Improve performance of proxy resolver by tracing DNS dependencies.

net/proxy/sync_host_resolver_bridge.h

-// Copyright (c) 2012 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_SYNC_HOST_RESOLVER_BRIDGE_H_
-#define NET_PROXY_SYNC_HOST_RESOLVER_BRIDGE_H_
-
-#include "base/compiler_specific.h"
-#include "base/memory/ref_counted.h"
-#include "net/proxy/sync_host_resolver.h"
-
-class MessageLoop;
-
-namespace net {
-
-// Wrapper around HostResolver to give a sync API while running the resolver
-// in async mode on |host_resolver_loop|.
-class NET_EXPORT_PRIVATE SyncHostResolverBridge : public SyncHostResolver {
- public:
-  SyncHostResolverBridge(HostResolver* host_resolver,
-                         MessageLoop* host_resolver_loop);
-
-  virtual ~SyncHostResolverBridge();
-
-  // SyncHostResolver methods:
-  virtual int Resolve(const HostResolver::RequestInfo& info,
-                      AddressList* addresses,
-                      const BoundNetLog& net_log) OVERRIDE;
-
-  // The Shutdown() method should be called prior to destruction, from
-  // |host_resolver_loop_|. It aborts any in progress synchronous resolves, to
-  // prevent deadlocks from happening.
-  virtual void Shutdown() OVERRIDE;
-
- private:
-  class Core;
-
-  MessageLoop* const host_resolver_loop_;
-  scoped_refptr<Core> core_;
-  DISALLOW_COPY_AND_ASSIGN(SyncHostResolverBridge);
-};
-
-}  // namespace net
-
-#endif  // NET_PROXY_SYNC_HOST_RESOLVER_BRIDGE_H_