Add support for extensions_unittests to the GN build

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 1124 matching lines @@
       'dependencies': [
         '../base/base.gyp:base',
         '../base/base.gyp:base_prefs_test_support',
         '../components/components.gyp:user_prefs',
         '../content/content.gyp:content_browser',
         '../content/content.gyp:content_common',
         '../content/content_shell_and_tests.gyp:test_support_content',
         '../net/net.gyp:net_test_support',
         '../testing/gtest.gyp:gtest',
         'browser/api/api_registration.gyp:extensions_api_registration',
+        'common/api/api.gyp:cast_channel_proto',
         'common/api/api.gyp:extensions_api',
         'extensions_browser',
         'extensions_common',
         'extensions_resources.gyp:extensions_resources',
       ],
       'include_dirs': [
         '..',
         '<(SHARED_INTERMEDIATE_DIR)',
       ],
       'sources': [
         # Note: sources list duplicated in GN build.
+        'browser/api/cast_channel/test_util.cc',
+        'browser/api/cast_channel/test_util.h',
         'browser/api/dns/mock_host_resolver_creator.cc',
         'browser/api/dns/mock_host_resolver_creator.h',
         'browser/api/storage/settings_test_util.cc',
         'browser/api/storage/settings_test_util.h',
         'browser/api_test_utils.cc',
         'browser/api_test_utils.h',
         'browser/api_unittest.cc',
         'browser/api_unittest.h',
         'browser/app_window/test_app_window_contents.cc',
         'browser/app_window/test_app_window_contents.h',
@@ skipping 77 matching lines @@
               '<(SHARED_INTERMEDIATE_DIR)/blink/devtools_resources.pak',
             ],
             'pak_output': '<(PRODUCT_DIR)/extensions_shell_and_test.pak',
           },
           'includes': [ '../build/repack_action.gypi' ],
         },
       ],
     },
   ]
 }