Very simple version of Isolates.

runtime/bin/socket_patch.dart

Index: runtime/bin/socket_patch.dart
diff --git a/runtime/bin/socket_patch.dart b/runtime/bin/socket_patch.dart
index a0de4fd122c9b5aa03405d85c8deaac8fe312b1a..458da76d77d38aa67a7903ecc33244cf7308e8a9 100644
--- a/runtime/bin/socket_patch.dart
+++ b/runtime/bin/socket_patch.dart
@@ -206,7 +206,7 @@ class _NativeSocket extends NativeFieldWrapperClass1 {
   // Handlers and receive port for socket events from the event handler.
   int eventMask = 0;
   List eventHandlers;
-  ReceivePort eventPort;
+  RawReceivePort eventPort;
 
   // Indicates if native interrupts can be activated.
   bool canActivateEvents = true;
@@ -588,8 +588,7 @@ class _NativeSocket extends NativeFieldWrapperClass1 {
 
   void connectToEventHandler() {
     if (eventPort == null) {
-      eventPort = new ReceivePort();
-      eventPort.receive ((var message, _) => multiplex(message));
+      eventPort = new RawReceivePort(multiplex);
     }
   }