diff --git a/testing/web-platform/meta/MANIFEST.json b/testing/web-platform/meta/MANIFEST.json
index a2d0b555bd2f6..3a68e175ea621 100644
--- a/testing/web-platform/meta/MANIFEST.json
+++ b/testing/web-platform/meta/MANIFEST.json
@@ -287098,6 +287098,11 @@
      {}
     ]
    ],
+   "html/user-activation/resources/child-three.html": [
+    [
+     {}
+    ]
+   ],
    "html/user-activation/resources/child-two.html": [
     [
      {}
@@ -360760,6 +360765,20 @@
      }
     ]
    ],
+   "html/user-activation/message-event-activation-api-iframe-cross-origin.sub.tentative.html": [
+    [
+     "/html/user-activation/message-event-activation-api-iframe-cross-origin.sub.tentative.html",
+     {
+      "testdriver": true
+     }
+    ]
+   ],
+   "html/user-activation/message-event-init.tentative.html": [
+    [
+     "/html/user-activation/message-event-init.tentative.html",
+     {}
+    ]
+   ],
    "html/webappapis/animation-frames/callback-exception.html": [
     [
      "/html/webappapis/animation-frames/callback-exception.html",
@@ -599905,10 +599924,22 @@
    "96d17e27c892ec988ba5acdfb60fd1f9edd16571",
    "manual"
   ],
+  "html/user-activation/message-event-activation-api-iframe-cross-origin.sub.tentative.html": [
+   "63a1da05d0005c33bec1af8a58e7f011d5b09d4c",
+   "testharness"
+  ],
+  "html/user-activation/message-event-init.tentative.html": [
+   "8e2b1d07014e8bd754d943e11672fff0719bbb74",
+   "testharness"
+  ],
   "html/user-activation/resources/child-one.html": [
    "9c99729b6a98022f7449bae62a7bea616308c0c7",
    "support"
   ],
+  "html/user-activation/resources/child-three.html": [
+   "5a74cf5360c6a14d2ad5eebb31d74db6980ebccf",
+   "support"
+  ],
   "html/user-activation/resources/child-two.html": [
    "7d48789878a902e8a773548e2012665d279fb4ea",
    "support"
diff --git a/testing/web-platform/tests/html/user-activation/message-event-activation-api-iframe-cross-origin.sub.tentative.html b/testing/web-platform/tests/html/user-activation/message-event-activation-api-iframe-cross-origin.sub.tentative.html
new file mode 100644
index 0000000000000..63a1da05d0005
--- /dev/null
+++ b/testing/web-platform/tests/html/user-activation/message-event-activation-api-iframe-cross-origin.sub.tentative.html
@@ -0,0 +1,55 @@
+<!DOCTYPE html>
+<!--
+   Tentative due to:
+    https://github.com/whatwg/html/issues/3739
+
+-->
+<html>
+<head>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/testdriver.js"></script>
+<script src="/resources/testdriver-vendor.js"></script>
+</head>
+<body>
+  <h1>Clicking in iframe has activation state in child via MessageEvent</h1>
+  <ol id="instructions">
+    <li>Click inside the red area.
+  </ol>
+  <iframe id="child" width="200" height="200"></iframe>
+  <script>
+    async_test(function(t) {
+      var child = document.getElementById("child");
+      assert_false(navigator.userActivation.isActive);
+      assert_false(navigator.userActivation.hasBeenActive);
+      window.addEventListener("message", t.step_func(event => {
+        if (event.data == 'child-three-loaded') {
+          // values have false after load
+          assert_true(event.userActivation != null);
+          assert_false(event.userActivation.isActive);
+          assert_false(event.userActivation.hasBeenActive);
+          test_driver.click(child);
+        } else if (event.data == 'child-three-clicked') {
+          // values have activation state on click
+          assert_true(navigator.userActivation.hasBeenActive);
+          assert_true(event.userActivation != null);
+          assert_true(event.userActivation.isActive);
+          assert_true(event.userActivation.hasBeenActive);
+          child.contentWindow.postMessage('report', "*");
+        } else if (event.data == 'child-three-report') {
+          assert_false(navigator.userActivation.isActive);
+          assert_true(navigator.userActivation.hasBeenActive);
+          assert_true(event.userActivation != null);
+          assert_false(event.userActivation.isActive);
+          assert_true(event.userActivation.hasBeenActive);
+          child.contentWindow.postMessage('report-no-activation', "*");
+        } else if (event.data == 'child-three-report-no-activation') {
+          assert_true(event.userActivation === null);
+          t.done();
+        }
+      }));
+      child.src = "http://{{domains[www]}}:{{ports[http][0]}}/html/user-activation/resources/child-three.html";
+    }, "Message propagates values on post");
+  </script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/html/user-activation/message-event-init.tentative.html b/testing/web-platform/tests/html/user-activation/message-event-init.tentative.html
new file mode 100644
index 0000000000000..8e2b1d07014e8
--- /dev/null
+++ b/testing/web-platform/tests/html/user-activation/message-event-init.tentative.html
@@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<title>MessageEvent constructor</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+test(function() {
+  var ev = new MessageEvent("test", { userActivation: navigator.userActivation })
+  assert_equals(ev.userActivation, navigator.userActivation, "userActivation attribute")
+}, "MessageEventInit user activation set")
+test(function() {
+  var ev = new MessageEvent("test")
+  assert_equals(ev.userActivation, null, "userActivation attribute")
+}, "MessageEventInit user activation not set")
+
+</script>
diff --git a/testing/web-platform/tests/html/user-activation/resources/child-three.html b/testing/web-platform/tests/html/user-activation/resources/child-three.html
new file mode 100644
index 0000000000000..5a74cf5360c6a
--- /dev/null
+++ b/testing/web-platform/tests/html/user-activation/resources/child-three.html
@@ -0,0 +1,19 @@
+<!DOCTYPE html>
+<body style="background: red;">
+  <script>
+    window.parent.postMessage("child-three-loaded", {targetOrigin: "*", includeUserActivation: true});
+    window.addEventListener("click", event => {
+      window.parent.postMessage("child-three-clicked", {targetOrigin: "*", includeUserActivation: true});
+      var win = window.open('404.html');
+      win.close();
+  });
+
+  window.addEventListener("message", event => {
+    if (event.data == "report")
+      window.parent.postMessage("child-three-report", {targetOrigin: "*", includeUserActivation: true});
+    if (event.data == "report-no-activation")
+      window.parent.postMessage("child-three-report-no-activation", {targetOrigin: "*", includeUserActivation: false});
+  });
+
+</script>
+</body>
