[Not for review] Add TRACE_EVENTs and chrome://flags for preconnect

net/dns/dns_response.cc

Index: net/dns/dns_response.cc
diff --git a/net/dns/dns_response.cc b/net/dns/dns_response.cc
index 5d234244a09ed7448bf89ec874d881f1b1e69c1f..0c6382db4c8130286cc47f43554ffcb4520bf63d 100644
--- a/net/dns/dns_response.cc
+++ b/net/dns/dns_response.cc
@@ -9,6 +9,7 @@
 #include "base/big_endian.h"
 #include "base/strings/string_util.h"
 #include "base/sys_byteorder.h"
+#include "base/trace_event/trace_event.h"
 #include "net/base/address_list.h"
 #include "net/base/io_buffer.h"
 #include "net/base/ip_address.h"
@@ -278,6 +279,7 @@ const dns_protocol::Header* DnsResponse::header() const {
 DnsResponse::Result DnsResponse::ParseToAddressList(
     AddressList* addr_list,
     base::TimeDelta* ttl) const {
+  TRACE_EVENT0("net", "DnsResponse::ParseToAddressList");
   DCHECK(IsValid());
   // DnsTransaction already verified that |response| matches the issued query.
   // We still need to determine if there is a valid chain of CNAMEs from the