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

sky/tests/dom/replaceChild.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 childElementCount = DomUtils.childElementCount;
   var childNodeCount = DomUtils.childNodeCount;
 
-  test("should throw with invalid arguments", () {
-    var parent = document.createElement("div");
-    expect(() {
-      parent.replaceChild();
-    }, throws);
-    // expect(() {
-    //   parent.replaceChild(null, null);
-    // }, throws);
-    expect(() {
-      parent.replaceChild({tagName: "div"});
-    }, throws);
-    // expect(() {
-    //   parent.replaceChild(null, document.createElement("div"));
-    // }, throws);
-    expect(() {
-      parent.replaceChild(document.createElement("div"), {tagName: "div"});
-    }, throws);
-  });
-
   test("should replace elements", () {
     var parent = document.createElement("div");
     var oldChild = parent.appendChild(document.createElement("div"));
     var newChild = document.createElement("div");
-    parent.replaceChild(newChild, oldChild);
+    oldChild.replaceWith([newChild]);
     expect(oldChild.parentNode, isNull);
     expect(newChild.parentNode, equals(parent));
   });
 
   test("should replace text", () {
     var parent = document.createElement("div");
     var oldChild = parent.appendChild(new Text(" it's a text "));
     var newChild = document.createElement("div");
-    parent.replaceChild(newChild, oldChild);
+    oldChild.replaceWith([newChild]);
     expect(oldChild.parentNode, isNull);
     expect(newChild.parentNode, equals(parent));
   });
 
   test("should replace children with a fragment", () {
     var fragment = document.createDocumentFragment();
     var child1 = fragment.appendChild(document.createElement("div"));
     var child2 = fragment.appendChild(new Text(" text "));
     var child3 = fragment.appendChild(new Text(" "));
     var child4 = fragment.appendChild(document.createElement("div"));
     var parent = document.createElement("div");
     var oldChild = parent.appendChild(document.createElement("div"));
     var lastChild = parent.appendChild(document.createElement("div"));
-    parent.replaceChild(fragment, oldChild);
+    oldChild.replaceWith([fragment]);
     expect(child1.parentNode, equals(parent));
     expect(child2.parentNode, equals(parent));
     expect(child3.parentNode, equals(parent));
     expect(child4.parentNode, equals(parent));
     expect(oldChild.parentNode, isNull);
     expect(childNodeCount(parent), equals(5));
     expect(childElementCount(parent), equals(3));
     expect(parent.lastChild, equals(lastChild));
   });
 
@@ skipping 14 matching lines @@
 
   // test("should throw when appending to a text", () {
   //   var parent = new Text();
   //   expect(() {
   //     parent.replaceChild(document.createElement("div"), null);
   //   }, throws);
   // });
 }
 </script>
 </sky>