Improve performance of proxy resolver by tracing DNS dependencies.

net/proxy/proxy_resolver_mac.h

 // 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.
 
 #ifndef NET_PROXY_PROXY_RESOLVER_MAC_H_
 #define NET_PROXY_PROXY_RESOLVER_MAC_H_
 
 #include "base/compiler_specific.h"
 #include "googleurl/src/gurl.h"
 #include "net/base/net_export.h"
@@ skipping 13 matching lines @@
   virtual int GetProxyForURL(const GURL& url,
                              ProxyInfo* results,
                              const net::CompletionCallback& callback,
                              RequestHandle* request,
                              const BoundNetLog& net_log) OVERRIDE;
 
   virtual void CancelRequest(RequestHandle request) OVERRIDE;
 
   virtual LoadState GetLoadState(RequestHandle request) const OVERRIDE;
 
-  virtual LoadState GetLoadStateThreadSafe(
-      RequestHandle request) const OVERRIDE;
-
   virtual void CancelSetPacScript() OVERRIDE;
 
   virtual int SetPacScript(
       const scoped_refptr<ProxyResolverScriptData>& script_data,
       const net::CompletionCallback& /*callback*/) OVERRIDE;
 
  private:
   scoped_refptr<ProxyResolverScriptData> script_data_;
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_PROXY_RESOLVER_MAC_H_