<!DOCTYPE html>

<html>
<head>
    <style>
        .box {
          width: 100px;
          height: 100px;
          background-color: blue;
        }
        
        .composited {
          -webkit-transform: translateZ(0);
        }

        .masked {
            -webkit-mask-image: linear-gradient(black, transparent);
        }
    </style>
</head>
<body>
<div id="box" class="masked composited box">
</div>
</body>
</html>