1 files changed, 15 insertions, 0 deletions
diff --git a/testing/web-platform/tests/performance-timeline/buffered-flag-observer.any.js b/testing/web-platform/tests/performance-timeline/buffered-flag-observer.any.js
new file mode 100644
index 0000000000..31dc39c128
--- /dev/null
+++ b/testing/web-platform/tests/performance-timeline/buffered-flag-observer.any.js
@@ -0,0 +1,15 @@
+async_test( t=> {
+  for (let i = 0; i < 50; i++)
+    performance.mark('foo' + i);
+  let marksCreated = 50;
+  let marksReceived = 0;
+  new PerformanceObserver(list => {
+    marksReceived += list.getEntries().length;
+    if (marksCreated < 100) {
+      performance.mark('bar' + marksCreated);
+      marksCreated++;
+    }
+    if (marksReceived == 100)
+      t.done();
+  }).observe({type: 'mark', buffered: true});
+}, 'PerformanceObserver with buffered flag should see past and future entries.');