Make hashCode a getter and not a method.

tests/standalone/io/http_server_socket_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.
 
 #import("dart:io");
 #import("dart:isolate");
 #import("dart:math");
 
 class ExpectedDataOutputStream implements OutputStream {
   ExpectedDataOutputStream(List<int> this._data,
@@ skipping 91 matching lines @@
   void set onClosed(void callback()) {
     _onClosed = callback;
   }
 
   void set onError(void callback(e)) {
     _onError = callback;
   }
 
   OutputStream get outputStream => _outputStream;
 
-  int hashCode() => _hashCode;
+  int get hashCode => _hashCode;
 
   List<int> _read;
   bool _closed = false;
   int _hashCode;
   Function _onData;
   Function _onClosed;
   Function _onError;
   Function _onClosedInternal;
   List<int> _data;
   ExpectedDataOutputStream _outputStream;
@@ skipping 89 matching lines @@
       "GET / HTTP/1.1\r\nKeep-Alive: False\r\n\r\n",
       "HTTP/1.1 200 OK\r\ntransfer-encoding: chunked\r\nconnection: close"
       "\r\n\r\n0\r\n\r\n");
 
   server.close();
 }
 
 void main() {
   testSocketClose();
 }