chromium/src/third_party/blink/web_tests/fast/canvas/canvas-filter-units-em-liveness.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 1em green)';
ctx.font = '5px sans-serif';
ctx.fillStyle = 'green';
ctx.fillRect(25, 25, 25, 30);
ctx.font = '10px sans-serif';
ctx.fillRect(60, 25, 25, 30);
</script>