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

content/browser/loader/navigation_url_loader.cc

 // 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.
 
 #include "content/browser/loader/navigation_url_loader.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/memory/ptr_util.h"
 #include "content/browser/frame_host/navigation_request_info.h"
 #include "content/browser/loader/navigation_url_loader_factory.h"
 #include "content/browser/loader/navigation_url_loader_impl.h"
 #include "content/browser/loader/navigation_url_loader_network_service.h"
 #include "content/public/browser/navigation_ui_data.h"
-#include "content/public/common/content_switches.h"
+#include "content/public/common/content_features.h"
 
 namespace content {
 
 static NavigationURLLoaderFactory* g_factory = nullptr;
 
 std::unique_ptr<NavigationURLLoader> NavigationURLLoader::Create(
     ResourceContext* resource_context,
     StoragePartition* storage_partition,
     std::unique_ptr<NavigationRequestInfo> request_info,
     std::unique_ptr<NavigationUIData> navigation_ui_data,
     ServiceWorkerNavigationHandle* service_worker_handle,
     AppCacheNavigationHandle* appcache_handle,
     NavigationURLLoaderDelegate* delegate) {
   if (g_factory) {
     return g_factory->CreateLoader(
         resource_context, storage_partition, std::move(request_info),
         std::move(navigation_ui_data), service_worker_handle, delegate);
   }
-  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kEnableNetworkService)) {
+  if (base::FeatureList::IsEnabled(features::kNetworkService)) {
     return base::MakeUnique<NavigationURLLoaderNetworkService>(
         resource_context, storage_partition, std::move(request_info),
         std::move(navigation_ui_data), service_worker_handle, appcache_handle,
         delegate);
   } else {
     return base::MakeUnique<NavigationURLLoaderImpl>(
         resource_context, storage_partition, std::move(request_info),
         std::move(navigation_ui_data), service_worker_handle, appcache_handle,
         delegate);
   }
 }
 
 void NavigationURLLoader::SetFactoryForTesting(
     NavigationURLLoaderFactory* factory) {
   DCHECK(g_factory == nullptr || factory == nullptr);
   g_factory = factory;
 }
 
 }  // namespace content