Amortize data usage using TrafficStats on Android.

components/data_usage/core/data_use_amortizer.h

Index: components/data_usage/core/data_use_amortizer.h
diff --git a/components/data_usage/core/data_use_amortizer.h b/components/data_usage/core/data_use_amortizer.h
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+// 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_AMORTIZER_H_
+#define COMPONENTS_DATA_USAGE_CORE_DATA_USE_AMORTIZER_H_
+
+#include <stdint.h>
+
+#include "base/callback.h"
+#include "base/memory/scoped_ptr.h"
+
+namespace data_usage {
+
+struct DataUse;
+
+// Class that takes in DataUse and amortizes any extra data usage overhead
+// across DataUse objects.
+class DataUseAmortizer {
+ public:
+  typedef base::Callback<void(scoped_ptr<DataUse>)>
+      AmortizationCompleteCallback;
+
+  virtual ~DataUseAmortizer() {}
+
+  // Amortizes overhead into |data_use|, then passes the it to |callback| once
+  // amortization is complete. Amortizers that perform buffering may combine
+  // together |data_use| objects with the same |callback| if the |data_use|
+  // objects are identical in all ways but their byte counts.
+  virtual void AmortizeDataUse(
+      scoped_ptr<DataUse> data_use,
+      const AmortizationCompleteCallback& callback) = 0;
+
+  // Notifies the DataUseAmortizer that some extra bytes have been transferred
+  // that aren't associated with any DataUse objects (e.g. off-the-record
+  // traffic).
+  virtual void OnExtraBytes(int64_t extra_tx_bytes, int64_t extra_rx_bytes) = 0;
+};
+
+}  // namespace data_usage
+
+#endif  // COMPONENTS_DATA_USAGE_CORE_DATA_USE_AMORTIZER_H_