Track async causal stack traces

runtime/observatory/lib/src/models/repositories/target.dart

 // Copyright (c) 2016, 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.
 
 part of models;
 
 abstract class TargetChangeEvent {
   TargetRepository get repository;
 }
 
 abstract class TargetRepository {
   Stream<TargetChangeEvent> get onChange;
 
   Target get current;
   Iterable<Target> list();
   void add(String);
   void setCurrent(Target);
   void delete(Target);
+  Target find(String networkAddress);
 }