Fix empty zlib deflate and early close of responses.

sdk/lib/io/data_transformer.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;
 
 /**
  * Private helper-class to handle native filters.
  */
 abstract class _Filter {
@@ skipping 18 matching lines @@
   void end();
 
   external static _Filter newZLibDeflateFilter(bool gzip, int level);
   external static _Filter newZLibInflateFilter();
 }
 
 
 class _FilterTransformer extends StreamEventTransformer<List<int>, List<int>> {
   final _Filter _filter;
   bool _closed = false;
+  bool _empty = true;
 
   _FilterTransformer(_Filter this._filter);
 
   void handleData(List<int> data, EventSink<List<int>> sink) {
     if (_closed) return;
     try {
+      _empty = false;
       _filter.process(data);
       var out;
       while ((out = _filter.processed(flush: false)) != null) {
         sink.add(out);
       }
     } catch (e, s) {
       _closed = true;
       sink.addError(new AsyncError(e, s));
       sink.close();
     }
   }
 
   void handleDone(EventSink<List<int>> sink) {
     if (_closed) return;
+    if (_empty) _filter.process(const []);
     try {
       var out;
       while ((out = _filter.processed()) != null) {
         sink.add(out);
       }
     } catch (e, s) {
       sink.addError(new AsyncError(e, s));
       _closed = true;
     }
     if (!_closed) _filter.end();
+    _closed = true;
     sink.close();
   }
 }
 
 
 /**
  * ZLibDeflater class used to deflate a stream of bytes, using zlib.
  */
 class ZLibDeflater extends _FilterTransformer {
   ZLibDeflater({bool gzip: true, int level: 6})
       : super(_Filter.newZLibDeflateFilter(gzip, level));
 }
 
 
 /**
  * ZLibInflater class used to inflate a stream of bytes, using zlib.
  */
 class ZLibInflater extends _FilterTransformer {
   ZLibInflater() : super(_Filter.newZLibInflateFilter());
 }