Improve performance of proxy resolver by tracing DNS dependencies.

net/proxy/proxy_resolver_winhttp.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_WINHTTP_H_
 #define NET_PROXY_PROXY_RESOLVER_WINHTTP_H_
 
 #include "base/compiler_specific.h"
 #include "googleurl/src/gurl.h"
 #include "net/proxy/proxy_resolver.h"
@@ skipping 12 matching lines @@
   // ProxyResolver implementation:
   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:
   bool OpenWinHttpSession();
   void CloseWinHttpSession();
 
   // Proxy configuration is cached on the session handle.
   HINTERNET session_handle_;
 
   GURL pac_url_;
 
   DISALLOW_COPY_AND_ASSIGN(ProxyResolverWinHttp);
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_PROXY_RESOLVER_WINHTTP_H_