Record DRP histogram on how long back savings were cleared

components/data_reduction_proxy/core/browser/data_reduction_proxy_settings.cc

 // Copyright 2014 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_reduction_proxy/core/browser/data_reduction_proxy_settings.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 259 matching lines @@
     // Record the number of days since data reduction proxy has been enabled.
     int64_t last_enabled_time =
         prefs->GetInt64(prefs::kDataReductionProxyLastEnabledTime);
     if (last_enabled_time != 0) {
       // Record the metric only if the time when data reduction proxy was
       // enabled is available.
       RecordDaysSinceEnabledMetric(
           (clock_->Now() - base::Time::FromInternalValue(last_enabled_time))
               .InDays());
     }
+
+    int64_t last_savings_cleared_time = prefs->GetInt64(
+        prefs::kDataReductionProxySavingsClearedNegativeSystemClock);
+    if (last_savings_cleared_time != 0) {
+      int32_t days_since_savings_cleared =
+          (clock_->Now() -
+           base::Time::FromInternalValue(last_savings_cleared_time))
+              .InDays();
+
+      // Sample in the UMA histograms must be at least 1.
+      if (days_since_savings_cleared == 0)
+        days_since_savings_cleared = 1;
+      UMA_HISTOGRAM_CUSTOM_COUNTS(
+          "DataReductionProxy.DaysSinceSavingsCleared.NegativeSystemClock",
+          days_since_savings_cleared, 1, 365, 50);
+    }
   }
 
   if (spdy_proxy_auth_enabled_.GetValue() &&
       !prefs->GetBoolean(prefs::kDataReductionProxyWasEnabledBefore)) {
     prefs->SetBoolean(prefs::kDataReductionProxyWasEnabledBefore, true);
     ResetDataReductionStatistics();
   }
   if (!at_startup) {
     if (IsDataReductionProxyEnabled()) {
       RecordSettingsEnabledState(DATA_REDUCTION_SETTINGS_ACTION_OFF_TO_ON);
@@ skipping 120 matching lines @@
     int64_t data_used,
     int64_t original_size) {
   if (!IsDataReductionProxyEnabled())
     return false;
   data_reduction_proxy_service_->compression_stats()->UpdateDataSavings(
       data_usage_host, data_used, original_size);
   return true;
 }
 
 }  // namespace data_reduction_proxy