1 files changed, 24 insertions, 0 deletions
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/buffered-flag.window.js b/testing/web-platform/tests/paint-timing/fcp-only/buffered-flag.window.js
new file mode 100644
index 0000000000..5910b6881f
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/buffered-flag.window.js
@@ -0,0 +1,24 @@
+setup({"hide_test_state": true});
+async_test(t => {
+  assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+  // First observer creates a second one in the callback to ensure the entry has been dispatched
+  // by the time the second observer begins observing.
+  new PerformanceObserver(entries => {
+    const entry_seen = entries.getEntriesByName('first-contentful-paint').length > 0;
+    // Abort if we have not yet received the entry.
+    if (!entry_seen)
+      return;
+
+    // Second observer requires 'buffered: true' to see the entry.
+    new PerformanceObserver(t.step_func_done(list => {
+        const fcp = list.getEntriesByName('first-contentful-paint');
+        assert_equals(fcp.length, 1, 'Should have an fcp entry');
+        const entry = fcp[0];
+        assert_equals(entry.entryType, 'paint');
+      })).observe({'type': 'paint', buffered: true});
+  }).observe({'entryTypes': ['paint']});
+  // Trigger the first contentful paint entry.
+  const img = document.createElement("img");
+  img.src = "../resources/circles.png";
+  document.body.appendChild(img);
+}, "PerformanceObserver with buffered flag sees previous FCP entry.");