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

content/browser/utility_process_host_impl.cc

Index: content/browser/utility_process_host_impl.cc
diff --git a/content/browser/utility_process_host_impl.cc b/content/browser/utility_process_host_impl.cc
index b670a07c6a9e806332c5841d5c7c20a7a546dbcb..7aa297dbb7a900abe956e6909b19be5c68e8a6de 100644
--- a/content/browser/utility_process_host_impl.cc
+++ b/content/browser/utility_process_host_impl.cc
@@ -290,6 +290,7 @@ bool UtilityProcessHostImpl::StartProcess() {
 
     cmd_line->AppendSwitchASCII(switches::kProcessType,
                                 switches::kUtilityProcess);
+    BrowserChildProcessHostImpl::CopyFeatureAndFieldTrialFlags(cmd_line.get());
     std::string locale = GetContentClient()->browser()->GetApplicationLocale();
     cmd_line->AppendSwitchASCII(switches::kLang, locale);
 
@@ -302,7 +303,6 @@ bool UtilityProcessHostImpl::StartProcess() {
 
     // Browser command-line switches to propagate to the utility process.
     static const char* const kSwitchNames[] = {
-      switches::kEnableNetworkService,
       switches::kHostResolverRules,
       switches::kLogNetLog,
       switches::kNoSandbox,