Introduce experimental natives that are enabled by a runtime flag.

src/extensions/experimental/experimental.gyp

 # Copyright 2011 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 57 matching lines @@
       },
       'actions': [
         {
           'action_name': 'js2c_i18n',
           'inputs': [
             '../../../tools/js2c.py',
             '<@(library_files)',
           ],
           'outputs': [
             '<(SHARED_INTERMEDIATE_DIR)/i18n-js.cc',
-            '<(SHARED_INTERMEDIATE_DIR)/i18n-js-empty.cc'
           ],
           'action': [
             'python',
             '../../../tools/js2c.py',
             '<@(_outputs)',
             'I18N',
             '<@(library_files)'
           ],
         },
       ],
     },
   ],  # targets
 }