Tools/TestWebKitAPI/Resources/simple-model-page.html

<script>
    internals.disableModelLoadDelaysForTesting()
</script>
<model>
    <source src='cube.usdz'>
</model>
<script>
    document.querySelector('model').addEventListener('load', event => window.webkit.messageHandlers.modelLoading.postMessage('LOADED'));
    document.querySelector('model').ready.then((result) => window.webkit.messageHandlers.modelLoading.postMessage('READY'));
</script>