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) +
+      "\nintersectionRect=" + rectToString(entry.intersectionRect) +
+      "\nvisibleRatio=" + ratio +
+      "\nrootBounds=" + rectToString(entry.rootBounds) +
+      "\ntarget=" + entry.target +
+      "\ntime=" + entry.time);
+}
+
+function finishTest() {
+  if (descriptionString)
+    delayDescription(descriptionString);
+  delayIsSuccessfullyParsed();
+  finishJSTest();
+  if (window.testRunner)
+    testRunner.notifyDone();
+}
+
+function rectToString(rect) {
+  return "[" + rect.left + ", " + rect.right + ", " + rect.top + ", " + rect.bottom + "]";
+}
+
+function checkRect(expected, actual) {
+  shouldBeEqualToNumber(actual + ".left", expected[0]);
+  shouldBeEqualToNumber(actual + ".right", expected[1]);
+  shouldBeEqualToNumber(actual + ".top", expected[2]);
+  shouldBeEqualToNumber(actual + ".bottom", expected[3]);
+}
+
+function checkEntry(expected, actual) {
+  checkRect(expected['boundingClientRect'], actual + ".boundingClientRect");
+  checkRect(expected['intersectionRect'], actual + ".intersectionRect");
+  checkRect(expected['rootBounds'], actual + ".rootBounds");
+  var actual_target = eval(actual + ".target");
+  if (isResultCorrect(actual_target, expected['target']))
+    testPassed(actual + ".target is " + expected);
+  else
+    testFailed(actual + ".target should be " + stringify(expected) + ". Was " + actual_target + ".");
+}
+
+function checkResults(expected, actual, startFrom = 0) {
+  shouldBeEqualToNumber(actual + ".length", expected.length);
+  var max = Math.min(eval(actual + ".length"), expected.length);
+  for (var i = startFrom; i < max; i++)
+    checkEntry(expected[i], actual + "[" + i + "]");
+}