chromium/third_party/blink/web_tests/external/wpt/css/filter-effects/css-backdrop-filters-animation-blur.html

<!DOCTYPE html>
<title>CSS Backdrop Filters Animation: Blur</title>
<link rel="author" href="mailto:[email protected]">
<link rel="help" href="https://drafts.fxtf.org/filter-effects-2/#BackdropFilterProperty">
<link rel="match" href="css-backdrop-filters-animation-blur-ref.html">
<style>
    @keyframes animate {
        0% {
            backdrop-filter: blur(20px);
        }
        100% {
            backdrop-filter: none;
        }
    }

    .square {
        position: absolute;
        width: 100px;
        height: 100px;
        top: 100px;
        left: 100px;
        background: blue;
    }
    .filt {
        position: absolute;
        width: 200px;
        height: 200px;
        top: 50px;
        left: 50px;
        animation-name: animate;
        animation-play-state: paused;
        animation-delay: -2s;
        animation-duration: 4s;
        animation-timing-function: linear;
    }
    .greenbox {
        position: absolute;
        width: 50px;
        height: 50px;
        top: 75px;
        left: 75px;
        background: green;
    }
</style>
<p>You should see a blurred rectangle with a green box.</p>
<div class="square"></div>
<div class="filt">
    <div class="greenbox"></div>
</div>