Morph the APIs for Node, ParentNode, and Element closer to the specs

sky/tests/dom/document-child-mutations.sky

 <sky>
 <import src="../resources/dom-utils.sky" as="DomUtils" />
 <script>
 import "../resources/third_party/unittest/unittest.dart";
 import "../resources/unit.dart";
 
 import "dart:sky";
 
 void main() {
   initUnit();
 
   var doc;
 
   var childElementCount = DomUtils.childElementCount;
   var childNodeCount = DomUtils.childNodeCount;
 
   setUp(() {
     doc = new Document();
   });
 
   test("should allow replacing the document element", () {
     var oldChild = doc.appendChild(doc.createElement("div"));
     expect(childElementCount(doc), equals(1));
     var newChild = doc.createElement("div");
-    doc.replaceChild(newChild, oldChild);
+    oldChild.replaceWith([newChild]);
     expect(childElementCount(doc), equals(1));
     expect(newChild.parentNode, equals(doc));
     expect(oldChild.parentNode, isNull);
   });
 
   test("should allow replacing a text child with an element", () {
     var oldChild = doc.appendChild(new Text("text here"));
     expect(childElementCount(doc), equals(0));
     expect(childNodeCount(doc), equals(1));
     var newChild = doc.createElement("div");
-    doc.replaceChild(newChild, oldChild);
+    oldChild.replaceWith([newChild]);
     expect(childElementCount(doc), equals(1));
     expect(childNodeCount(doc), equals(1));
     expect(newChild.parentNode, equals(doc));
     expect(oldChild.parentNode, isNull);
   });
 
   test("should allow replacing the document element with text", () {
     var oldChild = doc.appendChild(doc.createElement("div"));
     expect(childElementCount(doc), equals(1));
     var newChild = new Text(" text ");
-    doc.replaceChild(newChild, oldChild);
+    oldChild.replaceWith([newChild]);
     expect(childElementCount(doc), equals(0));
     expect(childNodeCount(doc), equals(1));
     expect(newChild.parentNode, equals(doc));
     expect(oldChild.parentNode, isNull);
   });
 
   test("should allow inserting text with a fragment", () {
     var fragment = doc.createDocumentFragment();
     fragment.appendChild(new Text(" text "));
     fragment.appendChild(new Text(" text "));
     expect(childNodeCount(doc), equals(0));
     doc.appendChild(fragment);
     expect(childElementCount(doc), equals(0));
     expect(childNodeCount(doc), equals(2));
   });
 
   test("should allow replacing the document element with a fragment", () {
     var oldChild = doc.appendChild(doc.createElement("div"));
     expect(childElementCount(doc), equals(1));
     var fragment = doc.createDocumentFragment();
     fragment.appendChild(new Text(" text "));
     var newChild = fragment.appendChild(doc.createElement("div"));
     fragment.appendChild(new Text(" "));
-    doc.replaceChild(fragment, oldChild);
+    oldChild.replaceWith([fragment]);
     expect(childElementCount(doc), equals(1));
     expect(childNodeCount(doc), equals(3));
     expect(newChild.parentNode, equals(doc));
     expect(oldChild.parentNode, isNull);
   });
 
   test("should throw when inserting multiple elements", () {
     doc.appendChild(doc.createElement("div"));
     var oldChild = doc.appendChild(new Text(" text "));
     expect(childElementCount(doc), equals(1));
@@ skipping 17 matching lines @@
     // expect(() {
     //   doc.replaceChild(fragment, 0);
     // }, throws);
     // expect(() {
     //   doc.insertBefore(fragment, oldChild);
     // }, throws);
   });
 }
 </script>
 </sky>