Introduce (private) ZLibFilter to dart:io.

runtime/bin/filter_impl.dart

Index: runtime/bin/filter_impl.dart
diff --git a/runtime/bin/filter_impl.dart b/runtime/bin/filter_impl.dart
new file mode 100644
index 0000000000000000000000000000000000000000..23fff453f31f2bae69453a2145f67426afe3d775
--- /dev/null
+++ b/runtime/bin/filter_impl.dart
@@ -0,0 +1,24 @@
+// 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.
+
+
+class _FilterImpl extends NativeFieldWrapperClass1 implements _Filter {
+  _FilterImpl() {
+    _init();
+  }
+
+  void process(List<int> data) native "Filter_Process";
+
+  List<int> processed([bool flush = false]) native "Filter_Processed";
+
+  void end() native "Filter_End";
+}
+
+class _GZipDeflateFilterImpl extends _FilterImpl {
+  void _init() native "Filter_CreateGZipDeflate";
+}
+
+class _ZLibInflateFilterImpl extends _FilterImpl {
+  void _init() native "Filter_CreateZLibInflate";
+}