Fix overflow in user traffic content type histogram

components/data_use_measurement/core/data_use_measurement.cc

Index: components/data_use_measurement/core/data_use_measurement.cc
diff --git a/components/data_use_measurement/core/data_use_measurement.cc b/components/data_use_measurement/core/data_use_measurement.cc
index fcebeb8d070d079520f1ebde9a28275fcd20bc27..ae06587c3a3db704e0787d2744be5bd5419561cf 100644
--- a/components/data_use_measurement/core/data_use_measurement.cc
+++ b/components/data_use_measurement/core/data_use_measurement.cc
@@ -445,12 +445,16 @@ void DataUseMeasurement::RecordContentTypeHistogram(
   // 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),