Add chain support to barback.

pkg/barback/lib/src/build_result.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.build_result;
 
-import 'dart:async';
-
-import 'package:stack_trace/stack_trace.dart';
-
 import 'errors.dart';
 import 'utils.dart';
 
 /// An event indicating that the cascade has finished building all assets.
 ///
 /// A build can end either in success or failure. If there were no errors during
 /// the build, it's considered to be a success; any errors render it a failure,
 /// although individual assets may still have built successfully.
 class BuildResult {
   // TODO(rnystrom): Revise how to track error results. Errors can come from
@@ skipping 21 matching lines @@
     var errors = unionAll(results.map((result) => result.errors));
     return new BuildResult(errors);
   }
 
   String toString() {
     if (succeeded) return "success";
 
     return "errors:\n" + errors.map((error) {
       var stackTrace = null;
       if (error is TransformerException || error is AssetLoadException) {
-        stackTrace = new Trace.from(error.stackTrace);
+        stackTrace = error.stackTrace.terse;
       }
 
       var msg = new StringBuffer();
       msg.write(prefixLines(error.toString()));
       if (stackTrace != null) {
         msg.write("\n\n");
-        msg.write("Stack trace:\n");
+        msg.write("Stack chain:\n");
         msg.write(prefixLines(stackTrace.toString()));
       }
       return msg.toString();
     }).join("\n\n");
   }
 }