Restore missing debug flag supression from NSS update.

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 232552 (this should agree with "nss_rev" in DEPS).
@@ skipping 83 matching lines @@
       # Changed by Dart: '<(ssl_directory)/' added to all paths.
       'sources!': [
         '<(ssl_directory)/ssl/os2_err.c',
         '<(ssl_directory)/ssl/os2_err.h',
       ],
       'defines': [
         'NO_PKCS11_BYPASS',
         'NSS_ENABLE_ECC',
         'USE_UTIL_DIRECTLY',
       ],
+      'defines!': [
+        'DEBUG',
+      ],
       'dependencies': [
         # Changed by Dart.
         'zlib.gyp:zlib_dart',  # Added by Dart (the _dart postfix)
         # Dart: Start of copy of code from 'bodge' conditions section below.
         'nss.gyp:nspr_dart',  # Added by Dart (the _dart postfix)
         'nss.gyp:nss_dart',  # Added by Dart (the _dart postfix)
       ],
       'export_dependent_settings': [
         'nss.gyp:nspr_dart',  # Added by Dart (the _dart postfix)
         'nss.gyp:nss_dart',  # Added by Dart (the _dart postfix)
@@ skipping 90 matching lines @@
           'inherit_from': ['Dart_Base'],
           'defines': [
             'DEBUG',
           ],
         },
       },
     },
   ],
   }]],
 }