chromium/third_party/blink/web_tests/fast/clip/006.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
<html>
<head>
<style>
.green {
  width: 100px;
  height: 100px;
  background-color: green;
  left: 100px;
  top: 70px;
}

.red {
  width: 100px;
  height: 100px;
  margin-top: 100px;
  margin-left: 100px;
  background-color: red;
}

.overflow {
  overflow: hidden;
  width: 100px;
  height: 100px;
}

.positioned {
  position: fixed;
}
</style>
<body>
You should see a 100x100 green square below.  If you see nothing at all or see any red, the test
has failed.  This test is checking to make sure overflow is done using 
a containing block model, and that a fixed positioned element inside another fixed positioned
element is not considered overflow.

<div class="overflow positioned">
<div class="red"></div>
<div class="green positioned"></div>
</div>