Add a new attachTo method to HttpServer, for using an existing ServerSocket.

tests/standalone/src/io/HttpServerTest.dart

Index: tests/standalone/src/io/HttpServerTest.dart
===================================================================
--- tests/standalone/src/io/HttpServerTest.dart	(revision 0)
+++ tests/standalone/src/io/HttpServerTest.dart	(revision 0)
@@ -0,0 +1,64 @@
+// 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.
+
+#import("dart:io");
+#import("dart:isolate");
+
+void testListenOn() {
+  ServerSocket socket = new ServerSocket("127.0.0.1", 0, 5);
+
+  socket.onError = (Exception e) {
+    Expect.fail("ServerSocket closed unexpected");
+  };
+
+  void test(void onDone()) {
+    HttpServer server = new HttpServer();
+    Expect.throws(() => server.port);
+
+    ReceivePort serverPort = new ReceivePort();
+    server.onRequest = (HttpRequest request, HttpResponse response) {
+      request.inputStream.onClosed = () {
+        response.outputStream.close();
+        server.close();
+        Expect.throws(() => server.port);
+        serverPort.close();
+        onDone();
+      };
+    };
+
+    server.onError = (Exception e) {
+      Expect.fail("Unexpected error in Http Server: $e");
+    };
+
+    server.listenOn(socket);
+    Expect.equals(socket.port, server.port);
+
+    HttpClient client = new HttpClient();
+    HttpClientConnection conn = client.get("127.0.0.1", socket.port, "/");
+    conn.onRequest = (HttpClientRequest request) {
+      request.outputStream.close();
+    };
+    ReceivePort clientPort = new ReceivePort();
+    conn.onResponse = (HttpClientResponse response) {
+      response.inputStream.onClosed = () {
+        client.shutdown();
+        clientPort.close();
+      };
+    };
+    conn.onError = (Exception e) {
+      Expect.fail("Unexpected error in Http Client");
+    };
+  };
+
+  // Test two connection after each other.
+  test(() {
+    test(() {
+      socket.close();
+    });
+  });
+}
+
+void main() {
+  testListenOn();
+}