Use patching for dart:io.

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 98 matching lines @@
 
   /**
    * Sets the error handler that is called when a connection error occurs.
    */
   void set onError(void callback(e));
 
   /**
    * Set the timeout, in seconds, for sessions of this HTTP server. Default
    * is 20 minutes.
    */
-  int set sessionTimeout(int timeout);
+  set sessionTimeout(int timeout);
 }
 
 
 /**
  * Access to the HTTP headers for requests and responses. In some
  * situations the headers will be imutable and the mutating methods
  * will then throw exceptions.
  *
  * For all operation on HTTP headers the header name is
  * case-insensitive.
@@ skipping 266 matching lines @@
 
 abstract class HttpSession {
   /**
    * Get the id for the current session.
    */
   String get id;
 
   /**
    * Access the user-data associated with the session.
    */
-  Dynamic data;
+  dynamic data;
 
   /**
    * Destroy the session. This will terminate the session and any further
    * connections with this id will be given a new id and session.
    */
   void destroy();
 
   /**
    * Set a callback that will be called when the session is timed out.
    */
@@ skipping 633 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);
 }