Standardize "net" category trace events

net/spdy/spdy_session_pool.cc

Index: net/spdy/spdy_session_pool.cc
diff --git a/net/spdy/spdy_session_pool.cc b/net/spdy/spdy_session_pool.cc
index 40c6615617faa8529c030fc12a7da1a930a8e641..dde05ada6438e6e23e49d40d5426760f05b416cf 100644
--- a/net/spdy/spdy_session_pool.cc
+++ b/net/spdy/spdy_session_pool.cc
@@ -18,6 +18,7 @@
 #include "net/log/net_log_event_type.h"
 #include "net/log/net_log_source.h"
 #include "net/log/net_log_with_source.h"
+#include "net/log/trace_constants.h"
 #include "net/spdy/spdy_session.h"
 
 namespace net {
@@ -81,7 +82,8 @@ base::WeakPtr<SpdySession> SpdySessionPool::CreateAvailableSessionFromSocket(
     std::unique_ptr<ClientSocketHandle> connection,
     const NetLogWithSource& net_log,
     bool is_secure) {
-  TRACE_EVENT0("net", "SpdySessionPool::CreateAvailableSessionFromSocket");
+  TRACE_EVENT0(kNetTracingCategory,
+               "SpdySessionPool::CreateAvailableSessionFromSocket");
 
   UMA_HISTOGRAM_ENUMERATION(
       "Net.SpdySessionGet", IMPORTED_FROM_SOCKET, SPDY_SESSION_GET_MAX);