fixes #173, ability to use native JS indexers

test/codegen/sunflower/dom.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 @JsName(name: 'window')
 library dom;
 
 
 class JsName {
   /// The JavaScript name.
   /// Used for classes and libraries.
   /// Note that this could be an expression, e.g. `lib.TypeName` in JS, but it
   /// should be kept simple, as it will be generated directly into the code.
   final String name;
   const JsName({this.name});
 }
 class Overload {
   const Overload();
 }
 const overload = const Overload();
 
 external Document get document;
 
 @JsName(name: 'Document')
 abstract class Document {
+  Element createElement(String name);
   Element querySelector(String selector);
 }
 
 @JsName(name: 'Element')
 abstract class Element {
   void addEventListener(String type, EventListener callback, [bool capture]);
   String textContent;
+  NodeList get childNodes;
+}
+
+@JsName()
+class Node {}
+
+@JsName()
+class NodeList {
+  external NodeList();
+  external num get length;
+  external set length(num _);
+  external Node item(num index);
+
+  external Node operator [](num index);
+  external void operator []=(num index, Node);
 }
 
 typedef void EventListener(Event e);
 
+@JsName()
 abstract class Event {}
 
 @JsName(name: 'HTMLInputElement')
 abstract class InputElement extends Element {
   String value;
 }
 
 @JsName(name: 'HTMLCanvasElement')
 abstract class CanvasElement extends Element {
   RenderingContext getContext(String contextId);
@@ skipping 135 matching lines @@
 abstract class TextMetrics {
   num get width;
 }
 
 @JsName()
 abstract class ImageData {
   int get width;
   int get height;
   // TODO: readonly Uint8ClampedArray data;
 }