Record DRP histogram on how long back savings were cleared

components/data_reduction_proxy/core/browser/data_reduction_proxy_settings_unittest.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 <stddef.h>
 #include <stdint.h>
 
 #include <vector>
@@ skipping 713 matching lines @@
 
   // Simulate Chromium startup with data reduction proxy already enabled.
   settings_->spdy_proxy_auth_enabled_.SetValue(true);
   settings_->MaybeActivateDataReductionProxy(true /* at_startup */);
   test_context_->RunUntilIdle();
   histogram_tester.ExpectTotalCount("DataReductionProxy.DaysSinceEnabled", 0);
   EXPECT_EQ(0, test_context_->pref_service()->GetInt64(
                    prefs::kDataReductionProxyLastEnabledTime));
 }
 
+TEST_F(DataReductionProxySettingsTest, TestDaysSinceSavingsCleared) {
+  std::unique_ptr<base::SimpleTestClock> clock(new base::SimpleTestClock());
+  base::SimpleTestClock* clock_ptr = clock.get();
+  clock_ptr->Advance(base::TimeDelta::FromDays(1));
+  ResetSettings(std::move(clock), true, true, false, false);
+
+  InitPrefMembers();
+  base::HistogramTester histogram_tester;
+  test_context_->pref_service()->SetInt64(
+      prefs::kDataReductionProxySavingsClearedNegativeSystemClock,
+      clock_ptr->Now().ToInternalValue());
+
+  settings_->data_reduction_proxy_service_->SetIOData(
+      test_context_->io_data()->GetWeakPtr());
+  test_context_->RunUntilIdle();
+
+  clock_ptr->Advance(base::TimeDelta::FromDays(100));
+
+  // Simulate Chromium startup with data reduction proxy already enabled.
+  settings_->spdy_proxy_auth_enabled_.SetValue(true);
+  settings_->MaybeActivateDataReductionProxy(true /* at_startup */);
+  test_context_->RunUntilIdle();
+  histogram_tester.ExpectUniqueSample(
+      "DataReductionProxy.DaysSinceSavingsCleared.NegativeSystemClock", 100, 1);
+}
+
 TEST_F(DataReductionProxySettingsTest, TestGetDailyContentLengths) {
   ContentLengthList result =
       settings_->GetDailyContentLengths(prefs::kDailyHttpOriginalContentLength);
 
   ASSERT_FALSE(result.empty());
   ASSERT_EQ(kNumDaysInHistory, result.size());
 
   for (size_t i = 0; i < kNumDaysInHistory; ++i) {
     long expected_length =
         static_cast<long>((kNumDaysInHistory - 1 - i) * 2);
@@ skipping 18 matching lines @@
       test_context_->CreateDataReductionProxyService(settings_.get()));
   settings_->SetCallbackToRegisterSyntheticFieldTrial(
       base::Bind(&DataReductionProxySettingsTestBase::
                  SyntheticFieldTrialRegistrationCallback,
                  base::Unretained(this)));
 
   test_context_->RunUntilIdle();
 }
 
 }  // namespace data_reduction_proxy