IntersectionObserver: use an idle callback to send notifications.

third_party/WebKit/LayoutTests/http/tests/intersection-observer/resources/cross-origin-subframe.html

Index: third_party/WebKit/LayoutTests/http/tests/intersection-observer/resources/cross-origin-subframe.html
diff --git a/third_party/WebKit/LayoutTests/http/tests/intersection-observer/resources/cross-origin-subframe.html b/third_party/WebKit/LayoutTests/http/tests/intersection-observer/resources/cross-origin-subframe.html
index d2a40dd8987e6bfdd33ccae4f74d864484593864..eda791fae670431f70a6ca3c0678ef80719c4337 100644
--- a/third_party/WebKit/LayoutTests/http/tests/intersection-observer/resources/cross-origin-subframe.html
+++ b/third_party/WebKit/LayoutTests/http/tests/intersection-observer/resources/cross-origin-subframe.html
@@ -14,60 +14,54 @@ var nextStep;
 // Instead of RAF-ing, we just post an empty message to the parent window, which will
 // RAF when it is received, and then send us a message to cause the next step to run.
 
-function observer_callback(changes) {
-  for (var i in changes)
-    entries.push(changes[i]);
-}
-
 // Use a rootMargin here, and verify it does NOT get applied for the cross-origin case.
-var observer = new IntersectionObserver(observer_callback, {rootMargin: "7px"});
+var observer = new IntersectionObserver(
+    changes => { entries = entries.concat(changes) },
+    { rootMargin: "7px" }
+);
 observer.observe(target);
 
 function step0() {
-  setTimeout(function() {
-    nextStep = step1;
-    port.postMessage({actual: entries.map(entryToJson), expected: []}, "*");
-    entries = [];
-    port.postMessage({scrollTo: 200}, "*");
-  });
+  entries = entries.concat(observer.takeRecords());
+  nextStep = step1;
+  port.postMessage({actual: entries.map(entryToJson), expected: []}, "*");
+  entries = [];
+  port.postMessage({scrollTo: 200}, "*");
 }
 
 function step1() {
-  setTimeout(function() {
-    port.postMessage({actual: entries.map(entryToJson), expected: []}, "*");
-    entries = [];
-    scroller.scrollTop = 250;
-    nextStep = step2;
-    port.postMessage({}, "*");
-  });
+  entries = entries.concat(observer.takeRecords());
+  port.postMessage({actual: entries.map(entryToJson), expected: []}, "*");
+  entries = [];
+  scroller.scrollTop = 250;
+  nextStep = step2;
+  port.postMessage({}, "*");
 }
 
 function step2() {
-  setTimeout(function() {
-    var expected = [{
-      boundingClientRect: coordinatesToClientRectJson(-42, 108, 58, 8),
-      intersectionRect: coordinatesToClientRectJson(0, 108, 58, 8),
-      rootBounds: "null",
-      target: target.id
-    }];
-    port.postMessage({actual: entries.map(entryToJson), expected: expected}, "*");
-    entries = [];
-    nextStep = step3;
-    port.postMessage({scrollTo: 100}, "*");
-  });
+  entries = entries.concat(observer.takeRecords());
+  var expected = [{
+    boundingClientRect: coordinatesToClientRectJson(-42, 108, 58, 8),
+    intersectionRect: coordinatesToClientRectJson(0, 108, 58, 8),
+    rootBounds: "null",
+    target: target.id
+  }];
+  port.postMessage({actual: entries.map(entryToJson), expected: expected}, "*");
+  entries = [];
+  nextStep = step3;
+  port.postMessage({scrollTo: 100}, "*");
 }
 
 function step3() {
-  setTimeout(function() {
-    var expected = [{
-      boundingClientRect: coordinatesToClientRectJson(-42, 108, 58, 8),
-      intersectionRect: coordinatesToClientRectJson(0, 0, 0, 0),
-      rootBounds: "null",
-      target: target.id
-    }];
-    port.postMessage({actual: entries.map(entryToJson), expected: expected}, "*");
-    port.postMessage({DONE: 1}, "*");
-  });
+  entries = entries.concat(observer.takeRecords());
+  var expected = [{
+    boundingClientRect: coordinatesToClientRectJson(-42, 108, 58, 8),
+    intersectionRect: coordinatesToClientRectJson(0, 0, 0, 0),
+    rootBounds: "null",
+    target: target.id
+  }];
+  port.postMessage({actual: entries.map(entryToJson), expected: expected}, "*");
+  port.postMessage({DONE: 1}, "*");
 }
 
 function handleMessage(event)