Implement ParentNode IDL interface

Source/core/dom/Element.idl

Index: Source/core/dom/Element.idl
diff --git a/Source/core/dom/Element.idl b/Source/core/dom/Element.idl
index 76136bc0e735762cdb5860b766207bb256b4f9df..64b4338454563bbd1720cac1d3799cebf3e8bf05 100644
--- a/Source/core/dom/Element.idl
+++ b/Source/core/dom/Element.idl
@@ -101,12 +101,15 @@
     // WebKit extension, pending specification.
     [RaisesException] boolean webkitMatchesSelector([Default=Undefined] optional DOMString selectors);
 
-    // ElementTraversal API
+    // ParentNode interface API
+    [PerWorldBindings] readonly attribute HTMLCollection children;
     [PerWorldBindings] readonly attribute Element firstElementChild;
     [PerWorldBindings] readonly attribute Element lastElementChild;
+    [PerWorldBindings] readonly attribute unsigned long childElementCount;
+
+    // ElementTraversal API
     [PerWorldBindings] readonly attribute Element previousElementSibling;
     [PerWorldBindings] readonly attribute Element nextElementSibling;
-    [PerWorldBindings] readonly attribute unsigned long childElementCount;
 
     // ShadowAware API
     [Reflect=pseudo, ImplementedAs=pseudo, PerWorldBindings] attribute DOMString webkitPseudo;