Defer execution of the main isolate's entry point until the message loop.

runtime/lib/isolate_patch.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import "dart:collection" show HashMap;
 
 patch class ReceivePort {
   /* patch */ factory ReceivePort() = _ReceivePortImpl;
 
   /* patch */ factory ReceivePort.fromRawReceivePort(RawReceivePort rawPort) =
@@ skipping 162 matching lines @@
 
   // Forward the implementation of sending messages to the VM.
   void _sendInternal(var message) native "SendPortImpl_sendInternal_";
 }
 
 typedef _MainFunction();
 typedef _MainFunctionArgs(args);
 typedef _MainFunctionArgsMessage(args, message);
 
 /**
+ * Takes the real entry point as argument and invokes it with the
+ * initial message.  Defers execution of the entry point until the
+ * isolate is in the message loop.
+ */
+void _startMainIsolate(Function entryPoint,
+                       List<String> args) {
+  RawReceivePort port = new RawReceivePort();
+  port.handler = (_) {
+    port.close();
+    _startIsolate(null,   // no parent port
+                  entryPoint,
+                  args,
+                  null,   // no message
+                  true,   // isSpawnUri
+                  null,   // no control port
+                  null);  // no capabilities
+  };
+  port.sendPort.send(null);
+}
+
+/**
  * Takes the real entry point as argument and invokes it with the initial
  * message.
- *
- * The initial startup message is received through the control port.
  */
 void _startIsolate(SendPort parentPort,
                    Function entryPoint,
                    List<String> args,
                    var message,
                    bool isSpawnUri,
                    RawReceivePort controlPort,
                    List capabilities) {
   if (controlPort != null) {
     controlPort.handler = (_) {};  // Nobody home on the control port.
@@ skipping 141 matching lines @@
   }
 
   /* patch */ void addErrorListener(SendPort port) {
     throw new UnsupportedError("addErrorListener");
   }
 
   /* patch */ void removeErrorListener(SendPort port) {
     throw new UnsupportedError("removeErrorListener");
   }
 }