Import Cobalt 21.master.0.253153
diff --git a/src/third_party/web_platform_tests/intersection-observer/timestamp.html b/src/third_party/web_platform_tests/intersection-observer/timestamp.html
new file mode 100644
index 0000000..3f573bc
--- /dev/null
+++ b/src/third_party/web_platform_tests/intersection-observer/timestamp.html
@@ -0,0 +1,100 @@
+<!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);
+}
+
+</style>
+<div id="leading-space" class="spacer"></div>
+<div id="trailing-space" class="spacer"></div>
+
+<script>
+// Pick this number to be comfortably greater than the length of two frames at 60Hz.
+var timeSkew = 40;
+
+var topWindowEntries = [];
+var iframeWindowEntries = [];
+var targetIframe;
+var topWindowTimeBeforeNotification;
+var iframeWindowTimeBeforeNotification;
+
+async_test(function(t) {
+ t.step_timeout(function() {
+ targetIframe = document.createElement("iframe");
+ assert_true(!!targetIframe, "iframe exists");
+ targetIframe.src = "resources/timestamp-subframe.html";
+ var trailingSpace = document.getElementById("trailing-space");
+ assert_true(!!trailingSpace, "trailing-space exists");
+ trailingSpace.parentNode.insertBefore(targetIframe, trailingSpace);
+ targetIframe.onload = function() {
+ var target = targetIframe.contentDocument.getElementById("target");
+ var iframeScroller = targetIframe.contentDocument.scrollingElement;
+
+ // Observer created here, callback created in iframe context. Timestamps should be
+ // from this window.
+ var observer = new IntersectionObserver(
+ targetIframe.contentDocument.createObserverCallback(topWindowEntries), {});
+ assert_true(!!observer, "Observer exists");
+ observer.observe(target);
+
+ // Callback created here, observer created in iframe. Timestamps should be
+ // from iframe window.
+ observer = targetIframe.contentDocument.createObserver(function(newEntries) {
+ iframeWindowEntries = iframeWindowEntries.concat(newEntries);
+ });
+ observer.observe(target);
+ runTestCycle(step1, "First rAF after iframe is loaded.");
+ t.done();
+ };
+ }, timeSkew);
+}, "Check that timestamps correspond to the to execution context that created the observer.");
+
+function step1() {
+ document.scrollingElement.scrollTop = 200;
+ targetIframe.contentDocument.scrollingElement.scrollTop = 250;
+ topWindowTimeBeforeNotification = performance.now();
+ iframeWindowTimeBeforeNotification = targetIframe.contentWindow.performance.now();
+ runTestCycle(step2, "Generate notifications.");
+ assert_equals(topWindowEntries.length, 1, "One notification to top window observer.");
+ assert_equals(iframeWindowEntries.length, 1, "One notification to iframe observer.");
+}
+
+function step2() {
+ document.scrollingElement.scrollTop = 0;
+ var topWindowTimeAfterNotification = performance.now();
+ var iframeWindowTimeAfterNotification = targetIframe.contentWindow.performance.now();
+
+ assert_approx_equals(
+ topWindowEntries[1].time - topWindowTimeBeforeNotification,
+ iframeWindowEntries[1].time - iframeWindowTimeBeforeNotification,
+ // Since all intersections are computed in a tight loop between 2 frames,
+ // an epsilon of 16ms (the length of one frame at 60Hz) turned out to be
+ // reliable, even at slow frame rates.
+ 16,
+ "Notification times are relative to the expected time origins");
+
+ assert_equals(topWindowEntries.length, 2, "Top window observer has two notifications.");
+ assert_between_inclusive(
+ topWindowEntries[1].time,
+ topWindowTimeBeforeNotification,
+ topWindowTimeAfterNotification,
+ "Notification to top window observer is within the expected range.");
+
+ assert_equals(iframeWindowEntries.length, 2, "Iframe observer has two notifications.");
+ assert_between_inclusive(
+ iframeWindowEntries[1].time,
+ iframeWindowTimeBeforeNotification,
+ iframeWindowTimeAfterNotification,
+ "Notification to iframe observer is within the expected range.");
+}
+</script>
