Implement override checks.

dart/lib/isolate/frog/ports.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.
 
 /** Common functionality to all send ports. */
 class _BaseSendPort implements SendPort {
   /** Id for the destination isolate. */
   final int _isolateId;
 
   const _BaseSendPort(this._isolateId);
 
-  static void checkReplyTo(SendPort replyTo) {
+  void _checkReplyTo(SendPort replyTo) {
     if (replyTo !== null
         && replyTo is! _NativeJsSendPort
         && replyTo is! _WorkerSendPort
         && replyTo is! _BufferingSendPort) {
       throw new Exception("SendPort.send: Illegal replyTo port type");
     }
   }
 
   Future call(var message) {
     final completer = new Completer();
@@ skipping 16 matching lines @@
 }
 
 /** A send port that delivers messages in-memory via native JavaScript calls. */
 class _NativeJsSendPort extends _BaseSendPort implements SendPort {
   final _ReceivePortImpl _receivePort;
 
   const _NativeJsSendPort(this._receivePort, int isolateId) : super(isolateId);
 
   void send(var message, [SendPort replyTo = null]) {
     _waitForPendingPorts([message, replyTo], () {
-      checkReplyTo(replyTo);
+      _checkReplyTo(replyTo);
       // Check that the isolate still runs and the port is still open
       final isolate = _globalState.isolates[_isolateId];
       if (isolate == null) return;
       if (_receivePort._callback == null) return;
 
       // We force serialization/deserialization as a simple way to ensure
       // isolate communication restrictions are respected between isolates that
       // live in the same worker. [_NativeJsSendPort] delivers both messages
       // from the same worker and messages from other workers. In particular,
       // messages sent from a worker via a [_WorkerSendPort] are received at
@@ skipping 29 matching lines @@
 // TODO(eub): abstract this for iframes.
 class _WorkerSendPort extends _BaseSendPort implements SendPort {
   final int _workerId;
   final int _receivePortId;
 
   const _WorkerSendPort(this._workerId, int isolateId, this._receivePortId)
       : super(isolateId);
 
   void send(var message, [SendPort replyTo = null]) {
     _waitForPendingPorts([message, replyTo], () {
-      checkReplyTo(replyTo);
+      _checkReplyTo(replyTo);
       final workerMessage = _serializeMessage({
           'command': 'message',
           'port': this,
           'msg': message,
           'replyTo': replyTo});
 
       if (_globalState.isWorker) {
         // communication from one worker to another go through the main worker:
         _globalState.mainManager.postMessage(workerMessage);
       } else {
@@ skipping 134 matching lines @@
     // map.getValues().forEach(_dispatch);
     map.getValues().forEach((e) => _dispatch(e));
   }
 
   visitBufferingSendPort(_BufferingSendPort port) {
     if (port._port == null) {
       ports.add(port._futurePort);
     }
   }
 }