Split ProxyResolver into two interfaces:...

net/proxy/proxy_resolver_null.h

-// Copyright (c) 2006-2008 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_NULL_H_
-#define NET_PROXY_PROXY_RESOLVER_NULL_H_
-
-#include "net/proxy/proxy_service.h"
-
-namespace net {
-
-// Implementation of ProxyResolver that always fails.
-class ProxyResolverNull : public ProxyResolver {
- public:
-  virtual int GetProxyConfig(ProxyConfig* config) {
-    return ERR_NOT_IMPLEMENTED;
-  }
-  virtual int GetProxyForURL(const GURL& query_url,
-                             const GURL& pac_url,
-                             ProxyInfo* results) {
-    return ERR_NOT_IMPLEMENTED;
-  }
-};
-
-}  // namespace net
-
-#endif  // NET_PROXY_PROXY_RESOLVER_NULL_H_
-