Introduce (private) ZLibFilter to dart:io.

runtime/bin/bin.gypi

 # 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.
 
 {
   'variables': {
     'crypto_cc_file': '<(SHARED_INTERMEDIATE_DIR)/crypto_gen.cc',
     'io_cc_file': '<(SHARED_INTERMEDIATE_DIR)/io_gen.cc',
     'json_cc_file': '<(SHARED_INTERMEDIATE_DIR)/json_gen.cc',
     'uri_cc_file': '<(SHARED_INTERMEDIATE_DIR)/uri_gen.cc',
@@ skipping 207 matching lines @@
     {
       'target_name': 'libdart_builtin',
       'type': 'static_library',
       'dependencies': [
         'generate_builtin_cc_file',
         'generate_crypto_cc_file',
         'generate_io_cc_file',
         'generate_json_cc_file',
         'generate_uri_cc_file',
         'generate_utf_cc_file',
+        'libzlib',
       ],
       'include_dirs': [
         '..',
       ],
       'sources': [
         'builtin_natives.cc',
         'builtin.h',
       ],
       'includes': [
         'builtin_impl_sources.gypi',
@@ skipping 281 matching lines @@
         ['OS=="mac"', {
           'xcode_settings': {
             'OTHER_LDFLAGS': [ '-undefined', 'dynamic_lookup' ],
           },
         }],
       ],
     },
   ],
 }