Fix overflow in user traffic content type histogram

components/data_use_measurement/core/data_use_measurement.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_use_measurement/core/data_use_measurement.h"
 
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/strings/stringprintf.h"
 #include "build/build_config.h"
@@ skipping 427 matching lines @@
                                           : DataUseUserData::AUDIO);
   } else if (content_type == DataUseUserData::VIDEO) {
     content_type = app_state != DataUseUserData::FOREGROUND
                        ? DataUseUserData::VIDEO_APPBACKGROUND
                        : (!is_tab_visible ? DataUseUserData::VIDEO_TABBACKGROUND
                                           : DataUseUserData::VIDEO);
   }
   // Use the more primitive STATIC_HISTOGRAM_POINTER_BLOCK macro because the
   // simple UMA_HISTOGRAM_ENUMERATION macros don't expose 'AddCount'.
   if (is_user_traffic) {
+    user_traffic_content_type_bytes_[content_type] += bytes;

[RyanSturm, 2017/05/01 18:49:44]

You might want to capture the foreground/background state here. If you are
storing 500B of background data and a new request starts and finishes entirely
in foreground, will the 500B get attributed to foreground instead of
ambiguous/background?

[Raj, 2017/05/01 20:57:58]

This CL only changes the UMA DataUse.ContentType.UserTrafficKB which does not
have BG/FG distinction in name.
The content_type already captures video/audio in BG/FG explicitly. So the bytes
go in the appropriate user_traffic_content_type_bytes[] bucket.

[RyanSturm, 2017/05/01 21:05:24]

Thanks for the clarification.

     STATIC_HISTOGRAM_POINTER_BLOCK(
-        "DataUse.ContentType.UserTraffic", AddCount(content_type, bytes),
+        "DataUse.ContentType.UserTrafficKB",
+        AddCount(content_type,
+                 user_traffic_content_type_bytes_[content_type] / 1024),
         base::LinearHistogram::FactoryGet(
-            "DataUse.ContentType.UserTraffic", 1, DataUseUserData::TYPE_MAX,
+            "DataUse.ContentType.UserTrafficKB", 1, DataUseUserData::TYPE_MAX,
             DataUseUserData::TYPE_MAX + 1,
             base::HistogramBase::kUmaTargetedHistogramFlag));
+    user_traffic_content_type_bytes_[content_type] %= 1024;
   } else {
     STATIC_HISTOGRAM_POINTER_BLOCK(
         "DataUse.ContentType.Services", AddCount(content_type, bytes),
         base::LinearHistogram::FactoryGet(
             "DataUse.ContentType.Services", 1, DataUseUserData::TYPE_MAX,
             DataUseUserData::TYPE_MAX + 1,
             base::HistogramBase::kUmaTargetedHistogramFlag));
   }
 }
 
 void DataUseMeasurement::RecordPageTransitionUMA(
     const net::URLRequest& request) const {
   if (!url_request_classifier_->IsUserRequest(request))
     return;
 
   const DataUseRecorder* recorder = ascriber_->GetDataUseRecorder(request);
   if (recorder) {
     url_request_classifier_->RecordPageTransitionUMA(
         recorder->page_transition(), request.GetTotalReceivedBytes());
   }
 }
 
 }  // namespace data_use_measurement