chrome: Cleanup class/struct forward declarations

chrome/browser/net/dns_probe_service.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 CHROME_BROWSER_NET_DNS_PROBE_SERVICE_H_
 #define CHROME_BROWSER_NET_DNS_PROBE_SERVICE_H_
 
 #include <memory>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/macros.h"
 #include "base/time/time.h"
 #include "chrome/browser/net/dns_probe_runner.h"
 #include "components/error_page/common/net_error_info.h"
 #include "net/base/network_change_notifier.h"
 
 namespace net {
 class DnsClient;
-struct DnsConfig;
 }
 
 namespace chrome_browser_net {
 
 // Probes the system and public DNS servers to determine the (probable) cause
 // of a recent DNS-related page load error.  Coalesces multiple probe requests
 // (perhaps from multiple tabs) and caches the results.
 //
 // Uses a single DNS attempt per config, and doesn't randomize source ports.
 class DnsProbeService : public net::NetworkChangeNotifier::DNSObserver {
@@ skipping 42 matching lines @@
   // DnsProbeRunners for the system DNS configuration and a public DNS server.
   DnsProbeRunner system_runner_;
   DnsProbeRunner public_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(DnsProbeService);
 };
 
 }  // namespace chrome_browser_net
 
 #endif  // CHROME_BROWSER_NET_DNS_PROBE_SERVICE_H_