[NTP::SectionOrder] Add category position metric for opened suggestions.

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 4f61eed1fa9af77c9dbb0f6ea8386caaae14bbf1..87f40998e4a1d3e3f6de8af2bc65af55331475d2 100644
--- a/components/ntp_snippets/content_suggestions_metrics.cc
+++ b/components/ntp_snippets/content_suggestions_metrics.cc
@@ -20,6 +20,7 @@ namespace {
 
 const int kMaxSuggestionsPerCategory = 10;

[finkm, 2017/01/05 16:31:29]

Hmmm ... since we have the more button, a section can have more then 10
suggestions. How does UMA_HISTOGRAM_ENUMERATION(name, sample, enum_max) behave
if sample > enum_max?

[vitaliii, 2017/01/05 17:02:46]

I created a bug and added a TODO (as per our offline discussion).

 const int kMaxSuggestionsTotal = 50;

[finkm, 2017/01/05 16:31:29]

same as above

[vitaliii, 2017/01/05 17:02:46]

same as above.

+const int kMaxCategories = 10;
 
 const char kHistogramCountOnNtpOpened[] =
     "NewTabPage.ContentSuggestions.CountOnNtpOpened";
@@ -28,6 +29,8 @@ const char kHistogramShownAge[] = "NewTabPage.ContentSuggestions.ShownAge";
 const char kHistogramShownScore[] = "NewTabPage.ContentSuggestions.ShownScore";
 const char kHistogramOpened[] = "NewTabPage.ContentSuggestions.Opened";
 const char kHistogramOpenedAge[] = "NewTabPage.ContentSuggestions.OpenedAge";
+const char kHistogramOpenedCategoryPosition[] =
+    "NewTabPage.ContentSuggestions.OpenedCategoryPosition";
 const char kHistogramOpenedScore[] =
     "NewTabPage.ContentSuggestions.OpenedScore";
 const char kHistogramOpenDisposition[] =
@@ -231,6 +234,16 @@ void RecordContentSuggestionsUsage() {
       base::UserMetricsAction("NewTabPage_ContentSuggestions_ArticlesUsage"));
 }
 
+int GetCategoryPosition(
+    Category category,
+    const ntp_snippets::ContentSuggestionsService* service) {
+  std::vector<Category> ordered_categories = service->GetCategories();
+  DCHECK(base::ContainsValue(ordered_categories, category));
+  auto it =
+      std::find(ordered_categories.begin(), ordered_categories.end(), category);
+  return it - ordered_categories.begin();
+}
+
 }  // namespace
 
 void OnPageShown(
@@ -248,13 +261,14 @@ void OnPageShown(
 
 void OnSuggestionShown(int global_position,
                        Category category,
-                       int category_position,
+                       int position_in_category,
                        base::Time publish_date,
                        base::Time last_background_fetch_time,
                        float score) {
   UMA_HISTOGRAM_ENUMERATION(kHistogramShown, global_position,
                             kMaxSuggestionsTotal);
-  LogCategoryHistogramEnumeration(kHistogramShown, category, category_position,
+  LogCategoryHistogramEnumeration(kHistogramShown, category,
+                                  position_in_category,
                                   kMaxSuggestionsPerCategory);
 
   base::TimeDelta age = base::Time::Now() - publish_date;
@@ -267,7 +281,7 @@ void OnSuggestionShown(int global_position,
   // 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) {
+      position_in_category == 0) {
     RecordContentSuggestionsUsage();
 
     // Records the time since the last background fetch of the remote content
@@ -280,15 +294,23 @@ void OnSuggestionShown(int global_position,
   }
 }
 
-void OnSuggestionOpened(int global_position,
+void OnSuggestionOpened(const ContentSuggestionsService* service,
+                        int global_position,
                         Category category,
-                        int category_position,
+                        int position_in_category,
                         base::Time publish_date,
                         float score,
                         WindowOpenDisposition disposition) {
+  const int category_position = GetCategoryPosition(category, service);
+  UMA_HISTOGRAM_ENUMERATION(kHistogramOpenedCategoryPosition, category_position,
+                            kMaxCategories);
+  LogCategoryHistogramEnumeration(kHistogramOpenedCategoryPosition, category,
+                                  category_position, kMaxCategories);
+
   UMA_HISTOGRAM_ENUMERATION(kHistogramOpened, global_position,
                             kMaxSuggestionsTotal);
-  LogCategoryHistogramEnumeration(kHistogramOpened, category, category_position,
+  LogCategoryHistogramEnumeration(kHistogramOpened, category,
+                                  position_in_category,
                                   kMaxSuggestionsPerCategory);
 
   base::TimeDelta age = base::Time::Now() - publish_date;
@@ -310,13 +332,13 @@ void OnSuggestionOpened(int global_position,
 
 void OnSuggestionMenuOpened(int global_position,
                             Category category,
-                            int category_position,
+                            int position_in_category,
                             base::Time publish_date,
                             float score) {
   UMA_HISTOGRAM_ENUMERATION(kHistogramMenuOpened, global_position,
                             kMaxSuggestionsTotal);
   LogCategoryHistogramEnumeration(kHistogramMenuOpened, category,
-                                  category_position,
+                                  position_in_category,
                                   kMaxSuggestionsPerCategory);
 
   base::TimeDelta age = base::Time::Now() - publish_date;
@@ -327,19 +349,19 @@ void OnSuggestionMenuOpened(int global_position,
 
 void OnSuggestionDismissed(int global_position,
                            Category category,
-                           int category_position,
+                           int position_in_category,
                            bool visited) {
   if (visited) {
     UMA_HISTOGRAM_ENUMERATION(kHistogramDismissedVisited, global_position,
                               kMaxSuggestionsTotal);
     LogCategoryHistogramEnumeration(kHistogramDismissedVisited, category,
-                                    category_position,
+                                    position_in_category,
                                     kMaxSuggestionsPerCategory);
   } else {
     UMA_HISTOGRAM_ENUMERATION(kHistogramDismissedUnvisited, global_position,
                               kMaxSuggestionsTotal);
     LogCategoryHistogramEnumeration(kHistogramDismissedUnvisited, category,
-                                    category_position,
+                                    position_in_category,
                                     kMaxSuggestionsPerCategory);
   }
 }