Add support for extensions_unittests to the GN build

chrome/chrome_tests.gypi

 # 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': {
     'chrome_browser_extensions_test_support_sources': [
       # A list of sources which is shared between different browser tests.
       'browser/apps/app_browsertest_util.cc',
       'browser/apps/app_browsertest_util.h',
       'browser/extensions/browsertest_util.cc',
@@ skipping 17 matching lines @@
       '../components/autofill/content/renderer/test_password_autofill_agent.cc',
       '../components/autofill/content/renderer/test_password_generation_agent.h',
       '../components/autofill/content/renderer/test_password_generation_agent.cc',
       # TODO(rockot): Remove this once extensions_browsertests exists.
       '../extensions/browser/api/app_window/app_window_apitest.cc',
       '../extensions/browser/api/bluetooth/bluetooth_apitest.cc',
       '../extensions/browser/api/bluetooth/bluetooth_private_apitest.cc',
       '../extensions/browser/api/bluetooth_low_energy/bluetooth_low_energy_apitest.cc',
       '../extensions/browser/api/bluetooth_socket/bluetooth_socket_apitest.cc',
       '../extensions/browser/api/cast_channel/cast_channel_apitest.cc',
-      '../extensions/browser/api/cast_channel/test_util.cc',
-      '../extensions/browser/api/cast_channel/test_util.h',
       '../extensions/browser/api/runtime/runtime_apitest.cc',
       '../extensions/browser/api/serial/serial_apitest.cc',
       '../extensions/browser/api/usb/usb_manual_apitest.cc',
       '../extensions/browser/app_window/app_window_browsertest.cc',
       '../extensions/browser/guest_view/extension_options/extension_options_apitest.cc',
       '../extensions/browser/guest_view/mime_handler_view/mime_handler_view_browsertest.cc',
       '../extensions/renderer/console_apitest.cc',
       '../extensions/renderer/script_context_browsertest.cc',
       'app/chrome_command_ids.h',
       'app/chrome_dll.rc',
@@ skipping 3179 matching lines @@
             ['enable_webrtc==1', {
               'dependencies': [
                 '../third_party/libjingle/libjingle.gyp:libjingle_webrtc'
               ]
             }],
           ],
         }]
     }],
   ],  # 'conditions'
 }