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

components/offline_pages/core/downloads/download_ui_adapter.h

-// Copyright 2016 The Chromium Authors. All rights reserved.
+// Copyright 2017 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_OFFLINE_PAGES_CORE_DOWNLOADS_DOWNLOAD_UI_ADAPTER_H_
 #define COMPONENTS_OFFLINE_PAGES_CORE_DOWNLOADS_DOWNLOAD_UI_ADAPTER_H_
 
 #include <map>
 #include <memory>
 #include <string>
 #include <vector>
@@ skipping 29 matching lines @@
     // Returns true if the page or request with the specified Client Id should
     // be visible in the collection of items exposed by this Adapter. This also
     // indicates if Observers will be notified about changes for the given page.
     virtual bool IsVisibleInUI(const ClientId& client_id) = 0;
     // Sometimes the item should be in the collection but not visible in the UI,
     // temporarily. This is a relatively special case, for example for Last_N
     // snapshots that are only valid while their tab is alive. When the status
     // of temporary visibility changes, the Delegate is supposed to call
     // DownloadUIAdapter::TemporarilyHiddenStatusChanged().
     virtual bool IsTemporarilyHiddenInUI(const ClientId& client_id) = 0;
+
+    // Delegates need a reference to the UI adapter in order to notify it about
+    // visibility changes.
+    virtual void SetUIAdapter(DownloadUIAdapter* ui_adapter) = 0;
   };
 
   // Observer, normally implemented by UI or a Bridge.
   class Observer {
    public:
     // Invoked when UI items are loaded. GetAllItems/GetItem can now be used.
     // Must be listened for in order to start getting the items.
     // If the items are already loaded by the time observer is added, this
     // callback will be posted right away.
     virtual void ItemsLoaded() = 0;
@@ skipping 45 matching lines @@
   // RequestCoordinator::Observer
   void OnAdded(const SavePageRequest& request) override;
   void OnCompleted(const SavePageRequest& request,
                    RequestNotifier::BackgroundSavePageResult status) override;
   void OnChanged(const SavePageRequest& request) override;
 
   // For the DownloadUIAdapter::Delegate, to report the temporary hidden status
   // change.
   void TemporaryHiddenStatusChanged(const ClientId& client_id);
 
+  Delegate* delegate() { return delegate_.get(); }
+
  private:
   enum class State { NOT_LOADED, LOADING_PAGES, LOADING_REQUESTS, LOADED };
 
   struct ItemInfo {
-    explicit ItemInfo(const OfflinePageItem& page);
-    explicit ItemInfo(const SavePageRequest& request);
+    ItemInfo(const OfflinePageItem& page, bool temporarily_hidden);
+    ItemInfo(const SavePageRequest& request, bool temporarily_hidden);
     ~ItemInfo();
 
     std::unique_ptr<DownloadUIItem> ui_item;
 
     // Additional cached data, not exposed to UI through DownloadUIItem.
     // Indicates if this item wraps the completed page or in-progress request.
     bool is_request;
 
     // These are shared between pages and requests.
     int64_t offline_id;
@@ skipping 19 matching lines @@
   void ClearCache();
 
   // Task callbacks.
   void OnOfflinePagesLoaded(const MultipleOfflinePageItemResult& pages);
   void OnRequestsLoaded(std::vector<std::unique_ptr<SavePageRequest>> requests);
 
   void NotifyItemsLoaded(Observer* observer);
   void OnDeletePagesDone(DeletePageResult result);
 
   void AddItemHelper(std::unique_ptr<ItemInfo> item_info);
+  // This function is not re-entrant.  It temporarily sets |deleting_item_|
+  // while it runs, so that functions such as |GetOfflineIdByGuid| will work
+  // during the |ItemDeleted| callback.
   void DeleteItemHelper(const std::string& guid);
 
   // Always valid, this class is a member of the model.
   OfflinePageModel* model_;
 
   // Always valid, a service.
   RequestCoordinator* request_coordinator_;
 
   // A delegate, supplied at construction.
   std::unique_ptr<Delegate> delegate_;
 
   State state_;
 
   // The cache of UI items. The key is DownloadUIItem.guid.
   DownloadUIItems items_;
 
+  std::unique_ptr<ItemInfo> deleting_item_;
+
   // The observers.
   base::ObserverList<Observer> observers_;
   int observers_count_;
 
   base::WeakPtrFactory<DownloadUIAdapter> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadUIAdapter);
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGE_DOWNLOADS_DOWNLOAD_UI_ADAPTER_H_