Track async causal stack traces

runtime/observatory/lib/src/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 repositories;
 
 class TargetChangeEvent implements M.TargetChangeEvent {
   final TargetRepository repository;
   final bool disconnected;
   TargetChangeEvent(this.repository, [this.disconnected = false]);
@@ skipping 83 matching lines @@
   SC.WebSocketVMTarget find(String networkAddress) {
     for (SC.WebSocketVMTarget item in _list) {
       if (item.networkAddress == networkAddress) {
         return item;
       }
     }
     return null;
   }
 
   static String _networkAddressOfDefaultTarget() {
+    if (!identical(1, 1.0)) {
+      // Dartium, assume we are developing.
+      return 'ws://127.0.0.1:8181/ws';
+    }
     Uri serverAddress = Uri.parse(window.location.toString());
     return 'ws://${serverAddress.authority}${serverAddress.path}ws';
   }
 }