yle.remove();
  }
  anim = 'anim' + nextAnim++;
  style = document.createElement('style');
  style.textContent = '\
  target {\
    -webkit-animation: ' + anim + ' 1s linear infinite;\
  }\n\
  @-webkit-keyframes ' + anim + ' {\
    0% { opacity: 0; }\
    100% { opacity: 1; }\
  }';
  container.appendChild(style);
}

updateStyle();
setInterval(updateStyle, duration);

PerfTestHelper.signalReady();
</script>
