Don't limit transformer parallelism in barback.

pkg/barback/lib/src/transform_node.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.transform_node;
 
 import 'dart:async';
 
 import 'package:source_maps/span.dart';
 
@@ skipping 110 matching lines @@
 
     // Clear all the old input subscriptions. If an input is re-used, we'll
     // re-subscribe.
     for (var subscription in _inputSubscriptions.values) {
       subscription.cancel();
     }
     _inputSubscriptions.clear();
 
     _isDirty = false;
 
-    return phase.cascade.graph.transformPool
-        .withResource(() => transformer.apply(transform))
-        .catchError((error, stack) {
+    return transformer.apply(transform).catchError((error, stack) {
       // If the transform became dirty while processing, ignore any errors from
       // it.
       if (_isDirty) return;
 
       if (error is! MissingInputException) {
         error = new TransformerException(info, error, stack);
       }
 
       // Catch all transformer errors and pipe them to the results stream.
       // This is so a broken transformer doesn't take down the whole graph.
@@ skipping 71 matching lines @@
     return brandNewOutputs;
   }
 
   void _log(AssetId asset, LogLevel level, String message, Span span) {
     // If the log isn't already associated with an asset, use the primary.
     if (asset == null) asset = primary.id;
     var entry = new LogEntry(info, asset, level, message, span);
     _onLogController.add(entry);
   }
 }