chromium/third_party/blink/web_tests/transforms/skew-with-unitless-zero.html

<html>
<head>
<style>
div {
  width:100px;
  height:100px;
  border:10px solid black;
  background-color:skyblue;
  margin:100px;
}

.skew {
  transform:skew(0, 45deg)
}
</style>
</head>
<body>
In the example below you should a y-skewed block (45 degree angle of skew).

<div class="skew"></div>