[Extensions] Begin making Extension port initialization asynchronous

extensions/extensions.gypi

 # Copyright 2015 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': {
     'extensions_common_constants_sources': [
       'common/constants.cc',
       'common/constants.h',
     ],
@@ skipping 892 matching lines @@
       'renderer/dispatcher.h',
       'renderer/dispatcher_delegate.h',
       'renderer/display_source_custom_bindings.cc',
       'renderer/display_source_custom_bindings.h',
       'renderer/document_custom_bindings.cc',
       'renderer/document_custom_bindings.h',
       'renderer/dom_activity_logger.cc',
       'renderer/dom_activity_logger.h',
       'renderer/event_bindings.cc',
       'renderer/event_bindings.h',
+      'renderer/extension_port.cc',
+      'renderer/extension_port.h',
       'renderer/extension_frame_helper.cc',
       'renderer/extension_frame_helper.h',
       'renderer/extension_groups.h',
       'renderer/extension_helper.cc',
       'renderer/extension_helper.h',
       'renderer/extension_injection_host.cc',
       'renderer/extension_injection_host.h',
       'renderer/extensions_render_frame_observer.cc',
       'renderer/extensions_render_frame_observer.h',
       'renderer/extensions_renderer_client.cc',
@@ skipping 215 matching lines @@
       'test/result_catcher.h',
       'test/test_content_utility_client.cc',
       'test/test_content_utility_client.h',
       'test/test_extensions_client.cc',
       'test/test_extensions_client.h',
       'test/test_permission_message_provider.cc',
       'test/test_permission_message_provider.h',
     ],
   },
 }