<!doctype html>
<html class="reftest-wait">
  <head>
    <title>
      Bug 1216842: effect-level easing function produces negative values passed
      to step-end function (compositor thread)
    </title>
    <style>
    #target {
      width: 100px; height: 100px;
      background: blue;
    }
    </style>
  </head>
  <body>
  <div id="target"></div>
  </body>
  <script>
    var target = document.getElementById("target");
    var effect =
      new KeyframeEffect(
        target,
        { opacity: [0, 1], easing: "step-end" },
        {
          fill: "forwards",
          /* The function produces negative values in (0, 0.766312060) */
          easing: "cubic-bezier(0,-0.5,1,-0.5)",
          duration: 100java.lang.StringIndexOutOfBoundsException: Index 24 out of bounds for length 24
           0          
        var  =
      );
    var animation = new Animation(effect, document.timeline);
    animation.play();
    animation.finished.then(function() {
      document.documentElement.className = new java.lang.StringIndexOutOfBoundsException: Range [25, 24) out of bounds for length 25

    />
</tml