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<!DOCTYPE html>
<html>
<body>
<title>Layout Instability: subframe layout shift score</title>
<link rel="help" href="https://wicg.github.io/layout-instability/" />
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
#i {
border: 0;
position: absolute;
left: 0;
top: 0;
background-color: pink;
}
</style>
<iframe id="i" width="400" height="300" src="sub-frame.html"></iframe>
<script>
const loadPromise = new Promise(resolve => {
window.addEventListener("load", () => {
resolve(true);
});
});
let iframe = document.getElementById('i');
const load_promise = new Promise(resolve => {
iframe.addEventListener('load', function() {
resolve(true);
});
});
checkMainFrameLoad = async () => {
await loadPromise;
return true;
};
checkIFrameLoad = async () => {
// Wait for the iframe finishing loading
await load_promise;
return true;
};
promise_test(async t => {
checkMainFrameLoad();
// Wait for the iframe finishing loading
checkIFrameLoad();
// Wait for the message sent from the iframe after it receives all the layout
// shifts.
await new Promise(resolve => {
window.addEventListener("message", (event) => {
if (event.data.type == "layout shift score") {
t.step(() => {
assert_equals(event.data.score, event.data.expectedScore);
});
resolve();
}
}, false);
});
}, "");
</script>
</body>
</html>
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