Introduce SystemNetworkContextManager.

content/public/browser/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/ui.gni")
 
 # See //content/BUILD.gn for how this works.
 group("browser") {
   if (is_component_build) {
     public_deps = [
@@ skipping 149 matching lines @@
     "navigation_details.cc",
     "navigation_details.h",
     "navigation_entry.h",
     "navigation_handle.cc",
     "navigation_handle.h",
     "navigation_throttle.cc",
     "navigation_throttle.h",
     "navigation_type.h",
     "navigation_ui_data.h",
     "network_quality_observer_factory.h",
+    "network_service_instance.cc",
+    "network_service_instance.h",
     "notification_database_data.cc",
     "notification_database_data.h",
     "notification_details.h",
     "notification_event_dispatcher.h",
     "notification_observer.h",
     "notification_registrar.cc",
     "notification_registrar.h",
     "notification_service.h",
     "notification_source.h",
     "notification_types.h",
@@ skipping 174 matching lines @@
     ]
   }
 
   if (is_chromeos) {
     sources += [
       "arc_tracing_agent.cc",
       "arc_tracing_agent.h",
     ]
   }
 }