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Test Info: Warnings

<meta charset=utf-8>
<title>Layout Instability: toJSON</title>
#myDiv { position: relative; width: 300px; height: 100px; background: blue; }
<div id='myDiv'></div>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="resources/util.js"></script>
promise_test(async t => {
assert_implements(window.LayoutShift, 'Layout Instability is not supported.');
// Wait for the initial render to complete.
await waitForAnimationFrames(2);
return new Promise(resolve => {
const observer = new PerformanceObserver(
t.step_func(entryList => {
const entry = entryList.getEntries()[0];
assert_equals(typeof(entry.toJSON), 'function');
const json = entry.toJSON();
assert_equals(typeof(json), 'object');
const keys = [
// PerformanceEntry
// LayoutShift
for (const key of keys) {
assert_equals(json[key], entry[key],
`LayoutShift ${key} entry does not match its toJSON value`);
observer.observe({type: 'layout-shift'});
document.getElementById('myDiv').style = "top: 60px";
}, 'Test toJSON() in LayoutShift.');