Add a histogram for recording content suggestions local usage time stats.

components/ntp_snippets/content_suggestions_metrics.cc

Index: components/ntp_snippets/content_suggestions_metrics.cc
diff --git a/components/ntp_snippets/content_suggestions_metrics.cc b/components/ntp_snippets/content_suggestions_metrics.cc
index 4117fae096bb855d15ecd5949833e97b1e046919..a19fef36e28515a902349a65dc13b4d65e9b6d1c 100644
--- a/components/ntp_snippets/content_suggestions_metrics.cc
+++ b/components/ntp_snippets/content_suggestions_metrics.cc
@@ -40,6 +40,8 @@ const char kHistogramDismissedUnvisited[] =
     "NewTabPage.ContentSuggestions.DismissedUnvisited";
 const char kHistogramDismissedVisited[] =
     "NewTabPage.ContentSuggestions.DismissedVisited";
+const char kHistogramUsageTimeLocal[] =
+    "NewTabPage.ContentSuggestions.UsageTimeLocal";

[Marc Treib, 2016/11/16 16:14:02]

Maybe .ArticlesUsageTimeLocal since it's for articles only now?

[markusheintz_, 2016/11/16 16:18:36]

Done.

 const char kHistogramVisitDuration[] =
     "NewTabPage.ContentSuggestions.VisitDuration";
 const char kHistogramMoreButtonShown[] =
@@ -159,6 +161,23 @@ void LogCategoryHistogramScore(const char* base_name,
   UmaHistogramScore(name, score);
 }
 
+// Records ContentSuggestions usage. Therefore the day is sliced into 20min
+// buckets. Depending on the current local time the count of the corresponding
+// bucket is increased.
+void RecordContentSuggestionsUsage() {
+  const int kBucketSizeMins = 20;
+  const int kNumBuckets = 24 * 60 / kBucketSizeMins;
+
+  base::Time::Exploded now_exploded;
+  base::Time::Now().LocalExplode(&now_exploded);
+  size_t bucket =
+      (now_exploded.hour * 60 + now_exploded.minute) / kBucketSizeMins;
+
+  UMA_HISTOGRAM_ENUMERATION(kHistogramUsageTimeLocal, bucket, kNumBuckets);
+
+  LOG(ERROR) << " ****************** Zine Usage";

[Marc Treib, 2016/11/16 16:14:02]

Remove this before landing :)

[markusheintz_, 2016/11/16 16:18:36]

Done. sry that line sneaked back in.

+}
+
 }  // namespace
 
 void OnPageShown(
@@ -188,6 +207,13 @@ void OnSuggestionShown(int global_position,
   LogCategoryHistogramAge(kHistogramShownAge, category, age);
 
   LogCategoryHistogramScore(kHistogramShownScore, category, score);
+
+  // When the first of the articles suggestions is shown, then we count this as
+  // a single usage of content suggestions.
+  if (category.IsKnownCategory(KnownCategories::ARTICLES) &&
+      category_position == 0) {
+    RecordContentSuggestionsUsage();
+  }
 }
 
 void OnSuggestionOpened(int global_position,
@@ -212,6 +238,10 @@ void OnSuggestionOpened(int global_position,
   LogCategoryHistogramEnumeration(
       kHistogramOpenDisposition, category, static_cast<int>(disposition),
       static_cast<int>(WindowOpenDisposition::MAX_VALUE) + 1);
+
+  if (category.IsKnownCategory(KnownCategories::ARTICLES)) {
+    RecordContentSuggestionsUsage();
+  }
 }
 
 void OnSuggestionMenuOpened(int global_position,