Refactor OfflinePageSuggestionsProvider dismissed ID handling

components/ntp_snippets/offline_pages/offline_page_suggestions_provider.h

Index: components/ntp_snippets/offline_pages/offline_page_suggestions_provider.h
diff --git a/components/ntp_snippets/offline_pages/offline_page_suggestions_provider.h b/components/ntp_snippets/offline_pages/offline_page_suggestions_provider.h
index 862ea5df5bf032c8acad706891b47ddd29395e71..bcce11d3f73e2d0059f841ce7186ed903e28dbb7 100644
--- a/components/ntp_snippets/offline_pages/offline_page_suggestions_provider.h
+++ b/components/ntp_snippets/offline_pages/offline_page_suggestions_provider.h
@@ -89,12 +89,21 @@ class OfflinePageSuggestionsProvider
       std::vector<const offline_pages::OfflinePageItem*> offline_page_items)
       const;
 
-  // Reads dismissed IDs from the pref with name |pref_name|.
-  std::set<std::string> ReadDismissedIDsFromPrefs(
-      const std::string& pref_name) const;
+  // If the suggestion for the offline page with the given |offline_id| is
+  // already dismissed, its dismissed flag is removed (as the offline page
+  // doesn't exist anymore), otherwise the |OnSuggestionInvalidated| event is
+  // fired.
+  void InvalidateSuggestion(Category category, int64_t offline_id);
 
-  // Writes |dismissed_ids| to the pref with name |pref_name|.
-  void StoreDismissedIDsToPrefs(const std::string& pref_name,
+  // Gets the preference name for storing the list of dismissed suggestion IDs
+  // for the given |category|.
+  std::string GetDismissedPref(Category category) const;
+
+  // Reads dismissed IDs for the given |category|.
+  std::set<std::string> ReadDismissedIDsFromPrefs(Category category) const;
+
+  // Writes |dismissed_ids| for the given |category|.
+  void StoreDismissedIDsToPrefs(Category category,
                                 const std::set<std::string>& dismissed_ids);
 
   CategoryStatus recent_tabs_status_;
@@ -107,9 +116,6 @@ class OfflinePageSuggestionsProvider
 
   PrefService* pref_service_;
 
-  std::set<std::string> dismissed_recent_tab_ids_;
-  std::set<std::string> dismissed_download_ids_;
-
   // Whether the Download Manager UI is enabled, in which case the More button
   // for the Downloads section can redirect there.
   const bool download_manager_ui_enabled_;