Amortize data usage using TrafficStats on Android.

components/data_usage/core/BUILD.gn

 # 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.
 
 source_set("core") {
   sources = [
     "data_use.cc",
     "data_use.h",
     "data_use_aggregator.cc",
     "data_use_aggregator.h",
+    "data_use_amortizer.h",
     "data_use_annotator.h",
   ]
   deps = [
     "//base",
     "//net",
     "//url",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "data_use_aggregator_unittest.cc",
   ]
 
   configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 
   deps = [
     ":core",
     "//base",
     "//base/test:test_support",
     "//net:test_support",
     "//testing/gtest",
   ]
 }