third_party/WebKit/LayoutTests/fast/canvas/canvas-filter-units-em.html

<canvas id="canvas" width="100" height="100"></canvas>
<script>
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
ctx.font = '20px sans-serif';
ctx.filter = 'drop-shadow(0em .5em black)';
ctx.fillStyle = '#0f0';
ctx.fillRect(25, 25, 25, 40);
canvas.style.fontSize = '5px';
ctx.font = '4em sans-serif';
ctx.filter = 'drop-shadow(0em .5em black)';
ctx.fillRect(50, 25, 25, 40);
</script>