Record DRP histogram on how long back savings were cleared

components/data_reduction_proxy/core/browser/data_reduction_proxy_prefs.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_prefs.h"
 
 #include <memory>
 
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_pref_names.h"
 #include "components/pref_registry/pref_registry_syncable.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
 #include "components/prefs/scoped_user_pref_update.h"
 
 namespace data_reduction_proxy {
 
 // Make sure any changes here that have the potential to impact android_webview
 // are reflected in RegisterSimpleProfilePrefs.
 void RegisterSyncableProfilePrefs(user_prefs::PrefRegistrySyncable* registry) {
   registry->RegisterBooleanPref(prefs::kDataReductionProxyWasEnabledBefore,
                                 false);
 
   registry->RegisterInt64Pref(prefs::kDataReductionProxyLastEnabledTime, 0L);
+  registry->RegisterInt64Pref(
+      prefs::kDataReductionProxySavingsClearedNegativeSystemClock, 0);
 
   registry->RegisterBooleanPref(prefs::kDataUsageReportingEnabled, false);
 
   registry->RegisterInt64Pref(prefs::kHttpReceivedContentLength, 0);
   registry->RegisterInt64Pref(prefs::kHttpOriginalContentLength, 0);
 
   registry->RegisterListPref(prefs::kDailyHttpOriginalContentLength);
   registry->RegisterInt64Pref(prefs::kDailyHttpOriginalContentLengthApplication,
                               0L);
   registry->RegisterInt64Pref(prefs::kDailyHttpOriginalContentLengthVideo, 0L);
@@ skipping 67 matching lines @@
   registry->RegisterBooleanPref(prefs::kDataUsageReportingEnabled, false);
   RegisterPrefs(registry);
 }
 
 // Add any new data reduction proxy prefs to the |pref_map_| or the
 // |list_pref_map_| in Init() of DataReductionProxyCompressionStats.
 void RegisterPrefs(PrefRegistrySimple* registry) {
   registry->RegisterStringPref(prefs::kDataReductionProxy, std::string());
   registry->RegisterInt64Pref(prefs::kDataReductionProxyLastEnabledTime, 0L);
   registry->RegisterInt64Pref(
-      prefs::kHttpReceivedContentLength, 0);
+      prefs::kDataReductionProxySavingsClearedNegativeSystemClock, 0);
+  registry->RegisterInt64Pref(prefs::kHttpReceivedContentLength, 0);
   registry->RegisterInt64Pref(
       prefs::kHttpOriginalContentLength, 0);
   registry->RegisterListPref(
       prefs::kDailyHttpOriginalContentLength);
   registry->RegisterInt64Pref(prefs::kDailyHttpOriginalContentLengthApplication,
                               0L);
   registry->RegisterInt64Pref(prefs::kDailyHttpOriginalContentLengthVideo, 0L);
   registry->RegisterInt64Pref(prefs::kDailyHttpOriginalContentLengthUnknown,
                               0L);
   registry->RegisterListPref(prefs::kDailyHttpReceivedContentLength);
@@ skipping 49 matching lines @@
   registry->RegisterIntegerPref(prefs::kLoFiImplicitOptOutEpoch, 0);
   registry->RegisterIntegerPref(prefs::kLoFiUIShownPerSession, 0);
   registry->RegisterIntegerPref(prefs::kLoFiLoadImagesPerSession, 0);
   registry->RegisterIntegerPref(prefs::kLoFiConsecutiveSessionDisables, 0);
   registry->RegisterBooleanPref(prefs::kLoFiWasUsedThisSession, false);
   registry->RegisterInt64Pref(prefs::kSimulatedConfigRetrieveTime, 0L);
   registry->RegisterStringPref(prefs::kDataReductionProxyConfig, std::string());
 }
 
 }  // namespace data_reduction_proxy