Minor refactor to get rid of a friend association

components/data_use_measurement/core/data_use.cc

 // Copyright 2016 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.
 
 #include "components/data_use_measurement/core/data_use.h"
 
 namespace data_use_measurement {
 
 DataUse::DataUse(TrafficType traffic_type)
     : traffic_type_(traffic_type),
       total_bytes_sent_(0),
       total_bytes_received_(0) {}
 
 DataUse::~DataUse() {}
 
+void DataUse::IncrementTotalBytes(int64_t bytes_received, int64_t bytes_sent) {
+  total_bytes_received_ += bytes_received;
+  total_bytes_sent_ += bytes_sent;
+}
+
 void DataUse::MergeFrom(const DataUse& other) {
   // Traffic type need not be same while merging. One of the data use created
   // when mainframe is created could have UNKNOWN traffic type, and later merged
   // with the data use created for its mainframe request which could be
   // USER_TRAFFIC.
   total_bytes_sent_ += other.total_bytes_sent_;
   total_bytes_received_ += other.total_bytes_received_;
 }
 
 }  // namespace data_use_measurement