Only show Last N Pages in the UI when the corresponding tab is visible.

components/ntp_snippets/offline_pages/recent_tab_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 COMPONENTS_NTP_SNIPPETS_OFFLINE_PAGES_RECENT_TAB_SUGGESTIONS_PROVIDER_H_
 #define COMPONENTS_NTP_SNIPPETS_OFFLINE_PAGES_RECENT_TAB_SUGGESTIONS_PROVIDER_H_
 
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/callback_forward.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/time/time.h"
 #include "components/ntp_snippets/category.h"
 #include "components/ntp_snippets/category_status.h"
 #include "components/ntp_snippets/content_suggestion.h"
 #include "components/ntp_snippets/content_suggestions_provider.h"
+#include "components/offline_pages/core/downloads/download_ui_adapter.h"
+#include "components/offline_pages/core/downloads/download_ui_item.h"
 #include "components/offline_pages/core/offline_page_model.h"
 
 class PrefRegistrySimple;
 class PrefService;
 
 namespace ntp_snippets {
 
 // Provides recent tabs content suggestions from the offline pages model.
 class RecentTabSuggestionsProvider
     : public ContentSuggestionsProvider,
-      public offline_pages::OfflinePageModel::Observer {
+      public offline_pages::DownloadUIAdapter::Observer {
  public:
   RecentTabSuggestionsProvider(
       ContentSuggestionsProvider::Observer* observer,
       offline_pages::OfflinePageModel* offline_page_model,
+      offline_pages::RequestCoordinator* request_coordinator,
       PrefService* pref_service);
   ~RecentTabSuggestionsProvider() override;
 
   // ContentSuggestionsProvider implementation.
   CategoryStatus GetCategoryStatus(Category category) override;
   CategoryInfo GetCategoryInfo(Category category) override;
   void DismissSuggestion(const ContentSuggestion::ID& suggestion_id) override;
   void FetchSuggestionImage(const ContentSuggestion::ID& suggestion_id,
                             const ImageFetchedCallback& callback) override;
   void Fetch(const Category& category,
              const std::set<std::string>& known_suggestion_ids,
              const FetchDoneCallback& callback) override;
   void ClearHistory(
       base::Time begin,
       base::Time end,
       const base::Callback<bool(const GURL& url)>& filter) override;
   void ClearCachedSuggestions(Category category) override;
   void GetDismissedSuggestionsForDebugging(
       Category category,
       const DismissedSuggestionsCallback& callback) override;
   void ClearDismissedSuggestionsForDebugging(Category category) override;
 
   static void RegisterProfilePrefs(PrefRegistrySimple* registry);
 
  private:
   friend class RecentTabSuggestionsProviderTest;
 
-  void GetPagesMatchingQueryCallbackForGetDismissedSuggestions(
-      const DismissedSuggestionsCallback& callback,
-      const std::vector<offline_pages::OfflinePageItem>& offline_pages) const;
-
-  // OfflinePageModel::Observer implementation.
-  void OfflinePageModelLoaded(offline_pages::OfflinePageModel* model) override;
-  void OfflinePageAdded(
-      offline_pages::OfflinePageModel* model,
-      const offline_pages::OfflinePageItem& added_page) override;
-  void OfflinePageDeleted(int64_t offline_id,
-                          const offline_pages::ClientId& client_id) override;
+  // DownloadUIAdapter::Observer implementation.
+  void ItemsLoaded() override;
+  void ItemAdded(const offline_pages::DownloadUIItem& ui_item) override;
+  void ItemUpdated(const offline_pages::DownloadUIItem& ui_item) override;
+  void ItemDeleted(const std::string& ui_item_guid) override;
 
   void GetPagesMatchingQueryCallbackForFetchRecentTabs(
       const std::vector<offline_pages::OfflinePageItem>& offline_pages);
 
   // Updates the |category_status_| of the |provided_category_| and notifies the
   // |observer_|, if necessary.
   void NotifyStatusChanged(CategoryStatus new_status);
 
   // Manually requests all offline pages and updates the suggestions.

[vitaliii, 2017/02/15 10:12:15]

s/offline pages/ui utems

[dewittj, 2017/02/15 19:49:45]

Done.

   void FetchRecentTabs();
 
   // Converts an OfflinePageItem to a ContentSuggestion for the

[vitaliii, 2017/02/15 10:12:15]

s/OfflinePageItem/DownloadUIItem

[dewittj, 2017/02/15 19:49:45]

Done.

   // |provided_category_|.
-  ContentSuggestion ConvertOfflinePage(
-      const offline_pages::OfflinePageItem& offline_page) const;
+  ContentSuggestion ConvertUIItem(
+      const offline_pages::DownloadUIItem& ui_item) const;
 
   // Removes duplicates for the same URL leaving only the most recently created
   // items, returns at most |GetMaxSuggestionsCount()| ContentSuggestions
   // corresponding to the remaining items, sorted by creation time (newer
   // first).
   std::vector<ContentSuggestion> GetMostRecentlyCreatedWithoutDuplicates(
-      std::vector<const offline_pages::OfflinePageItem*> offline_page_items)
-      const;
+      std::vector<const offline_pages::DownloadUIItem*> ui_items) const;
 
   // Fires the |OnSuggestionInvalidated| event for the suggestion corresponding
   // to the given |offline_id| and deletes it from the dismissed IDs list, if
   // necessary.
-  void InvalidateSuggestion(int64_t offline_id);
+  void InvalidateSuggestion(const std::string& ui_item_guid);
 
   // Reads dismissed IDs from Prefs.
   std::set<std::string> ReadDismissedIDsFromPrefs() const;
 
   // Writes |dismissed_ids| into Prefs.
   void StoreDismissedIDsToPrefs(const std::set<std::string>& dismissed_ids);
 
   CategoryStatus category_status_;
   const Category provided_category_;
-  offline_pages::OfflinePageModel* offline_page_model_;
+  offline_pages::DownloadUIAdapter* recent_tabs_ui_adapter_;
 
   PrefService* pref_service_;
 
   base::WeakPtrFactory<RecentTabSuggestionsProvider> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RecentTabSuggestionsProvider);
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_OFFLINE_PAGES_RECENT_TAB_SUGGESTIONS_PROVIDER_H_