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

components/ntp_snippets/content_suggestions_metrics.h

 // 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.
 
 #ifndef COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_METRICS_H_
 #define COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_METRICS_H_
 
 #include <utility>
 #include <vector>
 
@@ skipping 31 matching lines @@
                             base::Time publish_date,
                             float score);
 
 void OnSuggestionDismissed(int global_position,
                            Category category,
                            int position_in_category,
                            bool visited);
 
 void OnSuggestionTargetVisited(Category category, base::TimeDelta visit_time);
 
+void OnCategoryMovedUp(int new_index);
+
 // Should only be called once per NTP for each "more" button.
 void OnMoreButtonShown(Category category, int position);
 
 void OnMoreButtonClicked(Category category, int position);
 
 void OnCategoryDismissed(Category category);
 
 }  // namespace metrics
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_SERVICE_H_