Add TRACE_EVENT macros to net.

net/http/http_server_properties_manager.cc

Index: net/http/http_server_properties_manager.cc
diff --git a/net/http/http_server_properties_manager.cc b/net/http/http_server_properties_manager.cc
index a592f441bb09eb71cb7371d421b33e5fb63f5600..02af675c0d62c7e905af4daef79467c1983cef5a 100644
--- a/net/http/http_server_properties_manager.cc
+++ b/net/http/http_server_properties_manager.cc
@@ -11,6 +11,7 @@
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
 #include "base/thread_task_runner_handle.h"
+#include "base/trace_event/trace_event.h"
 #include "base/values.h"
 #include "net/base/ip_address.h"
 #include "net/base/port_util.h"
@@ -822,6 +823,9 @@ void HttpServerPropertiesManager::UpdateCacheFromPrefsOnNetworkThread(
     ServerNetworkStatsMap* server_network_stats_map,
     QuicServerInfoMap* quic_server_info_map,
     bool detected_corrupted_prefs) {
+  TRACE_EVENT0(
+      "net",
+      "HttpServerPropertiesManager::UpdateCacheFromPrefsOnNetworkThread");
   // Preferences have the master data because admins might have pushed new
   // preferences. Update the cached data with new data from preferences.
   DCHECK(network_task_runner_->RunsTasksOnCurrentThread());