chromium/third_party/blink/web_tests/http/tests/inspector-protocol/resources/rendering-exercise.css

p {
    animation-duration: 3s;
    animation-name: slidein;
  }

  @keyframes slidein {
    from {
      margin-left: 100%;
      width: 300%;
    }

    to {
      margin-left: 0%;
      width: 100%;
    }
  }
  img {
    display: block;
    margin: 500px;
  }