fixes #221, initial sync*, async, async* implementation

test/browser/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;
-
-@JsName()
-class Window {}
-
-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;
-external Window get window;
-
-@JsName()
-abstract class Document extends Node {
-  Element createElement(String name);
-  Element querySelector(String selector);
-
-  HTMLElement head;
-  HTMLElement body;
-}
-
-@JsName()
-class Blob {
-  external Blob(blobParts, {String type});
-}
-
-@JsName()
-class CustomEvent {
-  external CustomEvent(String type, {detail, bubbles, cancelable});
-}
-
-@JsName()
-abstract class Element extends Node {
-  void addEventListener(String type, EventListener callback, [bool capture]);
-  String textContent;
-}
-
-@JsName()
-abstract class HTMLElement extends Element {
-  String innerHTML;
-  HTMLCollection get children;
-}
-
-@JsName()
-abstract class Node {
-  bool hasChildNodes();
-  NodeList get childNodes;
-
-  Node insertBefore(Node node, [Node child]);
-  Node appendChild(Node node);
-  Node replaceChild(Node node, Node child);
-  Node removeChild(Node child);
-}
-
-@JsName()
-abstract class HTMLCollection {
-  int get length;
-  external Element operator [](num index);
-}
-
-@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 {}
-
-// TODO(jmesserly): rename these
-@JsName(name: 'HTMLInputElement')
-abstract class InputElement extends HTMLElement {
-  String value;
-}
-
-@JsName(name: 'HTMLCanvasElement')
-abstract class CanvasElement extends HTMLElement {
-  RenderingContext getContext(String contextId);
-}
-
-@JsName(name: 'HTMLDivElement')
-abstract class DivElement extends HTMLElement {
-  RenderingContext getContext(String contextId);
-}
-
-@JsName(name: 'HTMLScriptElement')
-abstract class ScriptElement extends HTMLElement {
-  String type;
-}
-
-
-// TODO(jmesserly): union type of CanvasRenderingContext2D and
-// WebGLRenderingContext
-abstract class RenderingContext {}
-
-// http://www.w3.org/html/wg/drafts/2dcontext/html5_canvas_CR/
-@JsName()
-abstract class CanvasRenderingContext2D
-    implements CanvasDrawingStyles, CanvasPathMethods, RenderingContext {
-
-  // back-reference to the canvas
-  CanvasElement get canvas;
-
-  // state
-  void save(); // push state on state stack
-  void restore(); // pop state stack and restore state
-
-  // transformations (default transform is the identity matrix)
-  void scale(num x, num y);
-  void rotate(num angle);
-  void translate(num x, num y);
-  void transform(num a, num b, num c, num d, num e, num f);
-  void setTransform(num a, num b, num c, num d, num e, num f);
-
-  // compositing
-  num globalAlpha; // (default 1.0)
-  String globalCompositeOperation; // (default source-over)
-
-  // colors and styles (see also the CanvasDrawingStyles interface)
-  Object strokeStyle; // (default black)
-  Object fillStyle; // (default black)
-  CanvasGradient createLinearGradient(num x0, num y0, num x1, num y1);
-  CanvasGradient createRadialGradient(
-      num x0, num y0, num r0, num x1, num y1, num r1);
-  CanvasPattern createPattern(Element image, [String repetition]);
-
-  // shadows
-  num shadowOffsetX; // (default 0)
-  num shadowOffsetY; // (default 0)
-  num shadowBlur; // (default 0)
-  String shadowColor; // (default transparent black)
-
-  // rects
-  void clearRect(num x, num y, num w, num h);
-  void fillRect(num x, num y, num w, num h);
-  void strokeRect(num x, num y, num w, num h);
-
-  // path API (see also CanvasPathMethods)
-  void beginPath();
-  void fill();
-  void stroke();
-  void drawFocusIfNeeded(Element element);
-  void clip();
-  bool isPointInPath(num x, num y);
-
-  // text (see also the CanvasDrawingStyles interface)
-  void fillText(String text, num x, num y, [num maxWidth]);
-  void strokeText(String text, num x, num y, [num maxWidth]);
-  TextMetrics measureText(String text);
-
-  // drawing images
-  void drawImage(Element image, num dx_or_sx, num dy_or_sy,
-      [num dw_or_sw, num dh_or_sh, num dx, num dy, num dw, num dh]);
-  @overload void _drawImage_0(Element image, num dx, num dy);
-  @overload void _drawImage_1(Element image, num dx, num dy, num dw, num dh);
-  @overload void _drawImage_2(Element image, num sx, num sy, num sw, num sh,
-      num dx, num dy, num dw, num dh);
-
-  // hit regions
-  void addHitRegion({String id: '', Element control});
-  void removeHitRegion(String id);
-  void clearHitRegions();
-
-  // pixel manipulation
-  ImageData createImageData(Object sw_or_imageData, [num sh]);
-  @overload ImageData _createImageData_0(num sw, num sh);
-  @overload ImageData _createImageData_1(ImageData imagedata);
-
-  ImageData getImageData(num sx, num sy, num sw, num sh);
-  void putImageData(ImageData imagedata, num dx, num dy,
-      [num dirtyX, num dirtyY, num dirtyWidth, num dirtyHeight]);
-  @overload void _putImageData_0(ImageData imagedata, num dx, num dy,
-      num dirtyX, num dirtyY, num dirtyWidth, num dirtyHeight);
-  @overload void _putImageData_1(ImageData imagedata, num dx, num dy);
-}
-
-abstract class CanvasDrawingStyles {
-  // line caps/joins
-  num lineWidth; // (default 1)
-  String lineCap; // "butt", "round", "square" (default "butt")
-  String lineJoin; // "round", "bevel", "miter" (default "miter")
-  num miterLimit; // (default 10)
-
-  // dashed lines
-  void setLineDash(List<num> segments); // default empty
-  List<num> getLineDash();
-  num lineDashOffset;
-
-  // text
-  String font; // (default 10px sans-serif)
-
-  // "start", "end", "left", "right", "center" (default: "start")
-  String textAlign;
-
-  // "top", "hanging", "middle", "alphabetic",
-  // "ideographic", "bottom" (default: "alphabetic")
-  String textBaseline;
-}
-
-abstract class CanvasPathMethods {
-  // shared path API methods
-  void closePath();
-  void moveTo(num x, num y);
-  void lineTo(num x, num y);
-  void quadraticCurveTo(num cpx, num cpy, num x, num y);
-  void bezierCurveTo(num cp1x, num cp1y, num cp2x, num cp2y, num x, num y);
-  void arcTo(num x1, num y1, num x2, num y2, num radius);
-  void rect(num x, num y, num w, num h);
-  void arc(num x, num y, num radius, num startAngle, num endAngle,
-      [bool anticlockwise]);
-}
-
-@JsName()
-abstract class CanvasGradient {
-  // opaque object
-  void addColorStop(num offset, String color);
-}
-
-@JsName()
-abstract class CanvasPattern {
-  // opaque object
-}
-
-@JsName()
-abstract class TextMetrics {
-  num get width;
-}
-
-@JsName()
-abstract class ImageData {
-  int get width;
-  int get height;
-  // TODO: readonly Uint8ClampedArray data;
-}