Add logic for fetching the Reading List entries

components/ntp_snippets/reading_list/reading_list_suggestions_provider.h

 // 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_NTP_SNIPPETS_READING_LIST_READING_LIST_SUGGESTIONS_PROVIDER_H_
 #define COMPONENTS_NTP_SNIPPETS_READING_LIST_READING_LIST_SUGGESTIONS_PROVIDER_H_
 
 #include <set>
 #include <string>
 
+#include "base/scoped_observer.h"
 #include "components/ntp_snippets/callbacks.h"
 #include "components/ntp_snippets/category.h"
 #include "components/ntp_snippets/category_info.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/reading_list/core/reading_list_model_observer.h"
 
 class ReadingListModel;
 
@@ skipping 21 matching lines @@
       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;
 
   // ReadingListModelObserver implementation.
   void ReadingListModelLoaded(const ReadingListModel* model) override;
+  void ReadingListModelBeingDeleted(const ReadingListModel* model) override;
 
  private:
+  // The actual method to fetch Reading List entries. Must be called after the
+  // model is loaded.
   void FetchReadingListInternal();
 
+  // Updates the |category_status_| and notifies the |observer_|, if necessary.
+  void NotifyStatusChanged(CategoryStatus new_status);
   CategoryStatus category_status_;
   const Category provided_category_;
 
   ReadingListModel* reading_list_model_;
+  ScopedObserver<ReadingListModel, ReadingListModelObserver> scoped_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(ReadingListSuggestionsProvider);
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_READING_LIST_READING_LIST_SUGGESTIONS_PROVIDER_H_