<!DOCTYPE HTML> <meta charset=utf-8> <title>LongTask Timing: long task in nested child iframe</title> <body> <script src="/resources/testharness.js"></script> <script src="/resources/testharnessreport.js"></script> <script src="resources/utils.js"></script> <h1>Long Tasks with detached iframe</h1> <div id="log"></div> <script> promise_test(async t => { assert_implements(window.PerformanceLongTaskTiming, 'Longtasks are not supported.'); const iframe = document.createElement("iframe"); document.body.appendChild(iframe); t.add_cleanup(() => iframe.remove()); t.step_timeout(() => { busyWait(); iframe.remove(); }); }, 'Performance longtask entries dont crash when a frame is detached.'); </script> </body>