UMA for data savings displayed to users.

components/data_reduction_proxy/core/browser/data_reduction_proxy_compression_stats.cc

Index: components/data_reduction_proxy/core/browser/data_reduction_proxy_compression_stats.cc
diff --git a/components/data_reduction_proxy/core/browser/data_reduction_proxy_compression_stats.cc b/components/data_reduction_proxy/core/browser/data_reduction_proxy_compression_stats.cc
index 5655e12c92fdd4fc8fe6f62922396b85505649df..ebacdbf6df7338bd9148f3a1182e67d168c94a50 100644
--- a/components/data_reduction_proxy/core/browser/data_reduction_proxy_compression_stats.cc
+++ b/components/data_reduction_proxy/core/browser/data_reduction_proxy_compression_stats.cc
@@ -704,6 +704,7 @@ void DataReductionProxyCompressionStats::RecordContentLengthPrefs(
     // Here, we prefer collecting less data but the collected data is
     // associated with an accurate date.
     if (days_since_last_update == 1) {
+      RecordUserVisibleDataSavings();
       // The previous day's data point is the second one from the tail.
       // Therefore (kNumDaysInHistory - 2) below.
       RecordDailyContentLengthHistograms(
@@ -721,4 +722,27 @@ void DataReductionProxyCompressionStats::RecordContentLengthPrefs(
   }
 }
 
+void DataReductionProxyCompressionStats::RecordUserVisibleDataSavings() {
+  int64 original_content_length;
+  int64 received_content_length;
+  int64 last_update_internal;
+  GetContentLengths(kNumDaysInHistorySummary, &original_content_length,
+                    &received_content_length, &last_update_internal);
+
+  if (original_content_length == 0) {

[Alexei Svitkine (slow), 2015/06/05 18:01:43]

Nit: Most of Chromium style prefers no {}'s for 1-liners.

[Not at Google. Contact bengr, 2015/06/05 18:36:10]

Done.

+    return;
+  }
+
+  int64 user_visible_savings_bytes =
+      original_content_length - received_content_length;
+  int user_visible_savings_percent =
+      user_visible_savings_bytes * 100 / original_content_length;
+  UMA_HISTOGRAM_PERCENTAGE(
+      "Net.DailyUserVisibleSavingsPercent_DataRedictionProxyEnabled",
+      user_visible_savings_percent);
+  UMA_HISTOGRAM_COUNTS(
+      "Net.DailyUserVisibleSavingsSize_DataRedictionProxyEnabled",
+      user_visible_savings_bytes >> 10);
+}
+
 }  // namespace data_reduction_proxy