Disable NSS build targets in a Dartium build.

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 165464 (this should agree with "nss_rev" in DEPS).
@@ skipping 11 matching lines @@
         # Because we have a patched zlib, we cannot use the system libz.
         # TODO(pvalchev): OpenBSD is purposefully left out, as the system
         # zlib brings up an incompatibility that breaks rendering.
         'use_system_zlib%': 1,
       }, {
         'use_system_zlib%': 0,
       }],
     ],
     'use_system_minizip%': 0,
   },
+  # Added by Dart.  We do not indent, so diffs with the original are clearer.
+  'conditions': [[ 'in_dartium==0', {
   'targets': [
     {
       'target_name': 'zlib_dart',
       'type': 'static_library',
       'conditions': [
         ['use_system_zlib==0', {
           # Changed by Dart: '<(zlib_directory)/' added to all paths.
           'sources': [
             '<(zlib_path)/adler32.c',
             '<(zlib_path)/compress.c',
@@ skipping 115 matching lines @@
               '-Wno-parentheses-equality',
             ],
           },
           'cflags': [
             '-Wno-parentheses-equality',
           ],
         }],
       ],
     }
   ],
+  }]],
 }