Make domain mixing metrics time lengths more explicit.

The test part of this change is necessary to support running HistoryBackend on
the ThreadPool.(Feature:HistoryServiceUsesTaskScheduler) On the ThreaPoool  we cannot
FastForwardUntilNoTasksRemain() for tasks using repeating timers.

Regardless of the new feature this change is intended to be a no-op and has
the added benefit of being more explicit in the time related expectations.

Bug: 661143
Change-Id: I1dcd2f3e2d1e5a5455953b0555c6475b2d0fdafd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1932417Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Cait Phillips <caitkp@chromium.org>
Auto-Submit: Oliver Li <olivierli@chromium.org>
Commit-Queue: Oliver Li <olivierli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719223}

chrome/browser/google/google_search_domain_mixing_metrics_emitter_unittest.cc

@@ -8,6 +8,7 @@
 #include "base/test/metrics/histogram_tester.h"
 #include "base/test/simple_test_clock.h"
 #include "base/timer/mock_timer.h"
+#include "components/history/core/browser/domain_mixing_metrics.h"
 #include "components/history/core/browser/history_service.h"
 #include "components/history/core/browser/history_types.h"
 #include "components/history/core/test/history_service_test_util.h"
@@ -152,7 +153,11 @@ TEST_F(GoogleSearchDomainMixingMetricsEmitterTest, EmitsMetricsOnStart) {
   emitter_->Start();
 
   base::HistogramTester tester;
-  task_environment_.FastForwardUntilNoTasksRemain();
+
+  // Fast forward far enough that histograms have been written to for all
+  // intervals.
+  task_environment_.FastForwardBy(
+      base::TimeDelta::FromDays(history::kOneMonth));
   BlockUntilHistoryProcessesPendingRequests(history_service_.get());
   VerifyHistograms(tester);
 }
@@ -173,8 +178,10 @@ TEST_F(GoogleSearchDomainMixingMetricsEmitterTest, EmitsMetricsWhenTimerFires) {
   // Start the emitter.
   emitter_->Start();
 
-  // Wait for the first run to be done.
-  task_environment_.FastForwardUntilNoTasksRemain();
+  // Fast forward far enough that histograms have been written to for all
+  // intervals.
+  task_environment_.FastForwardBy(
+      base::TimeDelta::FromDays(history::kOneMonth));
   BlockUntilHistoryProcessesPendingRequests(history_service_.get());
 
   // last_metrics_time is expected to have been incremented.
@@ -195,7 +202,10 @@ TEST_F(GoogleSearchDomainMixingMetricsEmitterTest, EmitsMetricsWhenTimerFires) {
   timer_->Fire();
 
   base::HistogramTester tester;
-  task_environment_.FastForwardUntilNoTasksRemain();
+  // Fast forward far enough that histograms have been written to for all
+  // intervals.
+  task_environment_.FastForwardBy(
+      base::TimeDelta::FromDays(history::kOneMonth));
   BlockUntilHistoryProcessesPendingRequests(history_service_.get());
   VerifyHistograms(tester);
 

components/history/core/browser/domain_mixing_metrics.cc

@@ -21,7 +21,7 @@ using DomainVisitsPerDay = base::flat_map<Day, DomainVisits>;
 // The time intervals in days to compute domain mixing metrics for, sorted
 // in ascending order.
 std::vector<int> NumDaysForMetrics() {
-  return {1, 7, 14, 30};
+  return {kOneDay, kOneWeek, kTwoWeeks, kOneMonth};
 }
 
 // Maps a time to the start of a day using ref_start_of_day as the reference
@@ -87,16 +87,16 @@ void EmitDomainMixingMetric(const DomainVisits& domain_visits, int num_days) {
   double domain_mixing_ratio = ComputeDomainMixingRatio(domain_visits);
   int percentage = gfx::ToRoundedInt(100 * domain_mixing_ratio);
   switch (num_days) {
-    case 1:
+    case kOneDay:
       UMA_HISTOGRAM_PERCENTAGE("DomainMixing.OneDay", percentage);
       break;
-    case 7:
+    case kOneWeek:
       UMA_HISTOGRAM_PERCENTAGE("DomainMixing.OneWeek", percentage);
       break;
-    case 14:
+    case kTwoWeeks:
       UMA_HISTOGRAM_PERCENTAGE("DomainMixing.TwoWeeks", percentage);
       break;
-    case 30:
+    case kOneMonth:
       UMA_HISTOGRAM_PERCENTAGE("DomainMixing.OneMonth", percentage);
       break;
     default:
@@ -147,4 +147,4 @@ void EmitDomainMixingMetrics(const std::vector<DomainVisit>& domain_visits,
   }
 }
 
-}  // namespace history
\ No newline at end of file
+}  // namespace history

components/history/core/browser/domain_mixing_metrics.h

@@ -13,6 +13,11 @@
 
 namespace history {
 
+constexpr int kOneDay = 1;
+constexpr int kOneWeek = 7;
+constexpr int kTwoWeeks = 14;
+constexpr int kOneMonth = 30;
+
 // Emits domain mixing metrics given a list of domain visits and the start of
 // the first day to compute metrics for.
 //
@@ -32,4 +37,4 @@ void EmitDomainMixingMetrics(const std::vector<DomainVisit>& domain_visits,
 
 }  // namespace history
 
-#endif
\ No newline at end of file
+#endif  // COMPONENTS_HISTORY_CORE_BROWSER_DOMAIN_MIXING_METRICS_H_