Very simple version of Isolates.

sdk/lib/_internal/lib/isolate_patch.dart

Index: sdk/lib/_internal/lib/isolate_patch.dart
diff --git a/sdk/lib/_internal/lib/isolate_patch.dart b/sdk/lib/_internal/lib/isolate_patch.dart
index 4e6982ae430082ac93dbca7bab7d55b89829bcea..a51941520f7740eb8fd1ee46f54d479ec9500282 100644
--- a/sdk/lib/_internal/lib/isolate_patch.dart
+++ b/sdk/lib/_internal/lib/isolate_patch.dart
@@ -10,6 +10,16 @@ import 'dart:_isolate_helper' show IsolateNatives,
                                    CloseToken,
                                    JsIsolateSink;
 
+patch class Isolate {
+  patch static Future<Isolate> spawn(void entryPoint(message), var message) {
+    throw new UnimplementedError("spawn");
+  }
+
+  patch static Future<Isolate> spawnUri(Uri uri, var arguments) {
+    throw new UnimplementedError("spawn uri");
+  }
+}
+
 patch class _Isolate {
   patch static ReceivePort get port {
     if (lazyPort == null) {
@@ -18,7 +28,7 @@ patch class _Isolate {
     return lazyPort;
   }
 
-  patch static SendPort spawnFunction(void topLevelFunction(),
+  static SendPort _spawnFunction(void topLevelFunction(),
       [bool unhandledExceptionCallback(IsolateUnhandledException e)]) {
     if (unhandledExceptionCallback != null) {
       // TODO(9012): Implement the UnhandledExceptionCallback.
@@ -33,33 +43,9 @@ patch class _Isolate {
   }
 }
 
-patch bool _isCloseToken(var object) {
-  return identical(object, const CloseToken());
-}
-
 /** Default factory for receive ports. */
 patch class ReceivePort {
   patch factory ReceivePort() {
     return new ReceivePortImpl();
   }
 }
-
-patch class MessageBox {
-  patch MessageBox.oneShot() : this._oneShot(new ReceivePort());
-  MessageBox._oneShot(ReceivePort receivePort)
-      : stream = new IsolateStream._fromOriginalReceivePortOneShot(receivePort),
-        sink = new JsIsolateSink.fromPort(receivePort.toSendPort());
-
-  patch MessageBox() : this._(new ReceivePort());
-  MessageBox._(ReceivePort receivePort)
-      : stream = new IsolateStream._fromOriginalReceivePort(receivePort),
-        sink = new JsIsolateSink.fromPort(receivePort.toSendPort());
-}
-
-patch IsolateSink streamSpawnFunction(
-    void topLevelFunction(),
-    [bool unhandledExceptionCallback(IsolateUnhandledException e)]) {
-  SendPort sendPort = spawnFunction(topLevelFunction,
-                                    unhandledExceptionCallback);
-  return new JsIsolateSink.fromPort(sendPort);
-}