Actually end a ZLib stream with a Z_FINISH marker.

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 {
   /**
    * Call to process a chunk of data. A call to [process] should only be made
    * when [processed] returns [null].
    */
   void process(List<int> data);
 
   /**
    * Get a chunk of processed data. When there are no more data available,
    * [processed] will return [null]. Set [flush] to [false] for non-final
    * calls to improve performance of some filters.
+   *
+   * The last call to [processed] should have [end] set to [true]. This will make
+   * sure a 'end' packet is written on the stream.
    */
-  List<int> processed({bool flush: true});
+  List<int> processed({bool flush: true, bool end: false});
 
   /**
    * Mark the filter as closed. Always call this method for any filter created
    * to avoid leaking resources. [end] can be called at any time, but any
    * successive calls to [process] or [processed] will fail.
    */
   void end();
 
   external static _Filter newZLibDeflateFilter(bool gzip, int level);
   external static _Filter newZLibInflateFilter();
@@ skipping 22 matching lines @@
       sink.addError(e);
       sink.close();
     }
   }
 
   void handleDone(EventSink<List<int>> sink) {
     if (_closed) return;
     if (_empty) _filter.process(const []);
     try {
       var out;
-      while ((out = _filter.processed()) != null) {
+      while ((out = _filter.processed(end: true)) != null) {
         sink.add(out);
       }
     } catch (e, s) {
       // TODO(floitsch): we are losing the stack trace.
       sink.addError(e);
       _closed = true;
     }
     if (!_closed) _filter.end();
     _closed = true;
     sink.close();
@@ skipping 10 matching lines @@
 }
 
 
 /**
  * ZLibInflater class used to inflate a stream of bytes, using zlib.
  */
 class ZLibInflater extends _FilterTransformer {
   ZLibInflater() : super(_Filter.newZLibInflateFilter());
 }