Ensure that errors have stack traces attached.

sdk/lib/_internal/pub/lib/src/barback/server.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 pub.barback.server;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
@@ skipping 112 matching lines @@
         request.response.statusCode = 500;
         request.response.reasonPhrase = "Internal Error";
         request.response.write(error);
         request.response.close();
       });
     }).catchError((error, trace) {
       if (error is! AssetNotFoundException) {
         trace = new Trace.from(trace);
         _logRequest(request, "$error\n$trace");
 
-        _resultsController.addError(error);
+        _resultsController.addError(error, trace);
         close();
         return;
       }
 
       _resultsController.add(
           new BarbackServerResult._failure(request.uri, id, error));
       _notFound(request, error);
     });
   }
 
@@ skipping 57 matching lines @@
               socket.add(JSON.encode({"path": urlPath}));
             } on FormatException catch (ex) {
               _webSocketError(socket, ex.message);
             }
             break;
 
           default:
             _webSocketError(socket, 'Unknown command "${command["command"]}".');
             break;
         }
-      }, onError: (error) {
-        _resultsController.addError(error);
-      }, cancelOnError: true);
-    }).catchError((error) {
-      _resultsController.addError(error);
-    });
+      }, onError: _resultsController.addError, cancelOnError: true);
+    }).catchError(_resultsController.addError);
   }
 
   /// Converts a [url] served by pub serve into an [AssetId] that can be
   /// requested from barback.
   AssetId _urlToId(Uri url) {
     var id = specialUrlToId(url);
     if (id != null) return id;
 
     // Otherwise, it's a path in current package's web directory.
     var parts = path.url.split(url.path);
@@ skipping 54 matching lines @@
   bool get isSuccess => error == null;
 
   /// Whether the request was served unsuccessfully.
   bool get isFailure => !isSuccess;
 
   BarbackServerResult._success(this.url, this.id)
       : error = null;
 
   BarbackServerResult._failure(this.url, this.id, this.error);
 }