Fix bugs in HttpBody detected by the analyzer

sdk/lib/io/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 dart.io;
 
 class _HttpBodyHandlerTransformer
     extends StreamEventTransformer<HttpRequest, HttpRequestBody> {
   void handleData(HttpRequest request, EventSink<HttpRequestBody> sink) {
     HttpBodyHandler.processRequest(request)
         .then(sink.add, onError: sink.addError);
   }
 }
 
-class _HttpBodyHandler implements HttpBodyHandler {
-  Stream<HttpRequestBody> bind(Stream<HttpRequest> stream) {
-    return new _HttpBodyHandlerTransformer().bind(stream);
-  }
-
+class _HttpBodyHandler {
   static Future<HttpRequestBody> processRequest(HttpRequest request) {
     return process(request, request.headers)
         .then((body) => new _HttpRequestBody(request, body),
               onError: (error) {
                 // Try to send BAD_REQUEST response.
                 request.response.statusCode = HttpStatus.BAD_REQUEST;
                 request.response.close();
                 request.response.done.catchError((_) {});
                 throw error;
               });
@@ skipping 73 matching lines @@
   _HttpRequestBody(HttpRequest request, HttpBody body)
       : super(body.mimeType, body.type, body.body),
         method = request.method,
         uri = request.uri,
         headers = request.headers,
         response = request.response;
 }
 
 class _HttpClientResponseBody
     extends _HttpBody implements HttpClientResponseBody {
-  final int statusCode;
-  final String reasonPhrase;
-  final HttpHeaders headers;
+  final HttpClientResponse response;
 
   _HttpClientResponseBody(HttpClientResponse response, HttpBody body)
       : super(body.mimeType, body.type, body.body),
-        statusCode = response.statusCode,
-        reasonPhrase = response.reasonPhrase,
-        headers = response.headers;
+        this.response = response;
+
+  int get statusCode => response.statusCode;
+
+  String get reasonPhrase => response.reasonPhrase;
+
+  HttpHeaders get headers => response.headers;
 }