Re-use callback objects in the DataUseAggregator.

components/data_usage/core/data_use_aggregator.h

 // Copyright 2015 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_USAGE_CORE_DATA_USE_AGGREGATOR_H_
 #define COMPONENTS_DATA_USAGE_CORE_DATA_USE_AGGREGATOR_H_
 
 #include <stdint.h>
 
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
 #include "base/threading/thread_checker.h"
+#include "components/data_usage/core/data_use_amortizer.h"
+#include "components/data_usage/core/data_use_annotator.h"
 #include "net/base/network_change_notifier.h"
 
 namespace net {
 class URLRequest;
 }
 
 namespace data_usage {
 
-class DataUseAmortizer;
-class DataUseAnnotator;
 struct DataUse;
 
 // Class that collects and aggregates network usage, reporting the usage to
 // observers. Should only be used on the IO thread.
 class DataUseAggregator
     : public net::NetworkChangeNotifier::ConnectionTypeObserver {
  public:
   class Observer {
    public:
     virtual ~Observer() {}
@@ skipping 51 matching lines @@
   base::ObserverList<Observer> observer_list_;
 
   // Current connection type as notified by NetworkChangeNotifier.
   net::NetworkChangeNotifier::ConnectionType connection_type_;
 
   // MCC+MNC (mobile country code + mobile network code) of the current SIM
   // provider.  Set to empty string if SIM is not present. |mcc_mnc_| is set
   // even if the current active network is not a cellular network.
   std::string mcc_mnc_;
 
+  // As an optimization, re-use the same callbacks to avoid creating and
+  // allocating a new Callback object for each call into the |annotator_| or
+  // |amortizer_|. These callbacks are lazily initialized.
+  DataUseAnnotator::DataUseConsumerCallback annotation_callback_;
+  DataUseAmortizer::AmortizationCompleteCallback amortization_callback_;
+
   base::WeakPtrFactory<DataUseAggregator> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DataUseAggregator);
 };
 
 }  // namespace data_usage
 
 #endif  // COMPONENTS_DATA_USAGE_CORE_DATA_USE_AGGREGATOR_H_