Standardize "net" category trace events

net/proxy/proxy_resolver_v8_tracing.cc

Index: net/proxy/proxy_resolver_v8_tracing.cc
diff --git a/net/proxy/proxy_resolver_v8_tracing.cc b/net/proxy/proxy_resolver_v8_tracing.cc
index 57cbfb04ebc5ff9a0a07bc22e4f8a4423d003afd..0849ddcf31b38000dda0ef06bcc3cd4a8187f4c6 100644
--- a/net/proxy/proxy_resolver_v8_tracing.cc
+++ b/net/proxy/proxy_resolver_v8_tracing.cc
@@ -25,6 +25,7 @@
 #include "net/base/network_interfaces.h"
 #include "net/dns/host_resolver.h"
 #include "net/log/net_log_with_source.h"
+#include "net/log/trace_constants.h"
 #include "net/proxy/proxy_info.h"
 #include "net/proxy/proxy_resolver_error_observer.h"
 #include "net/proxy/proxy_resolver_v8.h"
@@ -562,7 +563,7 @@ void Job::ExecuteNonBlocking() {
 }
 
 int Job::ExecuteProxyResolver() {
-  TRACE_EVENT0("net", "Job::ExecuteProxyResolver");
+  TRACE_EVENT0(kNetTracingCategory, "Job::ExecuteProxyResolver");
   int result = ERR_UNEXPECTED;  // Initialized to silence warnings.
 
   switch (operation_) {