[NTP::SectionOrder] Track category index after it has been moved up.

components/ntp_snippets/content_suggestions_metrics.cc

 // Copyright 2016 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 "components/ntp_snippets/content_suggestions_metrics.h"
 
 #include <cmath>
 #include <string>
 #include <type_traits>
 
@@ skipping 37 matching lines @@
 const char kHistogramDismissedVisited[] =
     "NewTabPage.ContentSuggestions.DismissedVisited";
 const char kHistogramArticlesUsageTimeLocal[] =
     "NewTabPage.ContentSuggestions.UsageTimeLocal";
 const char kHistogramVisitDuration[] =
     "NewTabPage.ContentSuggestions.VisitDuration";
 const char kHistogramMoreButtonShown[] =
     "NewTabPage.ContentSuggestions.MoreButtonShown";
 const char kHistogramMoreButtonClicked[] =
     "NewTabPage.ContentSuggestions.MoreButtonClicked";
+const char kHistogramMovedUpCategoryNewIndex[] =
+    "NewTabPage.ContentSuggestions.MovedUpCategoryNewIndex";
 const char kHistogramCategoryDismissed[] =
     "NewTabPage.ContentSuggestions.CategoryDismissed";
 const char kHistogramContentSuggestionsTimeSinceLastBackgroundFetch[] =
     "NewTabPage.ContentSuggestions.TimeSinceLastBackgroundFetch";
 
 const char kPerCategoryHistogramFormat[] = "%s.%s";
 
 // This mostly corresponds to the KnownCategories enum, but it is contiguous
 // and contains exactly the values to be recorded in UMA. Don't remove or
 // reorder elements, only add new ones at the end (before COUNT), and keep in
@@ skipping 255 matching lines @@
                                  kMaxSuggestionsPerCategory);
   }
 }
 
 void OnSuggestionTargetVisited(Category category, base::TimeDelta visit_time) {
   std::string name =
       GetCategoryHistogramName(kHistogramVisitDuration, category);
   base::UmaHistogramLongTimes(name, visit_time);
 }
 
+void OnCategoryMovedUp(int new_index) {
+  UMA_HISTOGRAM_EXACT_LINEAR(kHistogramMovedUpCategoryNewIndex, new_index,
+                             kMaxCategories);
+}
+
 void OnMoreButtonShown(Category category, int position) {
   // The "more" card can appear in addition to the actual suggestions, so add
   // one extra bucket to this histogram.
   LogCategoryHistogramPosition(kHistogramMoreButtonShown, category, position,
                                kMaxSuggestionsPerCategory + 1);
 }
 
 void OnMoreButtonClicked(Category category, int position) {
   // The "more" card can appear in addition to the actual suggestions, so add
   // one extra bucket to this histogram.
   LogCategoryHistogramPosition(kHistogramMoreButtonClicked, category, position,
                                kMaxSuggestionsPerCategory + 1);
 }
 
 void OnCategoryDismissed(Category category) {
   UMA_HISTOGRAM_ENUMERATION(kHistogramCategoryDismissed,
                             GetHistogramCategory(category),
                             HistogramCategories::COUNT);
 }
 
 }  // namespace metrics
 }  // namespace ntp_snippets