Add support for native bindings generation to dartgenerator.py.

client/dom/src/native_DOMPublic.dart

+// This API is exploratory.
+spawnDomIsolate(Window targetWindow, String entryPoint) {
+  if (targetWindow is! DOMWindowImplementation && targetWindow is! DOMWindowCrossFrameImplementation) {
+    throw 'Bad window argument: $targetWindow';
+  }
+  final result = new Completer<SendPort>();
+  final port = Utils.spawnDomIsolate(targetWindow, entryPoint);
+  window.setTimeout(() { result.complete(port); }, 0);
+  return result.future;
+}
+
+// layoutTestController implementation.
+// FIXME: provide a separate lib for layoutTestController.
+
+var _layoutTestController;
+
+LayoutTestController get layoutTestController() {
+  if (_layoutTestController === null)
+    _layoutTestController = new LayoutTestController._(NPObject.retrieve("layoutTestController"));
+  return _layoutTestController;
+}
+
+class LayoutTestController {
+  final NPObject _npObject;
+
+  LayoutTestController._(this._npObject);
+
+  dumpAsText() => _npObject.invoke('dumpAsText');
+  notifyDone() => _npObject.invoke('notifyDone');
+  setCanOpenWindows() => _npObject.invoke('setCanOpenWindows');
+  waitUntilDone() => _npObject.invoke('waitUntilDone');
+}