Add HTTP handler registration to the HTTP server

tests/standalone/src/io/HttpTest.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.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
 #import("dart:isolate");
@@ skipping 168 matching lines @@
     _requestHandlers["/expires2"] =
         (HttpRequest request, HttpResponse response) {
           _expires2Handler(request, response);
         };
 
     this.port.receive((var message, SendPort replyTo) {
       if (message.isStart) {
         _server = new HttpServer();
         try {
           _server.listen("127.0.0.1", 0);
-          _server.onRequest = (HttpRequest req, HttpResponse rsp) {
+          _server.defaultRequestHandler = (HttpRequest req, HttpResponse rsp) {
             _requestReceivedHandler(req, rsp);
           };
           replyTo.send(new TestServerStatus.started(_server.port), null);
         } catch (var e) {
           replyTo.send(new TestServerStatus.error(), null);
         }
       } else if (message.isStop) {
         _server.close();
         this.port.close();
         replyTo.send(new TestServerStatus.stopped(), null);
@@ skipping 308 matching lines @@
     HttpClientConnection conn2 = httpClient.get("127.0.0.1", port, "/expires2");
     conn2.onResponse = (HttpClientResponse response) {
       processResponse(response);
     };
   });
   testServerMain.start();
 }
 
 
 void main() {
-  //testStartStop();
+  testStartStop();
   testGET();
   testPOST(true);
   testPOST(false);
   testReadInto(true);
   testReadInto(false);
   testReadShort(true);
   testReadShort(false);
   test404();
   testReasonPhrase();
   testHost();
   testExpires();
 }