Redo StreamTransformers so they work with Stack traces.

pkg/http_server/lib/src/http_body_impl.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.
 
 part of http_server;
 
 class _HttpBodyHandlerTransformer
-    extends StreamEventTransformer<HttpRequest, HttpRequestBody> {
+    implements StreamTransformer<HttpRequest, HttpRequestBody> {
   final Encoding _defaultEncoding;
-  _HttpBodyHandlerTransformer(this._defaultEncoding);
 
-  void handleData(HttpRequest request, EventSink<HttpRequestBody> sink) {
-    _HttpBodyHandler.processRequest(request, _defaultEncoding)
-        .then(sink.add, onError: sink.addError);
+  const _HttpBodyHandlerTransformer(this._defaultEncoding);
+
+  Stream<HttpRequestBody> bind(Stream<HttpRequest> stream) {
+    return new Stream<HttpRequestBody>.eventTransformed(
+        stream,
+        (EventSink<HttpRequestBody> sink) =>
+            new _HttpBodyHandlerTransformerSink(_defaultEncoding, sink));
   }
 }
 
+class _HttpBodyHandlerTransformerSink implements EventSink<HttpRequest> {
+  final Encoding _defaultEncoding;
+  final EventSink<HttpRequestBody> _outSink;
+
+  _HttpBodyHandlerTransformerSink(this._defaultEncoding, this._outSink);
+
+  void add(HttpRequest request) {
+    _HttpBodyHandler.processRequest(request, _defaultEncoding)
+        .then(_outSink.add, onError: _outSink.addError);
+  }
+  void addError(Object error, [StackTrace stackTrace]) {
+    _outSink.addError(error, stackTrace);
+  }
+  void close() => _outSink.close();
+}
+
 class _HttpBodyHandler {
   static Future<HttpRequestBody> processRequest(
       HttpRequest request,
       Encoding defaultEncoding) {
     return process(request, request.headers, defaultEncoding)
         .then((body) => new _HttpRequestBody(request, body),
               onError: (error) {
                 // Try to send BAD_REQUEST response.
                 request.response.statusCode = HttpStatus.BAD_REQUEST;
                 request.response.close();
@@ skipping 162 matching lines @@
   _HttpClientResponseBody(HttpClientResponse response, HttpBody body)
       : super(body.contentType, body.type, body.body),
         this.response = response;
 
   int get statusCode => response.statusCode;
 
   String get reasonPhrase => response.reasonPhrase;
 
   HttpHeaders get headers => response.headers;
 }