UMA for data savings displayed to users.

Daily reported UMA for number of bytes and data savings percent over the
past 30 days.

Review URL: https://codereview.chromium.org/1167543010

Cr-Commit-Position: refs/heads/master@{#333136}

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 +722,26 @@ 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)
+    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

components/data_reduction_proxy/core/browser/data_reduction_proxy_compression_stats.h

@@ -132,6 +132,11 @@ class DataReductionProxyCompressionStats {
                                 DataReductionProxyRequestType request_type,
                                 base::Time now);
 
+  // Record UMA with data savings bytes and percent over the past
+  // |DataReductionProxy::kNumDaysInHistorySummary| days. These numbers
+  // are displayed to users as their data savings.
+  void RecordUserVisibleDataSavings();
+
   PrefService* pref_service_;
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
   const base::TimeDelta delay_;

tools/metrics/histograms/histograms.xml

@@ -19577,6 +19577,28 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Net.DailyUserVisibleSavingsPercent_DataRedictionProxyEnabled"
+    units="Percent">
+  <owner>kundaji@chromium.org</owner>
+  <owner>bengr@chromium.org</owner>
+  <summary>
+    The percentage of data savings in past
+    |DataReductionProxy::kNumDaysInHistorySummary| days. This number is
+    displayed to users as their data savings.
+  </summary>
+</histogram>
+
+<histogram name="Net.DailyUserVisibleSavingsSize_DataRedictionProxyEnabled"
+    units="KB">
+  <owner>kundaji@chromium.org</owner>
+  <owner>bengr@chromium.org</owner>
+  <summary>
+    The total data saved in KB in past
+    |DataReductionProxy::kNumDaysInHistorySummary| days. This number is used to
+    compute the data savings displayed to the user.
+  </summary>
+</histogram>
+
 <histogram name="Net.DhcpWpadCancelTime" units="milliseconds">
   <obsolete>
     Removed in Chrome 39.