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..8ad378569618eb3dd922e5f140e5eb57a35d47bb 100644
--- a/sdk/lib/_internal/lib/isolate_patch.dart
+++ b/sdk/lib/_internal/lib/isolate_patch.dart
@@ -10,15 +10,26 @@ import 'dart:_isolate_helper' show IsolateNatives,
                                    CloseToken,
                                    JsIsolateSink;
 
-patch class _Isolate {
-  patch static ReceivePort get port {
+patch class Isolate {
+  patch static Future<Isolate> spawn(void entryPoint(message), var message) {
+    throw new UnimplementedError("spawn");
+  }
+
+  patch static Future<Isolate> spawnUri(
+      Uri uri, List<String> args, var message) {
+    throw new UnimplementedError("spawn uri");
+  }
+}
+
+class _Isolate {
+  static ReceivePort get port {
     if (lazyPort == null) {
       lazyPort = new ReceivePort();
     }
     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.
@@ -28,38 +39,24 @@ patch class _Isolate {
     return IsolateNatives.spawnFunction(topLevelFunction);
   }
 
-  patch static SendPort spawnUri(String uri) {
+  static SendPort _spawnUri(String uri) {
     return IsolateNatives.spawn(null, uri, false);
   }
 }
 
-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 factory ReceivePort.fromRawReceivePort(RawReceivePort rawPort) {
+    throw new UnimplementedError("ReceivePort.fromRawReceivePort");
+  }
 }
 
-patch IsolateSink streamSpawnFunction(
-    void topLevelFunction(),
-    [bool unhandledExceptionCallback(IsolateUnhandledException e)]) {
-  SendPort sendPort = spawnFunction(topLevelFunction,
-                                    unhandledExceptionCallback);
-  return new JsIsolateSink.fromPort(sendPort);
-}
+patch class RawReceivePort {
+  patch factory RawReceivePort([void handler(event)]) {
+    throw new UnimplementedError("RawReceivePort");
+  }
+}