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

dart/runtime/bin/net/ssl.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 Chromium's src/net/third_party/nss/ssl.gyp.
-# Revision 257452 (this should agree with "nss_rev" in DEPS).
+# Revision 291806 (this should agree with "nss_rev" in DEPS).
 
 # The following modification was made to make sure we have the same
 # xcode_settings on all configurations (otherwise we can't build with ninja):
 #   'configurations': {
 #     'Debug_Base': {
 # +     'inherit_from': ['Dart_Base'],
 #       'defines': [
 #         'DEBUG',
 #       ],
 #    },
@@ skipping 186 matching lines @@
           'inherit_from': ['Dart_Base'],
           'defines': [
             'DEBUG',
           ],
         },
       },
     },
   ],
   }]],
 }