<!DOCTYPE html>
<html>
<head>
  <style type="text/css">
    .box {
      height: 50px;
      width: 300px;
      margin: 10px;
      background-image: -webkit-linear-gradient(black, black);
      border-radius: 25px;
      border: 4px solid green;
      -webkit-transform: scale(0.25);
    }
  </style>
</head>
<body>
  <!-- You should see no red leaking through the inner edge of the border. -->
  <div style="background-color: red; height: 60px; width: 310px">
    <div class="box"></div>
  </div>
</body>
</html>