Roll Observatory packages and add a roll script

packages/barback/lib/src/graph/phase_output.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 barback.graph.phase_output;
 
 import 'dart:async';
 import 'dart:collection';
 
 import '../asset/asset_forwarder.dart';
@@ skipping 94 matching lines @@
       // they've successfully resolved the collision or not.
       if (_assets.length > 1) {
         // TODO(nweiz): report this through the output asset.
         _phase.cascade.reportError(collisionException);
       }
     });
   }
 
   String toString() => "phase output in $_location for $output";
 }