Add external data use observer

components/data_usage/core/data_use_aggregator.cc

 // 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.
 
 #include "components/data_usage/core/data_use_aggregator.h"
 
 #include "net/base/network_change_notifier.h"
 #include "net/url_request/url_request.h"
 
 namespace data_usage {
@@ skipping 30 matching lines @@
 }
 
 void DataUseAggregator::ReportOffTheRecordDataUse(int64_t tx_bytes,
                                                   int64_t rx_bytes) {
   DCHECK(thread_checker_.CalledOnValidThread());
   // TODO(sclittle): Once data usage amortization is implemented, keep track of
   // the off-the-record bytes so that they can be taken out of the amortized
   // data usage calculations if applicable.
 }
 
+void DataUseAggregator::PassExternalObserver(
+    scoped_ptr<Observer> external_observer) {
+  external_observer_ = external_observer.Pass();
+}
+
 void DataUseAggregator::NotifyDataUse(
     const std::vector<DataUse>& data_use_sequence) {
   DCHECK(thread_checker_.CalledOnValidThread());
   FOR_EACH_OBSERVER(Observer, observer_list_, OnDataUse(data_use_sequence));
 }
 
 }  // namespace data_usage