Enable the mojo-based serial API in the renderer behind a flag.

extensions/extensions.gyp

 # Copyright 2013 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
@@ skipping 1023 matching lines @@
         'common/test_util.cc',
         'common/test_util.h',
         'common/value_builder.cc',
         'common/value_builder.h',
         'renderer/test_extensions_renderer_client.cc',
         'renderer/test_extensions_renderer_client.h',
         'test/extension_test_message_listener.cc',
         'test/extension_test_message_listener.h',
         'test/result_catcher.cc',
         'test/result_catcher.h',
+        'test/service_registration_manager_test_api.cc',
+        'test/service_registration_manager_test_api.h',
         'test/test_extensions_client.cc',
         'test/test_extensions_client.h',
         'test/test_permission_message_provider.cc',
         'test/test_permission_message_provider.h',
       ],
       # Disable c4267 warnings until we fix size_t to int truncations.
       'msvs_disabled_warnings': [ 4267, ],
     },
     {
       # The pak file generated by this target is intended to be shared by
@@ skipping 169 matching lines @@
       'conditions': [
         ['OS=="win" and win_use_allocator_shim==1', {
           'dependencies': [
             '../base/allocator/allocator.gyp:allocator',
           ],
         }],
       ],
     },
   ]
 }