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+<!DOCTYPE HTML>
+<meta charset=utf-8>
+<title>PerformanceObservers: PerformanceObserverInit.buffered</title>
+<meta name="timeout" content="long">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="performanceobservers.js"></script>
+<h1>PerformanceObservers: PerformanceObserverInit.buffered</h1>
+<p>
+PerformanceObserverInit.buffered should retrieve previously buffered entries
+</p>
+<div id="log"></div>
+<script>
+  async_test(function (t) {
+    function initTest() {
+      new PerformanceObserver(function (entryList, observer) {
+        entryList.getEntries().forEach(function(entry) {
+          if (shouldExclude(entry)) {
+            return;
+          }
+
+          observedEntries.push(entry);
+          if (observedEntries.length === entryTypes.length) {
+            observer.disconnect();
+            runTest();
+          }
+        });
+      }).observe({entryTypes});
+
+      // creates a `resource` entry
+      var img = document.createElement("img");
+      img.src = "./resources/square.png";
+      document.body.appendChild(img);
+
+      performance.mark("markName"); // creates a `mark` entry
+      performance.measure("measureName"); // creates a `measure` entry
+    }
+    function shouldExclude(entry) {
+      // exclude all `resource` entries that aren't for "square.png"
+      return entry.entryType === "resource" &&
+             entry.name.indexOf("square.png") === -1;
+    }
+    function runTest() {
+      // this PerformanceObserver is a nop because we've already been notified about all of our `entryTypes`
+      var po_nop = new PerformanceObserver(function (entryList, observer) {
+        if (entryList.getEntries().find(function(entry) {
+          return !shouldExclude(entry);
+        })) {
+          assert_unreached("this PerformanceObserver callback should never be called");
+        }
+      });
+      po_nop.observe({
+        entryTypes,
+      });
+
+      // this PerformanceObserver should be notified about the previously
+      // buffered mark entry only
+      const bufferedEntries = [];
+      new PerformanceObserver(function (entryList, observer) {
+        entryList.getEntries().forEach(function(entry) {
+          if (shouldExclude(entry)) {
+            return;
+          }
+
+          bufferedEntries.push(entry);
+          if (bufferedEntries.length === 1) {
+            observer.disconnect();
+            po_nop.disconnect();
+            for (i = 0; i < bufferedEntries.length; i++) {
+              assert_equals(bufferedEntries[i].entryType, "mark")
+            }
+            t.done();
+          }
+        });
+      }).observe({
+        type: "mark",
+        buffered: true
+      });
+    }
+
+    const entryTypes = ["navigation", "resource", "mark", "measure"];
+    const observedEntries = [];
+    initTest();
+  }, "PerformanceObserverInit.buffered should retrieve previously buffered entries");
+
+</script>