Amortize data usage using TrafficStats on Android.

components/data_usage/core/data_use_aggregator.h

Index: components/data_usage/core/data_use_aggregator.h
diff --git a/components/data_usage/core/data_use_aggregator.h b/components/data_usage/core/data_use_aggregator.h
index 36d8ef09016c01c11fa1e8f58ae2af1b21cd7f50..50bb36ede988215a42fb9fa319bbc95d7da95735 100644
--- a/components/data_usage/core/data_use_aggregator.h
+++ b/components/data_usage/core/data_use_aggregator.h
@@ -12,7 +12,6 @@
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
-#include "base/memory/scoped_vector.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
 #include "base/threading/thread_checker.h"
@@ -24,6 +23,7 @@ class URLRequest;
 
 namespace data_usage {
 
+class DataUseAmortizer;
 class DataUseAnnotator;
 struct DataUse;
 
@@ -41,9 +41,12 @@ class DataUseAggregator
         const std::vector<const DataUse*>& data_use_sequence) = 0;
   };
 
-  // Constructs a new DataUseAggregator with the given |annotator|. A NULL
-  // annotator will be treated as a no-op annotator.
-  explicit DataUseAggregator(scoped_ptr<DataUseAnnotator> annotator);
+  // Constructs a new DataUseAggregator with the given |annotator| and
+  // |amortizer|. A NULL |annotator| will be treated as a no-op annotator, and a
+  // NULL |amortizer| will be treated as a no-op amortizer.
+  DataUseAggregator(scoped_ptr<DataUseAnnotator> annotator,
+                    scoped_ptr<DataUseAmortizer> amortizer);
+
   ~DataUseAggregator() override;
 
   void AddObserver(Observer* observer);
@@ -73,20 +76,18 @@ class DataUseAggregator
   void SetMccMncForTests(const std::string& mcc_mnc);
 
  private:
-  // Appends |data_use| to the buffer of unreported data use and prepares to
-  // notify observers.
-  void AppendDataUse(scoped_ptr<DataUse> data_use);
+  // Passes |data_use| to |amortizer_| if it exists, or calls
+  // OnAmortizationComplete directly if |amortizer_| doesn't exist.
+  void PassDataUseToAmortizer(scoped_ptr<DataUse> data_use);
 
-  // Flush any buffered data use and notify observers.
-  void FlushBufferedDataUse();
+  // Notifies observers with the data use from |amortized_data_use|.
+  void OnAmortizationComplete(scoped_ptr<DataUse> amortized_data_use);
 
   base::ThreadChecker thread_checker_;
   scoped_ptr<DataUseAnnotator> annotator_;
+  scoped_ptr<DataUseAmortizer> amortizer_;
   base::ObserverList<Observer> observer_list_;
 
-  // Buffer of unreported data use.
-  ScopedVector<DataUse> buffered_data_use_;
-
   // Current connection type as notified by NetworkChangeNotifier.
   net::NetworkChangeNotifier::ConnectionType connection_type_;
 
@@ -95,15 +96,6 @@ class DataUseAggregator
   // even if the current active network is not a cellular network.
   std::string mcc_mnc_;
 
-  // The total amount of off-the-record data usage that has happened since the
-  // last time the buffer was flushed.
-  int64_t off_the_record_tx_bytes_since_last_flush_;
-  int64_t off_the_record_rx_bytes_since_last_flush_;
-
-  // Indicates if a FlushBufferedDataUse() callback has been posted to run later
-  // on the IO thread.
-  bool is_flush_pending_;
-
   base::WeakPtrFactory<DataUseAggregator> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DataUseAggregator);