Remove AsyncError with Expando.

tools/ddbg.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.
 
 // Simple interactive debugger shell that connects to the Dart VM's debugger
 // connection port.
 
 import "dart:io";
 import "dart:json" as json;
 import "dart:utf";
@@ skipping 557 matching lines @@
     vmSubscription = stringStream.listen(
         (String data) {
           processVmData(data);
         },
         onDone: () {
           print("VM debugger connection closed");
           quitShell();
         },
         onError: (err) {
           print("Error in debug connection: $err");
+          // TODO(floitsch): do we want to print the stack trace?
           quitShell();
         });
     stdinSubscription = stdin.transform(new StringDecoder())
                              .transform(new LineTransformer())
                              .listen((String line) => processCommand(line));
   });
 }
 
 void main() {
   Options options = new Options();
   List<String> arguments = options.arguments;
   if (arguments.length > 0) {
     arguments = <String>['--debug', '--verbose_debug']..addAll(arguments);
     Process.start(options.executable, arguments).then((Process process) {
       process.stdin.close();
       process.exitCode.then((int exitCode) {
         print('${arguments.join(" ")} exited with $exitCode');
       });
       debuggerMain();
     });
   } else {
     debuggerMain();
   }
 }