Redo StreamTransformers so they work with Stack traces.

pkg/barback/test/stream_pool_test.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.test.stream_pool_test;
 
 import 'dart:async';
 
 import 'package:barback/src/stream_pool.dart';
 import 'package:barback/src/utils.dart';
@@ skipping 32 matching lines @@
       controller1.add("first");
 
       var controller2 = new StreamController<String>();
       pool.add(controller2.stream);
       controller2.add("second");
       controller1.addError("third");
       controller2.addError("fourth");
       controller1.add("fifth");
 
       expect(newFuture(() {
-        return pool.stream.transform(new StreamTransformer(
+        return pool.stream.transform(new StreamTransformer.fromHandlers(
             handleData: (data, sink) => sink.add(["data", data]),
-            handleError: (error, sink) => sink.add(["error", error]))).toList();
+            handleError: (error, stackTrace, sink) {
+          sink.add(["error", error]);
+        })).toList();
       }), completion(equals([
         ["data", "first"],
         ["data", "second"],
         ["error", "third"],
         ["error", "fourth"],
         ["data", "fifth"]
       ])));
 
       pumpEventQueue().then((_) => pool.close());
     });
@@ skipping 38 matching lines @@
 
       var controller1 = new StreamController<String>.broadcast();
       pool.add(controller1.stream);
       controller1.addError("first");
 
       var controller2 = new StreamController<String>.broadcast();
       pool.add(controller2.stream);
       controller2.addError("second");
 
       expect(newFuture(() {
-        return pool.stream.transform(new StreamTransformer(
+        return pool.stream.transform(new StreamTransformer.fromHandlers(
             handleData: (data, sink) => sink.add(data),
-            handleError: (error, sink) => sink.add(error))).toList();
+            handleError: (error, stackTrace, sink) { sink.add(error); }))
+            .toList();
       }), completion(isEmpty));
 
       pumpEventQueue().then((_) => pool.close());
     });
 
     test("doesn't buffer inputs from a buffered stream", () {
       var pool = new StreamPool<String>.broadcast();
       var controller = new StreamController<String>();
       pool.add(controller.stream);
       controller.add("first");
@@ skipping 80 matching lines @@
           return pumpEventQueue();
         }).then((_) {
           pool.remove(broadcastController.stream);
           broadcastController.add("fourth");
           pool.close();
         }), completes);
       });
     });
   }
 }