Step one towards stable error messages with details:

pkg/polymer/lib/src/build/build_log_combiner.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.
 
 /// Logic to combine all the ._buildLog.* logs into one ._buildLog file.
 library polymer.src.build.log_combiner;
 
 import 'dart:async';
 
 import 'package:barback/barback.dart';
+import 'package:code_transformers/messages/build_logger.dart';
 import 'package:html5lib/parser.dart' show parseFragment;
 
 import 'common.dart';
-import 'wrapped_logger.dart';
 
 /// Logic to combine all the ._buildLog.* logs into one ._buildLog file.
 class BuildLogCombiner extends Transformer with PolymerTransformer {
   final TransformOptions options;
 
   BuildLogCombiner(this.options);
 
   /// Run only on entry point html files and only if
   /// options.injectBuildLogsInOutput is true.
   bool isPrimary(idOrAsset) {
     if (!options.injectBuildLogsInOutput) return false;
     var id = idOrAsset is AssetId ? idOrAsset : idOrAsset.id;
     return options.isHtmlEntryPoint(id);
   }
 
   Future apply(Transform transform) {
     // Combine all ._buildLogs* files into one ._buildLogs file.
-    return WrappedLogger.combineLogFiles(transform);
+    return BuildLogger.combineLogFiles(transform);
   }
 }