Remove AsyncError with Expando.

tests/standalone/debugger/debug_lib.dart

 // Copyright (c) 2013, 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.
 
 // Library used by debugger wire protocol tests (standalone VM debugging).
 
 library DartDebugger;
 
 import "dart:io";
 import "dart:math";
@@ skipping 440 matching lines @@
               print("Unexpected exception:\n$e\n$trace");
               close(killDebugee: true);
             }
           },
           onDone: () {
             print("Connection closed by debug target");
             close(killDebugee: true);
           },
           onError: (e) {
             print("Error '$e' detected in input stream from debug target");
+            var trace = getAttachedStackTrace(e);
+            if (trace != null) print("StackTrace: $trace");
             close(killDebugee: true);
           });
       },
-      onError: (asyncErr) {
-        error("Error while connecting to debugee: $asyncErr");
+      onError: (e) {
+        String msg = "Error while connecting to debugee: $e";
+        var trace = getAttachedStackTrace(e);
+        if (trace != null) msg += "\nStackTrace: $trace";
+        error(msg);
         close(killDebugee: true);
       });
   }
 
   void close({killDebugee: false}) {
     if (errorsDetected) {
       for (int i = 0; i < errors.length; i++) print(errors[i]);
     }
     if (socket != null) socket.close();
     if (killDebugee) {
@@ skipping 35 matching lines @@
           if (exitCode != 0) throw "bad exit code: $exitCode";
           print("Debug target process exited with exit code $exitCode");
         });
         var debugger =
             new Debugger(process, debugPort, new DebugScript(script));
       });
     },
     onError: (e) {
       if (++retries >= 3) { 
         print('unable to find unused port: $e');
+        var trace = getAttachedStackTrace(e);
+        if (trace != null) print("StackTrace: $trace");
         return -1; 
       } else {
         // Retry with another random port.
         RunScript(script);
       }
     });
   return true;
 }