1 files changed, 32 insertions, 0 deletions
diff --git a/testing/web-platform/tests/performance-timeline/multiple-buffered-flag-observers.any.js b/testing/web-platform/tests/performance-timeline/multiple-buffered-flag-observers.any.js
new file mode 100644
index 0000000000..5dd44fb18f
--- /dev/null
+++ b/testing/web-platform/tests/performance-timeline/multiple-buffered-flag-observers.any.js
@@ -0,0 +1,32 @@
+promise_test(() => {
+  // The first promise waits for one buffered flag observer to receive 3 entries.
+  const promise1 = new Promise(resolve1 => {
+    let numObserved1 = 0;
+    new PerformanceObserver((entryList, obs) => {
+      // This buffered flag observer is constructed after a regular observer detects a mark.
+      new PerformanceObserver(list => {
+        numObserved1 += list.getEntries().length;
+        if (numObserved1 == 3)
+          resolve1();
+      }).observe({type: 'mark', buffered: true});
+      obs.disconnect();
+    }).observe({entryTypes: ['mark']});
+    performance.mark('foo');
+  });
+  // The second promise waits for another buffered flag observer to receive 3 entries.
+  const promise2 = new Promise(resolve2 => {
+    step_timeout(() => {
+      let numObserved2 = 0;
+      // This buffered flag observer is constructed after a delay of 100ms.
+      new PerformanceObserver(list => {
+        numObserved2 += list.getEntries().length;
+        if (numObserved2 == 3)
+          resolve2();
+      }).observe({type: 'mark', buffered: true});
+    }, 100);
+    performance.mark('bar');
+  });
+  performance.mark('meow');
+  // Pass if and only if both buffered observers received all 3 mark entries.
+  return Promise.all([promise1, promise2]);
+}, 'Multiple PerformanceObservers with buffered flag see all entries');