Standardize "net" category trace events

net/socket/socket_posix.cc

Index: net/socket/socket_posix.cc
diff --git a/net/socket/socket_posix.cc b/net/socket/socket_posix.cc
index a86bf855b3230fb3166efb847bbdfd58da18fcac..09d9baec87e0139e41226b8a1b8b5a8de5c6a6c6 100644
--- a/net/socket/socket_posix.cc
+++ b/net/socket/socket_posix.cc
@@ -19,6 +19,7 @@
 #include "net/base/ip_endpoint.h"
 #include "net/base/net_errors.h"
 #include "net/base/sockaddr_storage.h"
+#include "net/base/trace_constants.h"
 
 namespace net {
 
@@ -369,7 +370,8 @@ void SocketPosix::DetachFromThread() {
 }
 
 void SocketPosix::OnFileCanReadWithoutBlocking(int fd) {
-  TRACE_EVENT0("net", "SocketPosix::OnFileCanReadWithoutBlocking");
+  TRACE_EVENT0(kNetTracingCategory,
+               "SocketPosix::OnFileCanReadWithoutBlocking");
   DCHECK(!accept_callback_.is_null() || !read_callback_.is_null());
   if (!accept_callback_.is_null()) {
     AcceptCompleted();