[NTP::Downloads] Limit number of dismissed IDs instead of pruning.

chrome/browser/ntp_snippets/download_suggestions_provider.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 CHROME_BROWSER_NTP_SNIPPETS_DOWNLOAD_SUGGESTIONS_PROVIDER_H_
 #define CHROME_BROWSER_NTP_SNIPPETS_DOWNLOAD_SUGGESTIONS_PROVIDER_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 57 matching lines @@
       const base::Callback<bool(const GURL& url)>& filter) override;
   void ClearCachedSuggestions(ntp_snippets::Category category) override;
   void GetDismissedSuggestionsForDebugging(
       ntp_snippets::Category category,
       const ntp_snippets::DismissedSuggestionsCallback& callback) override;
   void ClearDismissedSuggestionsForDebugging(
       ntp_snippets::Category category) override;
 
   static void RegisterProfilePrefs(PrefRegistrySimple* registry);
 
+  static int GetMaxDismissedCountForTesting();
+
  private:
   friend class DownloadSuggestionsProviderTest;
 
   void GetPagesMatchingQueryCallbackForGetDismissedSuggestions(
       const ntp_snippets::DismissedSuggestionsCallback& callback,
       const std::vector<offline_pages::OfflinePageItem>& offline_pages) const;
 
   // OfflinePageModel::Observer implementation.
   void OfflinePageModelLoaded(offline_pages::OfflinePageModel* model) override;
   void OfflinePageAdded(
@@ skipping 76 matching lines @@
       bool notify,
       const std::vector<offline_pages::OfflinePageItem>&
           all_download_offline_pages);
 
   // Fires the |OnSuggestionInvalidated| event for the suggestion corresponding
   // to the given |id_within_category| and clears it from the dismissed IDs
   // list, if necessary.
   void InvalidateSuggestion(const std::string& id_within_category);
 
   // Reads dismissed IDs related to asset downloads from prefs.
-  std::set<std::string> ReadAssetDismissedIDsFromPrefs() const;
+  std::vector<std::string> ReadAssetDismissedIDsFromPrefs() const;
 
   // Writes |dismissed_ids| into prefs for asset downloads.
   void StoreAssetDismissedIDsToPrefs(
-      const std::set<std::string>& dismissed_ids);
+      const std::vector<std::string>& dismissed_ids);
 
   // Reads dismissed IDs related to offline page downloads from prefs.
   std::set<std::string> ReadOfflinePageDismissedIDsFromPrefs() const;
 
   // Writes |dismissed_ids| into prefs for offline page downloads.
   void StoreOfflinePageDismissedIDsToPrefs(
       const std::set<std::string>& dismissed_ids);
 
-  // Reads from prefs dismissed IDs related to either offline page or asset
-  // downloads (given by |for_offline_page_downloads|).
-  std::set<std::string> ReadDismissedIDsFromPrefs(
-      bool for_offline_page_downloads) const;
+  // Adds a suggestion ID to the dismissed list in prefs, if it is not there.
+  // Works for both Offline Page and Asset downloads.
+  void AddToDismissedStorageIfNeeded(
+      const ntp_snippets::ContentSuggestion::ID& suggestion_id);
 
-  // Writes |dismissed_ids| into prefs for either offline page or asset
-  // downloads (given by |for_offline_page_downloads|).
-  void StoreDismissedIDsToPrefs(bool for_offline_page_downloads,
-                                const std::set<std::string>& dismissed_ids);
+  // Removes a suggestion ID from the dismissed list in prefs, if it is there.
+  // Works for both Offline Page and Asset downloads.
+  void RemoveFromDismissedStorageIfNeeded(
+      const ntp_snippets::ContentSuggestion::ID& suggestion_id);
 
   void UnregisterDownloadItemObservers();
 
   ntp_snippets::CategoryStatus category_status_;
   const ntp_snippets::Category provided_category_;
   offline_pages::OfflinePageModel* offline_page_model_;
   content::DownloadManager* download_manager_;
 
   PrefService* pref_service_;
 
@@ skipping 13 matching lines @@
   // 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_;
 
   base::WeakPtrFactory<DownloadSuggestionsProvider> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadSuggestionsProvider);
 };
 
 #endif  // CHROME_BROWSER_NTP_SNIPPETS_DOWNLOAD_SUGGESTIONS_PROVIDER_H_