Add a feature flag for network service and about:flags entry for it.

content/renderer/render_frame_impl.cc

 // 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.
 
 #include "content/renderer/render_frame_impl.h"
 
 #include <algorithm>
 #include <map>
 #include <string>
 #include <utility>
@@ skipping 4326 matching lines @@
     // instance.
     RequestExtraData* current_request_data =
         static_cast<RequestExtraData*>(request.GetExtraData());
     if (current_request_data) {
       extra_data->set_navigation_initiated_by_renderer(
           current_request_data->navigation_initiated_by_renderer());
     }
   }
 
   // TODO: generalize how non-network schemes are sent to the renderer and used.
-  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kEnableNetworkService)) {
+  if (base::FeatureList::IsEnabled(features::kNetworkService)) {
     if (request.Url().ProtocolIs(url::kBlobScheme)) {
       extra_data->set_url_loader_factory_override(
           RenderThreadImpl::current()->GetBlobURLLoaderFactory());
     }
   }
 
   if (!extra_data->url_loader_factory_override())
     extra_data->set_url_loader_factory_override(url_loader_factory_.get());
 
   // TODO(kinuko, yzshen): We need to set up throttles for some worker cases
@@ skipping 2527 matching lines @@
       replaces_current_history_item(info.replaces_current_history_item),
       history_navigation_in_new_child_frame(
           info.is_history_navigation_in_new_child_frame),
       client_redirect(info.is_client_redirect),
       triggering_event_info(info.triggering_event_info),
       cache_disabled(info.is_cache_disabled),
       form(info.form),
       source_location(info.source_location) {}
 
 }  // namespace content