Improve performance of proxy resolver by tracing DNS dependencies.

net/proxy/proxy_resolver_request_context.h

-// Copyright (c) 2010 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_REQUEST_CONTEXT_H_
-#define NET_PROXY_PROXY_RESOLVER_REQUEST_CONTEXT_H_
-
-namespace net {
-
-class HostCache;
-class BoundNetLog;
-
-// This data structure holds state related to an invocation of
-// "FindProxyForURL()". It is used to associate per-request
-// data that can be retrieved by the bindings.
-struct ProxyResolverRequestContext {
-  // All of these pointers are expected to remain valid for duration of
-  // this instance's lifetime.
-  ProxyResolverRequestContext(const BoundNetLog* net_log,
-                              HostCache* host_cache)
-    : net_log(net_log),
-      host_cache(host_cache) {
-  }
-
-  const BoundNetLog* net_log;
-  HostCache* host_cache;
-};
-
-}  // namespace net
-
-#endif  // NET_PROXY_PROXY_RESOLVER_REQUEST_CONTEXT_H_