Implement spawnDomFunction

lib/dom/src/native_DOMPublic.dart

Index: lib/dom/src/native_DOMPublic.dart
diff --git a/lib/dom/src/native_DOMPublic.dart b/lib/dom/src/native_DOMPublic.dart
index fe76bea11d339f31e90d2ea4029d45bca0f21a49..9bfac9e241c2421f767bf4fee71ebe4317c3c255 100644
--- a/lib/dom/src/native_DOMPublic.dart
+++ b/lib/dom/src/native_DOMPublic.dart
@@ -3,15 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 // This API is exploratory.
-spawnDomIsolate(Window targetWindow, String entryPoint) {
-  if (targetWindow is! _DOMWindowImpl && targetWindow is! _DOMWindowCrossFrameImpl) {
-    throw 'Bad window argument: $targetWindow';
-  }
-  final result = new Completer<SendPort>();
-  final port = _Utils.spawnDomIsolateImpl(targetWindow, entryPoint);
-  window.setTimeout(() { result.complete(port); }, 0);
-  return result.future;
-}
+spawnDomFunction(Function topLevelFunction) => _Utils.spawnDomFunctionImpl(topLevelFunction);
 
 // layoutTestController implementation.
 // FIXME: provide a separate lib for layoutTestController.