Add chrome test support target to GN build.

components/search_engines.gypi

 # Copyright 2014 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.
 
 {
   'targets': [
     {
       # GN version: //components/search_engines
       'target_name': 'search_engines',
       'type': 'static_library',
@@ skipping 63 matching lines @@
             'policy'
            ],
            'sources!': [
              'search_engines/default_search_policy_handler.cc',
              'search_engines/default_search_policy_handler.h',
            ],
         }],
       ],
     },
     {
+      # GN version: //components/search_engines:test_support
       'target_name': 'search_engines_test_support',
       'type': 'static_library',
       'dependencies': [
         '../testing/gtest.gyp:gtest',
         'search_engines',
       ],
       'include_dirs': [
         '..',
       ],
       'sources': [
         'search_engines/default_search_pref_test_util.cc',
         'search_engines/default_search_pref_test_util.h',
         'search_engines/testing_search_terms_data.cc',
         'search_engines/testing_search_terms_data.h',
       ],
     },
   ],
 }