Add a new histogram for EngagementScore to check whether it's zero

chrome/browser/engagement/site_engagement_metrics.cc

 // Copyright 2015 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 "chrome/browser/engagement/site_engagement_metrics.h"
 
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/string_number_conversions.h"
+#include "chrome/browser/engagement/site_engagement_score.h"
 
 namespace {
 
 // These numbers are used as suffixes for the
 // SiteEngagementService.EngagementScoreBucket_* histogram. If these bases
 // change, the EngagementScoreBuckets suffix in histograms.xml should be
 // updated.
 const int kEngagementBucketHistogramBuckets[] = {0,  10, 20, 30, 40, 50,
                                                  60, 70, 80, 90, 100};
 
@@ skipping 16 matching lines @@
 
 const char SiteEngagementMetrics::kEngagementScoreHistogram[] =
     "SiteEngagementService.EngagementScore";
 
 const char SiteEngagementMetrics::kEngagementScoreHistogramHTTP[] =
     "SiteEngagementService.EngagementScore.HTTP";
 
 const char SiteEngagementMetrics::kEngagementScoreHistogramHTTPS[] =
     "SiteEngagementService.EngagementScore.HTTPS";
 
+const char SiteEngagementMetrics::kEngagementScoreHistogramZero[] =
+    "SiteEngagementService.EngagementScore.Zero";
+
 const char SiteEngagementMetrics::kOriginsWithMaxEngagementHistogram[] =
     "SiteEngagementService.OriginsWithMaxEngagement";
 
 const char SiteEngagementMetrics::kOriginsWithMaxDailyEngagementHistogram[] =
     "SiteEngagementService.OriginsWithMaxDailyEngagement";
 
 const char SiteEngagementMetrics::kPercentOriginsWithMaxEngagementHistogram[] =
     "SiteEngagementService.PercentOriginsWithMaxEngagement";
 
 const char SiteEngagementMetrics::kEngagementTypeHistogram[] =
@@ skipping 33 matching lines @@
     return;
 
   // Total up all HTTP and HTTPS engagement so we can log the percentage of
   // engagement to HTTPS origins.
   double total_http_https_engagement = 0;
   double https_engagement = 0;
   std::map<int, int> score_buckets;
   for (size_t i = 0; i < arraysize(kEngagementBucketHistogramBuckets); ++i)
     score_buckets[kEngagementBucketHistogramBuckets[i]] = 0;
 
+  const double threshold_0 = SiteEngagementScore::GetScoreCleanupThreshold();
   for (const auto& value : score_map) {
     double score = value.second;
     UMA_HISTOGRAM_COUNTS_100(kEngagementScoreHistogram, score);
+    UMA_HISTOGRAM_BOOLEAN(kEngagementScoreHistogramZero, score < threshold_0);
     if (value.first.SchemeIs(url::kHttpsScheme)) {
       UMA_HISTOGRAM_COUNTS_100(kEngagementScoreHistogramHTTPS, score);
       https_engagement += score;
       total_http_https_engagement += score;
     } else if (value.first.SchemeIs(url::kHttpScheme)) {
       UMA_HISTOGRAM_COUNTS_100(kEngagementScoreHistogramHTTP, score);
       total_http_https_engagement += score;
     }
 
     auto bucket = score_buckets.lower_bound(score);
@@ skipping 56 matching lines @@
 SiteEngagementMetrics::GetEngagementBucketHistogramNames() {
   std::vector<std::string> histogram_names;
   for (size_t i = 0; i < arraysize(kEngagementBucketHistogramBuckets); ++i) {
     histogram_names.push_back(
         kEngagementBucketHistogramBase +
         base::IntToString(kEngagementBucketHistogramBuckets[i]));
   }
 
   return histogram_names;
 }