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

chrome/renderer/chrome_content_renderer_client.cc

 // Copyright (c) 2012 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 "chrome/renderer/chrome_content_renderer_client.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 71 matching lines @@
 #include "components/signin/core/common/profile_management_switches.h"
 #include "components/spellcheck/spellcheck_build_features.h"
 #include "components/startup_metric_utils/common/startup_metric.mojom.h"
 #include "components/subresource_filter/content/renderer/subresource_filter_agent.h"
 #include "components/subresource_filter/content/renderer/unverified_ruleset_dealer.h"
 #include "components/task_scheduler_util/renderer/initialization.h"
 #include "components/version_info/version_info.h"
 #include "components/visitedlink/renderer/visitedlink_slave.h"
 #include "components/web_cache/renderer/web_cache_impl.h"
 #include "content/public/common/content_constants.h"
+#include "content/public/common/content_features.h"
 #include "content/public/common/content_switches.h"
 #include "content/public/common/service_names.mojom.h"
 #include "content/public/common/url_constants.h"
 #include "content/public/renderer/plugin_instance_throttler.h"
 #include "content/public/renderer/render_frame.h"
 #include "content/public/renderer/render_frame_visitor.h"
 #include "content/public/renderer/render_thread.h"
 #include "content/public/renderer/render_view.h"
 #include "extensions/common/constants.h"
 #include "extensions/features/features.h"
@@ skipping 1499 matching lines @@
 
 std::unique_ptr<base::TaskScheduler::InitParams>
 ChromeContentRendererClient::GetTaskSchedulerInitParams() {
   return task_scheduler_util::
       GetRendererTaskSchedulerInitParamsFromCommandLine();
 }
 
 bool ChromeContentRendererClient::UsingSafeBrowsingMojoService() {
   if (safe_browsing_)
     return true;
-  if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kEnableNetworkService)) {
+  if (!base::FeatureList::IsEnabled(features::kNetworkService)) {

[Alexei Svitkine (slow), 2017/06/29 13:58:24]

Nit: No {}'s

[jam, 2017/06/30 17:21:18]

Done.

     return false;
   }
   RenderThread::Get()->GetConnector()->BindInterface(
       content::mojom::kBrowserServiceName, &safe_browsing_);
   return true;
 }