third_party/WebKit/LayoutTests/animations/background-trailing-comma-crash.html

<script src="../resources/testharness.js"></script>
<script src="../resources/testharnessreport.js"></script>
<div id="target"></div>
<script>
test(() => {
  target.animate({background: 'none, 10px'}, {fill: 'forwards'});
  getComputedStyle(target).backgroundPosition;
}, "Don't crash when animating background with implicit longhand values and more than one bg-layer.");
</script>