predictors: Stop reporting several ResourcePrefetchPredictor histograms

The data collected for the following histograms have not been used recently:
- ResourcePrefetchPredictor.PrefetchingDuration
- ResourcePrefetchPredictor.ReportingEvent

Bug: 900064
Change-Id: I4f1d6b479c1a5a1f1a5c30160322acd436fcbc8c
Reviewed-on: https://chromium-review.googlesource.com/c/1343091Reviewed-by: Benoit L <lizeb@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Commit-Queue: Alexandr Ilin <alexilin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610199}

chrome/browser/predictors/loading_predictor.cc

@@ -91,12 +91,12 @@ void LoadingPredictor::PrepareForPageLoad(const GURL& url,
   has_preconnect_prediction =
       AddInitialUrlToPreconnectPrediction(url, &prediction);
 
-  if (has_preconnect_prediction) {
-    // To report hint durations and deduplicate hints to the same url.
-    active_hints_.emplace(url, base::TimeTicks::Now());
-    if (IsPreconnectAllowed(profile_))
-      MaybeAddPreconnect(url, std::move(prediction.requests), origin);
-  }
+  if (!has_preconnect_prediction)
+    return;
+
+  active_hints_.emplace(url, base::TimeTicks::Now());
+  if (IsPreconnectAllowed(profile_))
+    MaybeAddPreconnect(url, std::move(prediction.requests), origin);
 }
 
 void LoadingPredictor::CancelPageLoadHint(const GURL& url) {
@@ -169,9 +169,6 @@ std::map<GURL, base::TimeTicks>::iterator LoadingPredictor::CancelActiveHint(
 
   const GURL& url = hint_it->first;
   MaybeRemovePreconnect(url);
-  UMA_HISTOGRAM_TIMES(
-      internal::kResourcePrefetchPredictorPrefetchingDurationHistogram,
-      base::TimeTicks::Now() - hint_it->second);
   return active_hints_.erase(hint_it);
 }
 

chrome/browser/predictors/loading_predictor_unittest.cc

@@ -145,38 +145,6 @@ void LoadingPredictorPreconnectTest::SetPreference() {
       chrome_browser_net::NETWORK_PREDICTION_ALWAYS);
 }
 
-TEST_F(LoadingPredictorTest, TestPrefetchingDurationHistogram) {
-  base::HistogramTester histogram_tester;
-  const GURL url = GURL(kUrl);
-  const GURL url2 = GURL(kUrl2);
-  const GURL url3 = GURL(kUrl3);
-
-  predictor_->PrepareForPageLoad(url, HintOrigin::NAVIGATION);
-  predictor_->CancelPageLoadHint(url);
-  histogram_tester.ExpectTotalCount(
-      internal::kResourcePrefetchPredictorPrefetchingDurationHistogram, 1);
-
-  // Mismatched start / end.
-  predictor_->PrepareForPageLoad(url, HintOrigin::NAVIGATION);
-  predictor_->CancelPageLoadHint(url2);
-  // No increment.
-  histogram_tester.ExpectTotalCount(
-      internal::kResourcePrefetchPredictorPrefetchingDurationHistogram, 1);
-
-  // Can track a navigation (url2) while one is still in progress (url).
-  predictor_->PrepareForPageLoad(url2, HintOrigin::NAVIGATION);
-  predictor_->CancelPageLoadHint(url2);
-  histogram_tester.ExpectTotalCount(
-      internal::kResourcePrefetchPredictorPrefetchingDurationHistogram, 2);
-
-  // Do not track non-prefetchable URLs.
-  predictor_->PrepareForPageLoad(url3, HintOrigin::NAVIGATION);
-  predictor_->CancelPageLoadHint(url3);
-  // No increment.
-  histogram_tester.ExpectTotalCount(
-      internal::kResourcePrefetchPredictorPrefetchingDurationHistogram, 2);
-}
-
 TEST_F(LoadingPredictorTest, TestMainFrameResponseCancelsHint) {
   const GURL url = GURL(kUrl);
   predictor_->PrepareForPageLoad(url, HintOrigin::EXTERNAL);

chrome/browser/predictors/resource_prefetch_predictor.cc

@@ -34,13 +34,6 @@ namespace {
 const float kMinOriginConfidenceToTriggerPreconnect = 0.75f;
 const float kMinOriginConfidenceToTriggerPreresolve = 0.2f;
 
-// For reporting events of interest that are not tied to any navigation.
-enum ReportingEvent {
-  REPORTING_EVENT_ALL_HISTORY_CLEARED = 0,
-  REPORTING_EVENT_PARTIAL_HISTORY_CLEARED = 1,
-  REPORTING_EVENT_COUNT = 2
-};
-
 float ComputeRedirectConfidence(const predictors::RedirectStat& redirect) {
   return (redirect.number_of_hits() + 0.0) /
          (redirect.number_of_hits() + redirect.number_of_misses());
@@ -438,17 +431,10 @@ void ResourcePrefetchPredictor::OnURLsDeleted(
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   DCHECK(initialization_state_ == INITIALIZED);
 
-  if (deletion_info.IsAllHistory()) {
+  if (deletion_info.IsAllHistory())
     DeleteAllUrls();
-    UMA_HISTOGRAM_ENUMERATION("ResourcePrefetchPredictor.ReportingEvent",
-                              REPORTING_EVENT_ALL_HISTORY_CLEARED,
-                              REPORTING_EVENT_COUNT);
-  } else {
+  else
     DeleteUrls(deletion_info.deleted_rows());
-    UMA_HISTOGRAM_ENUMERATION("ResourcePrefetchPredictor.ReportingEvent",
-                              REPORTING_EVENT_PARTIAL_HISTORY_CLEARED,
-                              REPORTING_EVENT_COUNT);
-  }
 }
 
 void ResourcePrefetchPredictor::OnHistoryServiceLoaded(

chrome/browser/predictors/resource_prefetch_predictor.h

@@ -39,9 +39,6 @@ struct OriginRequestSummary;
 struct PageRequestSummary;
 
 namespace internal {
-constexpr char kResourcePrefetchPredictorPrefetchingDurationHistogram[] =
-    "ResourcePrefetchPredictor.PrefetchingDuration";
-
 struct LastVisitTimeCompare {
   template <typename T>
   bool operator()(const T& lhs, const T& rhs) const {

tools/metrics/histograms/histograms.xml

@@ -90743,6 +90743,9 @@ uploading your change for review.
 </histogram>
 
 <histogram name="ResourcePrefetchPredictor.PrefetchingDuration" units="ms">
+  <obsolete>
+    Deprecated at M72. No longer recorded.
+  </obsolete>
   <owner>alexilin@chromium.org</owner>
   <summary>
     Amount of time available for prefetching. Specifically, this is a time
@@ -90804,6 +90807,9 @@ uploading your change for review.
 
 <histogram name="ResourcePrefetchPredictor.ReportingEvent"
     enum="ResourcePrefetchPredictorReportingEvent">
+  <obsolete>
+    Deprecated at M72. No longer recorded.
+  </obsolete>
   <owner>alexilin@chromium.org</owner>
   <summary>
     Records stats about various interesting events such as - when partial or all