Add support for building "ios_chrome_unittests" with gn.

ios/ios_tests.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/public/test
       'target_name': 'test_support_ios',
       'type': 'static_library',
       'sources': [
         # TODO(droger): Move most of these files to
         # //ios/chrome/ios_chrome_tests.gyp, see http://crbug.com/437333
         'public/test/fake_string_provider.cc',
         'public/test/fake_string_provider.h',
         'public/test/fake_sync_service_factory.cc',
         'public/test/fake_sync_service_factory.h',
         'public/test/test_chrome_browser_provider.h',
@@ skipping 13 matching lines @@
         '../sync/sync.gyp:sync',
         '../testing/gtest.gyp:gtest',
         'provider/ios_provider_chrome.gyp:ios_provider_chrome_browser',
       ],
       'include_dirs': [
         '..',
       ],
     },
   ],
 }