">
  <div class="flex">
    <div class="width-50">
      <label class="top-50" data-offset-y="151">This should be in the center of the container</label>
    </div>
    <div class="width-50">
      <div class="tall">
        This is tall
      </div>
    </div>
  </div>
</div>

chromium/third_party/blink/web_tests/external/wpt/css/css-flexbox/position-relative-percentage-top-001.html