1async_test(t => { 2 performance.mark('foo'); 3 // Use a timeout to ensure the remainder of the test runs after the entry is created. 4 t.step_timeout(() => { 5 // Observer with buffered flag set to false should not see entry. 6 new PerformanceObserver(() => { 7 assert_unreached('Should not have observed any entry!'); 8 }).observe({type: 'mark', buffered: false}); 9 // Use a timeout to give time to the observer. 10 t.step_timeout(t.step_func_done(() => {}), 100); 11 }, 0); 12}, 'PerformanceObserver without buffered flag set to false cannot see past entries.'); 13