components: Cleanup class/struct fwd declarations

components/data_reduction_proxy/core/common/data_reduction_proxy_event_store.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_COMMON_DATA_REDUCTION_PROXY_EVENT_STORE_H_
 #define COMPONENTS_DATA_REDUCTION_PROXY_CORE_COMMON_DATA_REDUCTION_PROXY_EVENT_STORE_H_
 
 #include <stdint.h>
 
 #include <deque>
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
 #include "base/threading/thread_checker.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_event_storage_delegate.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_headers.h"
 
 namespace base {
 class DictionaryValue;
-class TimeDelta;
 class Value;
 }
 
 namespace data_reduction_proxy {
 
 class DataReductionProxyEventStore
     : public DataReductionProxyEventStorageDelegate {
  public:
   // Adds data reduction proxy specific constants to the net_internals
   // constants dictionary.
@@ skipping 56 matching lines @@
 
   // Enforce usage on the UI thread.
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(DataReductionProxyEventStore);
 };
 
 }  // namespace data_reduction_proxy
 
 #endif  // COMPONENTS_DATA_REDUCTION_PROXY_CORE_COMMON_DATA_REDUCTION_PROXY_EVENT_STORE_H_