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chromium/third_party/blink/web_tests/external/wpt/layout-instability/supported-layout-type.html 

<!DOCTYPE html>
<head>
<title>PerformanceObserver.supportedEntryTypes contains "layout-shift"</title>
</head>
<body>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script>
test(() => {
  assert_implements(window.LayoutShift, 'Layout Instability is not supported.');
  assert_implements(typeof PerformanceObserver.supportedEntryTypes !== "undefined",
      'supportedEntryTypes is not supported.');
  assert_greater_than(PerformanceObserver.supportedEntryTypes.indexOf("layout-shift"), -1,
    "There should be an entry 'layout-shift' in PerformanceObserver.supportedEntryTypes");
}, "supportedEntryTypes contains 'layoutShift'.");
</script>
</body>
</html>