Fix bugs in HttpBody detected by the analyzer

sdk/lib/io/http_body.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;
 
 
 /**
  * [HttpBodyHandler] is a helper class for parsing and collecting HTTP message
  * data in an easy-to-use [HttpBody] object. The content body is parsed,
@@ skipping 21 matching lines @@
  *         });
  *
  * The following mime-types will be handled specially:
  *   - text/\*
  *   - application/json
  *
  * All other mime-types will be returned as [List<int>].
  */
 class HttpBodyHandler
     implements StreamTransformer<HttpRequest, HttpRequestBody> {
-  factory HttpBodyHandler() => new _HttpBodyHandler();
+  var _transformer;
+
+  HttpBodyHandler() : _transformer = new _HttpBodyHandlerTransformer();
 
   /**
    * Process and parse an incoming [HttpRequest]. The returned [HttpRequestBody]
    * contains a [response] field for accessing the [HttpResponse].
    */
   static Future<HttpRequestBody> processRequest(HttpRequest request) {
     return _HttpBodyHandler.processRequest(request);
   }
 
   /**
    * Process and parse an incoming [HttpClientResponse].
    */
   static Future<HttpClientResponseBody> processResponse(
       HttpClientResponse response) {
     return _HttpBodyHandler.processResponse(response);
   }
+
+  Stream<HttpRequestBody> bind(Stream<HttpRequest> stream) {
+    return _transformer.bind(stream);
+  }
 }
 
 
 /**
  * A HTTP content body produced by [HttpBodyHandler] for either [HttpRequest]
  * or [HttpClientResponse].
  */
 abstract class HttpBody {
   /**
    * The content type e.g. application/json, application/octet-stream,
@@ skipping 61 matching lines @@
   /**
    * Returns the request headers.
    */
   HttpHeaders get headers;
 
   /**
    * The [HttpResponse] used for responding to the client.
    */
   HttpResponse get response;
 }