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 6693 matching lines @@
   if (GetContentClient()->renderer()->ShouldOverridePageVisibilityState(
           this, &override_state))
     return override_state;
   return current_state;
 }
 
 std::unique_ptr<blink::WebURLLoader> RenderFrameImpl::CreateURLLoader(
     const blink::WebURLRequest& request,
     base::SingleThreadTaskRunner* task_runner) {
   ChildThreadImpl* child_thread = ChildThreadImpl::current();
-  const bool network_service_enabled =
-      base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kEnableNetworkService);
-  if (network_service_enabled && child_thread) {
+  if (base::FeatureList::IsEnabled(features::kNetworkService) && child_thread) {
     // Use if per-frame or per-scheme URLLoaderFactory is given.
     mojom::URLLoaderFactory* factory = url_loader_factory_.get();
 
     if (request.Url().ProtocolIs(url::kBlobScheme))
       factory = RenderThreadImpl::current()->GetBlobURLLoaderFactory();
 
     if (factory) {
       return base::MakeUnique<WebURLLoaderImpl>(
           child_thread->resource_dispatcher(), task_runner, factory);
     }
@@ skipping 175 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