[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..b95c0de2b1b771ce0e27264c62839cf085b61730 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;
 const int kMaxSuggestionsTotal = 50;
+const int kMaxCategories = 20;

[Marc Treib, 2017/01/16 10:45:42]

This seems a bit excessive - I don't think we'll ever have more than 10
categories at any time?

[vitaliii, 2017/01/18 09:19:20]

Is there any downside of overestimating it?
We may have per topic categories and then 20 won't be that many.

[Marc Treib, 2017/01/18 09:30:04]

Well, the histogram will use more memory, probably more bandwidth when
transmitting it, etc. It's not a huge deal, but IMO in practice we'll just have
lots of empty buckets. With topic categories, there could easily *exist* more
than 10, but I don't think we'd ever show more than 10 *at the same time*.

[vitaliii, 2017/01/18 09:36:30]

Done, 10 now.

 
 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 kHistogramOpenedCategoryRank[] =
+    "NewTabPage.ContentSuggestions.OpenedCategoryRank";
 const char kHistogramOpenedScore[] =
     "NewTabPage.ContentSuggestions.OpenedScore";
 const char kHistogramOpenDisposition[] =
@@ -248,13 +251,14 @@ 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 +271,7 @@ 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
@@ -282,13 +286,20 @@ void OnSuggestionShown(int global_position,
 
 void OnSuggestionOpened(int global_position,
                         Category category,
-                        int category_position,
+                        int category_rank,
+                        int position_in_category,
                         base::Time publish_date,
                         float score,
                         WindowOpenDisposition disposition) {
+  UMA_HISTOGRAM_ENUMERATION(kHistogramOpenedCategoryRank, category_rank,
+                            kMaxCategories);
+  LogCategoryHistogramEnumeration(kHistogramOpenedCategoryRank, category,
+                                  category_rank, 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 +321,13 @@ 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 +338,19 @@ 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);
   }
 }