IntersectionObserver: use an idle callback to send notifications.

third_party/WebKit/LayoutTests/intersection-observer/observer-without-js-reference.html

Index: third_party/WebKit/LayoutTests/intersection-observer/observer-without-js-reference.html
diff --git a/third_party/WebKit/LayoutTests/intersection-observer/observer-without-js-reference.html b/third_party/WebKit/LayoutTests/intersection-observer/observer-without-js-reference.html
index 637a955f3c97d1c963356a5e20b30d590884e7db..6db0fa0ce40dfe617b5bd50fd6952024b4b3ef97 100644
--- a/third_party/WebKit/LayoutTests/intersection-observer/observer-without-js-reference.html
+++ b/third_party/WebKit/LayoutTests/intersection-observer/observer-without-js-reference.html
@@ -6,19 +6,19 @@
 <div style="width:100%; height:700px;"></div>
 
 <script>
-  jsTestIsAsync = true;
-  description("IntersectionObserver continues to produce notifications when it has no javascript references.");
-  var target = document.getElementById("target");
-  var entries = [];
-  new IntersectionObserver(function(changes) {
-      entries.push(...changes);
-  }).observe(target);
-  gc();
-  document.scrollingElement.scrollTop = 300;
-  requestAnimationFrame(function () {
-    setTimeout(function() {
-      shouldBeEqualToNumber("entries.length", 1);
-      finishJSTest();
-    });
-  });
+jsTestIsAsync = true;
+description("IntersectionObserver continues to produce notifications when it has no javascript references.");
+var target = document.getElementById("target");
+var entries = [];
+new IntersectionObserver(function(changes) {
+    entries.push(...changes);
+}).observe(target);
+gc();
+document.scrollingElement.scrollTop = 300;
+requestAnimationFrame(() => { requestAnimationFrame(() => {
+  setTimeout(() => {
+    shouldBeEqualToNumber("entries.length", 1);
+    finishJSTest();
+  }, 100);

[Sami, 2016/03/08 17:32:42]

Is there a chance this could add some flake?

[szager1, 2016/03/08 18:51:32]

In other tests, I added a call to observer.takeRecords() to ensure that the test
wasn't missing any pending notifications.  This test is meant to cover the case
where there are no remaining js references to the observer, so it can't use
takeRecords in this way.

However, the IO spec guarantees that notifications will be delivered within
100ms, so this tests conformance to that spec.

[Sami, 2016/03/09 18:29:55]

I see, that makes sense. Maybe also add corresponding comment here?

[szager1, 2016/03/09 20:45:25]

Done.

+}) });
 </script>