Add flush to HTTP output streams

tests/standalone/io/http_advanced_test.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 160 matching lines @@
     response.cookies.add(cookie2);
     response.outputStream.close();
   }
 
   void _cookie2Handler(HttpRequest request, HttpResponse response) {
     // Two cookies passed with this request.
     Expect.equals(2, request.cookies.length);
     response.outputStream.close();
   }
 
+  void _flushHandler(HttpRequest request, HttpResponse response) {
+    response.outputStream.flush();
+    response.outputStream.close();
+  }
+
   void init() {
     // Setup request handlers.
     _requestHandlers = new Map();
     _requestHandlers["/host"] =
         (HttpRequest request, HttpResponse response) {
           _hostHandler(request, response);
         };
     _requestHandlers["/expires1"] =
         (HttpRequest request, HttpResponse response) {
           _expires1Handler(request, response);
@@ skipping 11 matching lines @@
           _contentType2Handler(request, response);
         };
     _requestHandlers["/cookie1"] =
         (HttpRequest request, HttpResponse response) {
           _cookie1Handler(request, response);
         };
     _requestHandlers["/cookie2"] =
         (HttpRequest request, HttpResponse response) {
           _cookie2Handler(request, response);
         };
+    _requestHandlers["/flush"] =
+        (HttpRequest request, HttpResponse response) {
+          _flushHandler(request, response);
+        };
   }
 
   void dispatch(message, replyTo) {
     if (message.isStart) {
       _server = new HttpServer();
       try {
         _server.listen("127.0.0.1", 0);
         _server.defaultRequestHandler = (HttpRequest req, HttpResponse rsp) {
           _requestReceivedHandler(req, rsp);
         };
@@ skipping 176 matching lines @@
       };
       conn2.onResponse = (HttpClientResponse ignored) {
         httpClient.shutdown();
         testServerMain.shutdown();
       };
     };
   });
   testServerMain.start();
 }
 
+void testFlush() {
+  TestServerMain testServerMain = new TestServerMain();
+  testServerMain.setServerStartedHandler((int port) {
+    HttpClient httpClient = new HttpClient();
+
+    HttpClientConnection conn = httpClient.get("127.0.0.1", port, "/flush");
+    conn.onRequest = (HttpClientRequest request) {
+      request.outputStream.flush();
+      request.outputStream.close();
+    };
+    conn.onResponse = (HttpClientResponse response) {
+      Expect.equals(HttpStatus.OK, response.statusCode);
+      httpClient.shutdown();
+      testServerMain.shutdown();
+    };
+  });
+  testServerMain.start();
+}
+
 void main() {
   testHost();
   testExpires();
   testContentType();
   testCookies();
+  testFlush();
 }