Finalize backend for fetching more NTPSnippets.

components/ntp_snippets/content_suggestions_service.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_CONTENT_SUGGESTIONS_SERVICE_H_
 #define COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_SERVICE_H_
 
 #include <map>
 #include <memory>
 #include <set>
@@ skipping 27 matching lines @@
 // Retrieves suggestions from a number of ContentSuggestionsProviders and serves
 // them grouped into categories. There can be at most one provider per category.
 class ContentSuggestionsService : public KeyedService,
                                   public ContentSuggestionsProvider::Observer,
                                   public history::HistoryServiceObserver {
  public:
   // TODO(treib): All these should probably be OnceCallback.
   using ImageFetchedCallback = base::Callback<void(const gfx::Image&)>;
   using DismissedSuggestionsCallback = base::Callback<void(
       std::vector<ContentSuggestion> dismissed_suggestions)>;
-  using FetchedMoreCallback =
+  using FetchingCallback =
       base::Callback<void(std::vector<ContentSuggestion> suggestions)>;
 
   class Observer {
    public:
     // Fired every time the service receives a new set of data for the given
     // |category|, replacing any previously available data (though in most cases
     // there will be an overlap and only a few changes within the data). The new
     // data is then available through |GetSuggestionsForCategory(category)|.
     virtual void OnNewSuggestions(Category category) = 0;
 
@@ skipping 75 matching lines @@
   // Restores all dismissed categories.
   // This will not trigger an update through the observers.
   void RestoreDismissedCategories();
 
   // Returns whether |category| is dismissed.
   bool IsCategoryDismissed(Category category) const;
 
   // Fetches additional contents for the given |category|. If the fetch was
   // completed, the given |callback| is called with the updated content.
   // This includes new and old data.
-  void FetchMore(const Category& category, const FetchedMoreCallback& callback);
+  void Fetch(const Category& category,
+             std::set<std::string> known_suggestion_ids,
+             const FetchingCallback& callback);
 
   // Observer accessors.
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);
 
   // Registers a new ContentSuggestionsProvider. It must be ensured that at most
   // one provider is registered for every category and that this method is
   // called only once per provider.
   void RegisterProvider(std::unique_ptr<ContentSuggestionsProvider> provider);
 
@@ skipping 146 matching lines @@
   PrefService* pref_service_;
 
   UserClassifier user_classifier_;
 
   DISALLOW_COPY_AND_ASSIGN(ContentSuggestionsService);
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_SERVICE_H_