components: Cleanup class/struct fwd declarations

components/data_reduction_proxy/core/browser/data_reduction_proxy_metrics.h

 // Copyright 2014 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 COMPONENTS_DATA_REDUCTION_PROXY_CORE_BROWSER_DATA_REDUCTION_PROXY_METRICS_H_
 #define COMPONENTS_DATA_REDUCTION_PROXY_CORE_BROWSER_DATA_REDUCTION_PROXY_METRICS_H_
 
 #include <vector>
 
 namespace net {
 class ProxyConfig;
 class URLRequest;
 }
 
-class PrefService;
-
 namespace data_reduction_proxy {
 
 class DataReductionProxyConfig;
 
 typedef std::vector<long long> ContentLengthList;
 
 // A bypass delay more than this is treated as a long delay.
 const int kLongBypassDelayInSeconds = 30 * 60;
 
 // The number of days of bandwidth usage statistics that are tracked.
@@ skipping 20 matching lines @@
 
 // Returns DataReductionProxyRequestType for |request|.
 DataReductionProxyRequestType GetDataReductionProxyRequestType(
     const net::URLRequest& request,
     const net::ProxyConfig& data_reduction_proxy_config,
     const DataReductionProxyConfig& config);
 
 }  // namespace data_reduction_proxy
 
 #endif  // COMPONENTS_DATA_REDUCTION_PROXY_CORE_BROWSER_DATA_REDUCTION_PROXY_METRICS_H_