Remove deprecated parts of dart:async.

sdk/lib/_internal/pub/lib/src/barback/load_transformers.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 pub.load_transformers;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:isolate';
 
@@ skipping 361 matching lines @@
   /// [error] should be the result of [CrossIsolateException.serialize].
   CrossIsolateException.deserialize(Map error)
       : type = error['type'],
         message = error['message'],
         stackTrace = error['stack'] == null ? null :
             new Trace.parse(error['stack']);
 
   /// Serializes [error] to a map that can safely be passed across isolate
   /// boundaries.
   static Map serialize(error, [StackTrace stack]) {
-    if (stack == null) stack = getAttachedStackTrace(error);
+    if (stack == null && error is Error) stack = error.stackTrace;
     return {
       'type': error.runtimeType.toString(),
       'message': getErrorMessage(error),
       'stack': stack == null ? null : stack.toString()
     };
   }
 
   String toString() => "\$message\\n\$stackTrace";
 }
 
@@ skipping 308 matching lines @@
     'replyTo': receivePort.sendPort
   });
 
   return receivePort.first.then((response) {
     if (response['type'] == 'success') return response['value'];
     assert(response['type'] == 'error');
     return new Future.error(
         new dart.CrossIsolateException.deserialize(response['error']));
   });
 }