Better suqpport for async VM frames.

lib/src/vm_trace.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 vm_trace;
 
 import 'frame.dart';
 import 'utils.dart';
 
 /// An implementation of [StackTrace] that emulates the behavior of the VM's
 /// implementation.
 ///
 /// In particular, when [toString] is called, this returns a string in the VM's
 /// stack trace format.
 class VMTrace implements StackTrace {
   /// The stack frames that comprise this stack trace.
   final List<Frame> frames;
 
   VMTrace(this.frames);
 
   String toString() {
     var i = 1;
     return frames.map((frame) {
       var number = padRight("#${i++}", 8);
-      var member = frame.member.replaceAll("<fn>", "<anonymous closure>");
+      var member = frame.member
+          .replaceAll("<fn>", "<anonymous closure>")
+          .replaceAll("<async>", "<<anonymous closure>_async_body>");
       var line = frame.line == null ? 0 : frame.line;
       var column = frame.column == null ? 0 : frame.column;
       return "$number$member (${frame.uri}:$line:$column)\n";
     }).join();
   }
 }