[iOS][GN] Port ios_net_unittests to build with gn.

ios/net/ios_net_unittests.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': [
     {
+      # GN version: //ios/net:ios_net_unittests
       'target_name': 'ios_net_unittests',
       'type': '<(gtest_target_type)',
       'dependencies': [
         '../../base/base.gyp:base',
         '../../base/base.gyp:run_all_unittests',
         '../../net/net.gyp:net_test_support',
         '../../testing/gtest.gyp:gtest',
         '../../url/url.gyp:url_lib',
         'ios_net.gyp:ios_net',
       ],
       'include_dirs': [
         '../..',
       ],
       'sources': [
         'clients/crn_forwarding_network_client_factory_unittest.mm',
         'cookies/cookie_cache_unittest.cc',
         'cookies/cookie_creation_time_manager_unittest.mm',
         'cookies/cookie_store_ios_unittest.mm',
         'cookies/system_cookie_util_unittest.mm',
         'http_response_headers_util_unittest.mm',
         'nsurlrequest_util_unittest.mm',
         'protocol_handler_util_unittest.mm',
         'url_scheme_util_unittest.mm',
       ],
     },
   ],
 }