Fix HttpResponse::writeCharCode.

sdk/lib/io/http_impl.dart

 // Copyright (c) 2013, 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.
 
 part of dart.io;
 
 const int _HEADERS_BUFFER_SIZE = 8 * 1024;
 
 class _HttpIncoming extends Stream<List<int>> {
   final int _transferLength;
@@ skipping 427 matching lines @@
       charset = "iso-8859-1";
     }
     return Encoding.getByName(charset);
   }
 
   void set encoding(Encoding value) {
     throw new StateError("IOSink encoding is not mutable");
   }
 
   void write(Object obj) {
+    if (!_headersWritten) _dataSink.encoding = encoding;
     _dataSink.write(obj);
   }
 
   void writeAll(Iterable objects, [String separator = ""]) {
+    if (!_headersWritten) _dataSink.encoding = encoding;
     _dataSink.writeAll(objects, separator);
   }
 
   void writeln([Object obj = ""]) {
+    if (!_headersWritten) _dataSink.encoding = encoding;
     _dataSink.writeln(obj);
   }
 
   void writeCharCode(int charCode) {
+    if (!_headersWritten) _dataSink.encoding = encoding;
     _dataSink.writeCharCode(charCode);
   }
 
   void add(List<int> data) {
     if (data.length == 0) return;
     _dataSink.add(data);
   }
 
   void addError(error, [StackTrace stackTrace]) {
     _dataSink.addError(error, stackTrace);
@@ skipping 2107 matching lines @@
 
 String _getHttpVersion() {
   var version = Platform.version;
   // Only include major and minor version numbers.
   int index = version.indexOf('.', version.indexOf('.') + 1);
   version = version.substring(0, index);
   return 'Dart/$version (dart:io)';
 }