Implement DOM: prepend, append, before, after & replaceWith

LayoutTests/fast/dom/script-tests/childnode-before.js

Index: LayoutTests/fast/dom/script-tests/childnode-before.js
diff --git a/LayoutTests/fast/dom/script-tests/childnode-before.js b/LayoutTests/fast/dom/script-tests/childnode-before.js
new file mode 100644
index 0000000000000000000000000000000000000000..cbd52add1f940870f0f8fc564c57a29cab60b2b0
--- /dev/null
+++ b/LayoutTests/fast/dom/script-tests/childnode-before.js
@@ -0,0 +1,29 @@
+function testBefore(node, parent, type) {
+test(function() {
+assert_true("before" in node);
+assert_equals(typeof node.before, "function");
+assert_equals(node.before.length, 0);
+}, type + " should support before()");
+test(function() {
+var x, y;
+if (type == 'element' || type == 'document-fragment') {
+  x = document.createElement('x');
+  y = document.createElement('y');
+}
+if (type == 'comment') {
+  x = document.createComment('x');
+  y = document.createComment('y');
+}
+if (type == 'text') {
+  x = document.createTextNode('x');
+  y = document.createTextNode('y');
+}
+parent.appendChild(node);
+assert_equals(node.parentNode, parent, "Appended node should have a parent");
+node.before(x, y, 'z');
+assert_equals(parent.childNodes.length, 4, "Parent should have 4 children");
+assert_equals(parent.firstChild, x, "Parent's first child should be x");
+assert_equals(parent.childNodes[2].data, 'z', "Parent's third child's data should be z");
+assert_equals(parent.lastChild, node, "Parent's last child should be node");
+}, "before() should work for " + type);
+}