Make pub build use barback.

pkg/barback/lib/src/package_graph.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.package_graph;
 
 import 'dart:async';
 
 import 'asset_cascade.dart';
 import 'asset_id.dart';
@@ skipping 69 matching lines @@
       });
 
       cascade.onLog.listen(_logger.logEntry);
 
       cascade.results.listen((result) {
         _cascadeResults[cascade.package] = result;
         // If any cascade hasn't yet finished, the overall build isn't finished
         // either.
         if (_cascadeResults.values.any((result) => result == null)) return;
 
-        var errors = unionAll(
-            _cascadeResults.values.map((result) => result.errors));
-
-        var numLogErrors = _cascadeResults.values.fold(0,
-            (numErrors, result) => result.numErrors - result.errors.length);
-
         // Include all build errors for all cascades. If no cascades have
         // errors, the result will automatically be considered a success.
-        _resultsController.add(new BuildResult(errors, numLogErrors));
+        _resultsController.add(
+            new BuildResult.aggregate(_cascadeResults.values));
       }, onError: (error) {
         _lastUnexpectedError = error;
         _resultsController.addError(error);
       });
     }
 
     _errors = mergeStreams(_cascades.values.map((cascade) => cascade.errors),
         broadcast: true);
   }
 
@@ skipping 22 matching lines @@
     }
 
     // If an unexpected error occurred, complete with that.
     if (_lastUnexpectedError != null) {
       var error = _lastUnexpectedError;
       _lastUnexpectedError = null;
       return new Future.error(error);
     }
 
     // If the build completed with an error, complete the future with it.
-    var errors = unionAll(
-        _cascadeResults.values.map((result) => result.errors));
-    if (errors.isNotEmpty) {
-      return new Future.error(BarbackException.aggregate(errors));
+    var result = new BuildResult.aggregate(_cascadeResults.values);
+    if (!result.succeeded) {
+      return new Future.error(BarbackException.aggregate(result.errors));
     }
 
     // Otherwise, return all of the final output assets.
     var assets = unionAll(_cascades.values.map(
         (cascade) => cascade.availableOutputs.toSet()));
 
     return new Future.value(new AssetSet.from(assets));
   }
 
   /// Adds [sources] to the graph's known set of source assets.
@@ skipping 16 matching lines @@
       if (cascade == null) throw new ArgumentError("Unknown package $package.");
       cascade.removeSources(ids);
     });
   }
 
   void updateTransformers(String package,
       Iterable<Iterable<Transformer>> transformers) {
     _cascades[package].updateTransformers(transformers);
   }
 }