<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
   "http://www.w3.org/TR/html4/loose.dtd">

<html lang="en">
<head>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
  <title>Transform Center with Borders</title>
  <style type="text/css" media="screen">
    .container {
      height: 210px;
      width: 400px;
      margin: 30px;
      outline: 5px solid black;
    }
    .box {
      height: 100px;
      width: 200px;
      margin-bottom: 10px;
      background-color: green;
      border-right: 50px solid gray;
      box-sizing: auto;
      -webkit-transform: scalex(2);
      -webkit-transform-origin: left;
    }
    .border-box {
      box-sizing: border-box;
    }
  </style>
</head>
<body>

<p>
<p>Top box should have gray part extending outside the black outline. Lower box should lie inside the outline</p>
  <div class="container">
    <div class="box">box-sizing: auto</div>
    <div class="box border-box">box-sizing: border-box</div>
  </div>
</body>
</html>