Improve performance of proxy resolver by tracing DNS dependencies.

net/proxy/proxy_resolver.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_H_
 #define NET_PROXY_PROXY_RESOLVER_H_
 
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/string16.h"
@@ skipping 34 matching lines @@
                              const net::CompletionCallback& callback,
                              RequestHandle* request,
                              const BoundNetLog& net_log) = 0;
 
   // Cancels |request|.
   virtual void CancelRequest(RequestHandle request) = 0;
 
   // Gets the LoadState for |request|.
   virtual LoadState GetLoadState(RequestHandle request) const = 0;
 
-  // Gets the LoadState for |request|. May be called from another thread.
-  virtual LoadState GetLoadStateThreadSafe(RequestHandle request) const = 0;
-
   // The PAC script backend can be specified to the ProxyResolver either via
   // URL, or via the javascript text itself.  If |expects_pac_bytes| is true,
   // then the ProxyResolverScriptData passed to SetPacScript() should
   // contain the actual script bytes rather than just the URL.
   bool expects_pac_bytes() const { return expects_pac_bytes_; }
 
   virtual void CancelSetPacScript() = 0;
 
   // Frees any unneeded memory held by the resolver, e.g. garbage in the JS
   // engine.  Most subclasses don't need to do anything, so we provide a default
   // no-op implementation.
   virtual void PurgeMemory() {}
 
   // Called to set the PAC script backend to use.
   // Returns ERR_IO_PENDING in the case of asynchronous completion, and notifies
   // the result through |callback|.
   virtual int SetPacScript(
       const scoped_refptr<ProxyResolverScriptData>& pac_script,
       const net::CompletionCallback& callback) = 0;
 
-  // Optional shutdown code to be run before destruction. This is only used
-  // by the multithreaded runner to signal cleanup from origin thread
-  virtual void Shutdown() {}
-
  private:
   const bool expects_pac_bytes_;
 
   DISALLOW_COPY_AND_ASSIGN(ProxyResolver);
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_PROXY_RESOLVER_H_