Dart: Use a RawReceivePort to receive events for Mojo handles.

benchmarks/mojo_rtt_benchmark/lib/isolate.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This Mojo app is a benchmark of Dart <=> Dart IPC Round Trip Times.
 // To run it:
 //
 // $ ./mojo/devtools/common/mojo_benchmark [--release] mojo/tools/data/rtt_benchmarks
 
 import 'dart:async';
@@ skipping 77 matching lines @@
 
   _isolateMessageHandler(msg) {
     if (msg is SendPort) {
       _sendPortCompleter.complete(msg);
     } else {
       var completer = _completers.removeAt(0);
       completer.complete(null);
     }
   }
 
-  void _errorHandler() {
+  void _errorHandler(Object e) {
     _doEcho = false;
     _receivePort.close();
     MojoHandle.reportLeakedHandles();
   }
 }
 
 main(List args) {
   MojoHandle appHandle = new MojoHandle(args[0]);
   new IsolateMessageApp.fromHandle(appHandle);
 }