Import Cobalt 21.master.0.253153
diff --git a/src/third_party/web_platform_tests/intersection-observer/initial-observation-with-threshold.html b/src/third_party/web_platform_tests/intersection-observer/initial-observation-with-threshold.html
new file mode 100644
index 0000000..b9218b0
--- /dev/null
+++ b/src/third_party/web_platform_tests/intersection-observer/initial-observation-with-threshold.html
@@ -0,0 +1,61 @@
+<!DOCTYPE html>
+<meta name="viewport" content="width=device-width,initial-scale=1">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="./resources/intersection-observer-test-utils.js"></script>
+
+<style>
+pre, #log {
+ position: absolute;
+ top: 0;
+ left: 200px;
+}
+.spacer {
+ height: calc(100vh + 100px);
+}
+#root {
+ display: inline-block;
+ overflow-y: scroll;
+ height: 240px;
+ border: 3px solid black;
+}
+#target {
+ width: 100px;
+ height: 100px;
+ margin: 200px 0 0 0;
+ background-color: green;
+}
+</style>
+
+<div id="root">
+ <div id="target"></div>
+</div>
+
+<script>
+var entries = [];
+var root, target;
+
+runTestCycle(function() {
+ target = document.getElementById("target");
+ assert_true(!!target, "target exists");
+ root = document.getElementById("root");
+ assert_true(!!root, "root exists");
+ var observer = new IntersectionObserver(function(changes) {
+ entries = entries.concat(changes)
+ }, { root: root, threshold: [0.5] });
+ observer.observe(target);
+ entries = entries.concat(observer.takeRecords());
+ assert_equals(entries.length, 0, "No initial notifications.");
+ runTestCycle(step0, "First rAF");
+}, "First observation with a threshold.");
+
+function step0() {
+ root.scrollTop = 20;
+ runTestCycle(step1, "root.scrollTop = 20");
+ checkLastEntry(entries, 0, [ 11, 111, 211, 311, 11, 111, 211, 251, 11, 111, 11, 251, false]);
+}
+
+function step1() {
+ checkLastEntry(entries, 1, [ 11, 111, 191, 291, 11, 111, 191, 251, 11, 111, 11, 251, true]);
+}
+</script>
