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

chrome/renderer/chrome_content_renderer_client.cc

Index: chrome/renderer/chrome_content_renderer_client.cc
diff --git a/chrome/renderer/chrome_content_renderer_client.cc b/chrome/renderer/chrome_content_renderer_client.cc
index fa44f43c2856ea1a3dafe15368be605bfb5da430..25472056c719448c5e79647d39d21ec113ec56df 100644
--- a/chrome/renderer/chrome_content_renderer_client.cc
+++ b/chrome/renderer/chrome_content_renderer_client.cc
@@ -89,6 +89,7 @@
 #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"
@@ -1608,8 +1609,7 @@ ChromeContentRendererClient::GetTaskSchedulerInitParams() {
 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(