Convert IntersectionObserver tests to use testRunner.runIdleTasks.

third_party/WebKit/LayoutTests/intersection-observer/iframe-no-root.html

Index: third_party/WebKit/LayoutTests/intersection-observer/iframe-no-root.html
diff --git a/third_party/WebKit/LayoutTests/intersection-observer/iframe-no-root.html b/third_party/WebKit/LayoutTests/intersection-observer/iframe-no-root.html
index 134b6455d55259481cf48160abac7b590c00b899..d4c8b4e42666d82f460c8670152081527121dcac 100644
--- a/third_party/WebKit/LayoutTests/intersection-observer/iframe-no-root.html
+++ b/third_party/WebKit/LayoutTests/intersection-observer/iframe-no-root.html
@@ -19,26 +19,22 @@ targetIframe.onload = function() {
   observer.observe(target);
   entries = entries.concat(observer.takeRecords());
   shouldBeEqualToNumber("entries.length", 0);
-  // See README for explanation of double RAF.
-  requestAnimationFrame(() => { requestAnimationFrame(step0) });
+  waitForNotification(step0);
 }
 
 function step0() {
-  entries = entries.concat(observer.takeRecords());
   shouldBeEqualToNumber("entries.length", 0);
   document.scrollingElement.scrollTop = 200;
-  requestAnimationFrame(step1);
+  waitForNotification(step1);
 }
 
 function step1() {
-  entries = entries.concat(observer.takeRecords());
   shouldBeEqualToNumber("entries.length", 0);
   iframeScroller.scrollTop = 250;
-  requestAnimationFrame(step2);
+  waitForNotification(step2);
 }
 
 function step2() {
-  entries = entries.concat(observer.takeRecords());
   shouldBeEqualToNumber("entries.length", 1);
   if (entries.length > 0) {
     shouldBeEqualToNumber("entries[0].boundingClientRect.left", 8);
@@ -56,11 +52,10 @@ function step2() {
     shouldEvaluateToSameObject("entries[0].target", target);
   }
   document.scrollingElement.scrollTop = 100;
-  requestAnimationFrame(step3);
+  waitForNotification(step3);
 }
 
 function step3() {
-  entries = entries.concat(observer.takeRecords());
   shouldBeEqualToNumber("entries.length", 2);
   if (entries.length > 1) {
     shouldBeEqualToNumber("entries[1].boundingClientRect.left", 8);