<!DOCTYPE html>
<meta name="viewport" content="width=device-width,initial-scale=1">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="./resources/intersection-observer-test-utils.js"></script>

<style>
pre, #log {
  position: absolute;
  top: 0;
  left: 200px;
}
iframe {
  width: 180px;
  height: 100px;
}
</style>

<iframe id="iframe" srcdoc="<div id='target' style='margin:0.5px;width:1000px;height:1000px;'></div>"></iframe>

<script>
var 