Update NSS to 3.16.4. Updated to Chromium's copy of NSS at revision 291806

dart/runtime/bin/net/zlib.gyp

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # 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.
 
 # This file is a modified copy of src/third_party/zlib/zlib.gyp from Chromium.
-# Revision 257452 (this should agree with "nss_rev" in DEPS).
+# Revision 291806 (this should agree with "nss_rev" in DEPS).
 {
   # Added by Dart. All Dart comments refer to the following block or line.
   'includes': [
     '../../tools/gyp/runtime-configurations.gypi',
     '../../tools/gyp/nss_configurations.gypi',
   ],
   'variables': {
     # Added by Dart.
     'zlib_path': '../../../third_party/zlib',
   },
@@ skipping 45 matching lines @@
       },
       'conditions': [
         ['OS!="win"', {
           'product_name': 'chrome_zlib',
         }],
       ],
     },
   ],
   }]],
 }