Very simple version of Isolates.

runtime/vm/custom_isolate_test.cc

Index: runtime/vm/custom_isolate_test.cc
diff --git a/runtime/vm/custom_isolate_test.cc b/runtime/vm/custom_isolate_test.cc
index d64e8366800542c59233c6f691bd56703f4b8da3..7d43473bcbf1c6be10c83bc37da92a1836c92886 100644
--- a/runtime/vm/custom_isolate_test.cc
+++ b/runtime/vm/custom_isolate_test.cc
@@ -24,7 +24,7 @@ static Dart_NativeFunction NativeLookup(Dart_Handle name, int argc);
 static const char* kCustomIsolateScriptChars =
     "import 'dart:isolate';\n"
     "\n"
-    "ReceivePort mainPort;\n"
+    "RawReceivePort mainPort;\n"
     "\n"
     "echo(arg) native \"native_echo\";\n"
     "\n"
@@ -51,21 +51,23 @@ static const char* kCustomIsolateScriptChars =
     "\n"
     "isolateMain() {\n"
     "   echo('Running isolateMain');\n"
-    "   mainPort.receive((message, SendPort replyTo) {\n"
-    "     echo('Received: $message');\n"
-    "     replyTo.send((message + 1), null);\n"
-    "   });\n"
+    "   mainPort.handler = (message) {\n"
+    "     var data = message[0];\n"
+    "     var replyTo = message[1];\n"
+    "     echo('Received: $data');\n"
+    "     replyTo.send(data + 1);\n"
+    "   };\n"
     "}\n"
     "\n"
     "main() {\n"
     "  var isolate = new CustomIsolate(\"isolateMain\");\n"
-    "  var receivePort = new ReceivePort();\n"
+    "  var receivePort = new RawReceivePort();\n"
     "  SendPort port = isolate.spawn();\n"
-    "  port.send(42, receivePort.toSendPort());\n"
-    "  receivePort.receive((message, _) {\n"
+    "  port.send([42, receivePort.sendPort]);\n"
+    "  receivePort.handler = (message) {\n"
     "    receivePort.close();\n"
     "    echo('Received: $message');\n"
-    "  });\n"
+    "  };\n"
     "  return 'success';\n"
     "}\n";