Fix issues found by analyzer.

lib/io/http.dart

 // Copyright (c) 2012, 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.
 
 /**
  * HTTP status codes.
  */
 abstract class HttpStatus {
   static const int CONTINUE = 100;
   static const int SWITCHING_PROTOCOLS = 101;
@@ skipping 48 matching lines @@
   factory HttpServer() => new _HttpServer();
 
   /**
    * Start listening for HTTP requests on the specified [host] and
    * [port]. If a [port] of 0 is specified the server will choose an
    * ephemeral port. The optional argument [backlog] can be used to
    * specify the listen backlog for the underlying OS listen
    * setup. See [addRequestHandler] and [defaultRequestHandler] for
    * information on how incoming HTTP requests are handled.
    */
-  void listen(String host, int port, [int backlog]);
+  void listen(String host, int port, {int backlog: 128});
 
   /**
    * Attach the HTTP server to an existing [:ServerSocket:]. If the
    * [HttpServer] is closed, the [HttpServer] will just detach itself,
    * and not close [serverSocket].
    */
   void listenOn(ServerSocket serverSocket);
 
   /**
    * Adds a request handler to the list of request handlers. The
@@ skipping 970 matching lines @@
 class RedirectLimitExceededException extends RedirectException {
   const RedirectLimitExceededException(List<RedirectInfo> redirects)
       : super("Redirect limit exceeded", redirects);
 }
 
 
 class RedirectLoopException extends RedirectException {
   const RedirectLoopException(List<RedirectInfo> redirects)
       : super("Redirect loop detected", redirects);
 }