Opaque text not always painted

[paulrouget]

This code is supposed to animate text opacity.

Text doesn't show up until opacity reaches 1.

<script>
  setTimeout(() => {
    var div = document.querySelector(".v");
    var i = 0;
    var max = 60;
    function step() {
      if (i < max) {
        requestAnimationFrame(step);
      }
      div.style.opacity = i++ / max;
    }
    step();
  }, 1000);
</script>

<div style="width: 400px; height: 400px; padding-top: 40px; overflow: hidden; ">
  <div class="v" style="opacity: 0">FOOBAR</div>
</div>

[glennw]

Fixed by glennw/servo@9cf324d