Standardize "net" category trace events

net/socket/transport_client_socket_pool.cc

Index: net/socket/transport_client_socket_pool.cc
diff --git a/net/socket/transport_client_socket_pool.cc b/net/socket/transport_client_socket_pool.cc
index 9df352aacfaf092827cfee07bfdb58255f85fbb8..3cbbd611732fd9d6d0d91a9db28d5f9d0345237e 100644
--- a/net/socket/transport_client_socket_pool.cc
+++ b/net/socket/transport_client_socket_pool.cc
@@ -19,6 +19,7 @@
 #include "base/values.h"
 #include "net/base/ip_endpoint.h"
 #include "net/base/net_errors.h"
+#include "net/base/trace_constants.h"
 #include "net/log/net_log.h"
 #include "net/log/net_log_event_type.h"
 #include "net/log/net_log_source_type.h"
@@ -268,7 +269,8 @@ int TransportConnectJob::DoResolveHost() {
 }
 
 int TransportConnectJob::DoResolveHostComplete(int result) {
-  TRACE_EVENT0("net", "TransportConnectJob::DoResolveHostComplete");
+  TRACE_EVENT0(kNetTracingCategory,
+               "TransportConnectJob::DoResolveHostComplete");
   connect_timing_.dns_end = base::TimeTicks::Now();
   // Overwrite connection start time, since for connections that do not go
   // through proxies, |connect_start| should not include dns lookup time.