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<!DOCType html>
<html>
<style>
body {
margin: 0;
}
</style>
<body>
<script>
const observer = new PerformanceObserver(entryList => {
top.postMessage({
'length' : entryList.getEntries().length,
'entryType' : entryList.getEntries()[0].entryType,
'rect' : entryList.getEntries()[0].intersectionRect,
'naturalWidth' : entryList.getEntries()[0].naturalWidth,
'naturalHeight' : entryList.getEntries()[0].naturalHeight,
'id': entryList.getEntries()[0].id,
// Elements cannot be cloned, so just send the element ID.
'elementId' : entryList.getEntries()[0].element.id,
}, '*');
});
observer.observe({entryTypes: ['element']});
</script>
<img src=square100.png id=iframe_img_id elementtiming=my_image/>
</body>
</html>