Remove AsyncError with Expando.

sdk/lib/_internal/compiler/implementation/dart2js.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 dart2js;
 
 import 'dart:async';
 import 'dart:collection' show Queue, LinkedHashMap;
 import 'dart:io';
 import 'dart:uri';
@@ skipping 326 matching lines @@
   final EventSink<String> sink;
   int count = 0;
 
   CountingSink(this.sink);
 
   void add(String value) {
     sink.add(value);
     count += value.length;
   }
 
-  void addError(AsyncError error) { sink.addError(error); }
+  void addError(Object error) { sink.addError(error); }
 
   void close() { sink.close(); }
 }
 
 class AbortLeg {
   final message;
   AbortLeg(this.message);
   toString() => 'Aborted due to --throw-on-error: $message';
 }
 
@@ skipping 155 matching lines @@
       print(trace);
     } finally {
       exit(253); // 253 is recognized as a crash by our test scripts.
     }
   }
 }
 
 void main() {
   mainWithErrorHandler(new Options());
 }