longtask-before-observer.window.js (646B)
1 // META: script=resources/utils.js 2 3 async_test(t => { 4 assert_implements(window.PerformanceLongTaskTiming, 'Longtasks are not supported.'); 5 // Create a long task before any observer. 6 const begin = window.performance.now(); 7 while (window.performance.now() < begin + 60); 8 // After a timeout, add an observer with buffered flag. 9 t.step_timeout(() => { 10 new PerformanceObserver(t.step_func_done(list => { 11 list.getEntries().forEach(entry => { 12 checkLongTaskEntry(entry); 13 }); 14 })).observe({type: 'longtask', buffered: true}); 15 }, 0); 16 }, 'PerformanceObserver with buffered flag can see previous longtask entries.');