Improve performance of proxy resolver by tracing DNS dependencies.

net/proxy/proxy_resolver_mac.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/proxy/proxy_resolver_mac.h"
 
 #include <CoreFoundation/CoreFoundation.h>
 
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
@@ skipping 178 matching lines @@
 
 void ProxyResolverMac::CancelRequest(RequestHandle request) {
   NOTREACHED();
 }
 
 LoadState ProxyResolverMac::GetLoadState(RequestHandle request) const {
   NOTREACHED();
   return LOAD_STATE_IDLE;
 }
 
-LoadState ProxyResolverMac::GetLoadStateThreadSafe(
-    RequestHandle request) const {
-  return LOAD_STATE_IDLE;
-}
-
 void ProxyResolverMac::CancelSetPacScript() {
   NOTREACHED();
 }
 
 int ProxyResolverMac::SetPacScript(
     const scoped_refptr<ProxyResolverScriptData>& script_data,
     const CompletionCallback& /*callback*/) {
   script_data_ = script_data;
   return OK;
 }
 
 }  // namespace net