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 82 matching lines @@
           base::Bind(&DataUseMeasurement::OnApplicationStateChange,
                      base::Unretained(this)))),
       rx_bytes_os_(0),
       tx_bytes_os_(0),
       bytes_transferred_since_last_traffic_stats_query_(0),
       no_reads_since_background_(false)
 #endif
 {
   DCHECK(ascriber_);
   DCHECK(url_request_classifier_);
+  memset(user_traffic_content_type_bytes_, 0,
+         sizeof(user_traffic_content_type_bytes_));
 
 #if defined(OS_ANDROID)
   int64_t bytes = 0;
   // Query Android traffic stats.
   if (net::android::traffic_stats::GetCurrentUidRxBytes(&bytes))
     rx_bytes_os_ = bytes;
 
   if (net::android::traffic_stats::GetCurrentUidTxBytes(&bytes))
     tx_bytes_os_ = bytes;
 #endif
@@ skipping 325 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) {
-    STATIC_HISTOGRAM_POINTER_BLOCK(
-        "DataUse.ContentType.UserTraffic", AddCount(content_type, bytes),
-        base::LinearHistogram::FactoryGet(
-            "DataUse.ContentType.UserTraffic", 1, DataUseUserData::TYPE_MAX,
-            DataUseUserData::TYPE_MAX + 1,
-            base::HistogramBase::kUmaTargetedHistogramFlag));
+    bytes += user_traffic_content_type_bytes_[content_type];
+    if (bytes >= 1024) {
+      STATIC_HISTOGRAM_POINTER_BLOCK(
+          "DataUse.ContentType.UserTrafficKB",
+          AddCount(content_type, bytes / 1024),
+          base::LinearHistogram::FactoryGet(
+              "DataUse.ContentType.UserTrafficKB", 1, DataUseUserData::TYPE_MAX,

[Ilya Sherman, 2017/05/02 21:28:52]

This histogram would still overflow if there are ~4.5 Terabytes of data used
during a single run of Chrome.  Is that level of use implausible?  Chrome's
uptime can be tremendously high: as high as months or years.  Though, I guess we
don't really tend to look at data from versions that are many months old, so
maybe that's not a big concern.

[Ilya Sherman, 2017/05/02 21:29:58]

Actually, slightly less than 4.5 TB, as I was calculating for unsigned ints. 
But, still, "single-digit terabytes" is the right order of magnitude.

+              DataUseUserData::TYPE_MAX + 1,
+              base::HistogramBase::kUmaTargetedHistogramFlag));
+    }
+    user_traffic_content_type_bytes_[content_type] = bytes % 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