[NTP::SectionOrder] Make ClickBasedRanker move dismissed sections down.

components/ntp_snippets/category_rankers/category_ranker.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_CATEGORY_RANKERS_CATEGORY_RANKER_H_
 #define COMPONENTS_NTP_SNIPPETS_CATEGORY_RANKERS_CATEGORY_RANKER_H_
 
 #include "base/time/time.h"
 #include "components/ntp_snippets/category.h"
 
@@ skipping 18 matching lines @@
   virtual void ClearHistory(base::Time begin, base::Time end) = 0;
 
   // If |category| has not been added previously, it is added after all already
   // known categories, otherwise nothing is changed.
   virtual void AppendCategoryIfNecessary(Category category) = 0;
 
   // Feedback data from the user to update the ranking.
 
   // Called whenever a suggestion is opened by the user.
   virtual void OnSuggestionOpened(Category category) = 0;
+
+  // Called whenever a category is dismissed by the user.
+  virtual void OnCategoryDismissed(Category category) = 0;
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_CATEGORY_RANKERS_CATEGORY_RANKER_H_