IntersectionObserver: second cut.

third_party/WebKit/LayoutTests/intersection-observer/helper-functions.js

+// Some of the js-test.js boilerplate will add stuff to the top of the document early
+// enough to screw with frame offsets that are measured by the test.  Delay all that
+// jazz until the actual test code is finished.
+setPrintTestResultsLazily();
+var delayDescription = description;
+var descriptionString = "";
+var delayIsSuccessfullyParsed = isSuccessfullyParsed;
+var isSuccessfullyParsed = function() {}
+var description = function(msg) { descriptionString = msg }
+
+if (window.testRunner)
+  testRunner.waitUntilDone();
+
+function rectToString(rect) {
+  return "[" + rect.left + ", " + rect.right + ", " + rect.top + ", " + rect.bottom + "]";
+}
+
+function entryToString(entry) {
+  var ratio = ((entry.intersectionRect.width * entry.intersectionRect.height) /
+               (entry.boundingClientRect.width * entry.boundingClientRect.height));
+  return (
+      "boundingClientRect=" + rectToString(entry.boundingClientRect) + "\n" +
+      "intersectionRect=" + rectToString(entry.intersectionRect) + "\n" +
+      "visibleRatio=" + ratio + "\n" +
+      "rootBounds=" + rectToString(entry.rootBounds) + "\n" +
+      "target=" + entry.target + "\n" +
+      "time=" + entry.time);
+}
+
+function finishTest() {
+  if (descriptionString)
+    delayDescription(descriptionString);
+  delayIsSuccessfullyParsed();
+  finishJSTest();
+  if (window.testRunner)
+    testRunner.notifyDone();
+}