[Extensions] Begin making Extension port initialization asynchronous

extensions/renderer/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/features.gni")
 
 assert(enable_extensions)
 
 # GYP version: extensions/extensions.gyp:extensions_renderer
 source_set("renderer") {
@@ skipping 33 matching lines @@
     "dom_activity_logger.h",
     "event_bindings.cc",
     "event_bindings.h",
     "extension_frame_helper.cc",
     "extension_frame_helper.h",
     "extension_groups.h",
     "extension_helper.cc",
     "extension_helper.h",
     "extension_injection_host.cc",
     "extension_injection_host.h",
+    "extension_port.cc",
+    "extension_port.h",
     "extensions_render_frame_observer.cc",
     "extensions_render_frame_observer.h",
     "extensions_renderer_client.cc",
     "extensions_renderer_client.h",
     "file_system_natives.cc",
     "file_system_natives.h",
     "gc_callback.cc",
     "gc_callback.h",
     "guest_view/extensions_guest_view_container.cc",
     "guest_view/extensions_guest_view_container.h",
@@ skipping 225 matching lines @@
     "//ui/base",
   ]
 
   if (enable_wifi_display && proprietary_codecs) {
     sources += [
       "api/display_source/wifi_display/wifi_display_elementary_stream_descriptor_unittest.cc",
       "api/display_source/wifi_display/wifi_display_media_packetizer_unittest.cc",
     ]
   }
 }