Add ClearHistory() to ContentSuggestionsService and its providers

components/ntp_snippets/offline_pages/offline_page_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_OFFLINE_PAGE_SUGGESTIONS_PROVIDER_H_
 #define COMPONENTS_NTP_SNIPPETS_OFFLINE_PAGES_OFFLINE_PAGE_SUGGESTIONS_PROVIDER_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 35 matching lines @@
 
   static void RegisterProfilePrefs(PrefRegistrySimple* registry);
 
  private:
   // ContentSuggestionsProvider implementation.
   CategoryStatus GetCategoryStatus(Category category) override;
   CategoryInfo GetCategoryInfo(Category category) override;
   void DismissSuggestion(const std::string& suggestion_id) override;
   void FetchSuggestionImage(const std::string& suggestion_id,
                             const ImageFetchedCallback& callback) override;
+  void ClearHistory(base::Time begin, base::Time end) override;
   void ClearCachedSuggestions(Category category) override;
   void GetDismissedSuggestionsForDebugging(
       Category category,
       const DismissedSuggestionsCallback& callback) override;
   void ClearDismissedSuggestionsForDebugging(Category category) override;
 
   // OfflinePageModel::Observer implementation.
   void OfflinePageModelLoaded(offline_pages::OfflinePageModel* model) override;
   void OfflinePageModelChanged(offline_pages::OfflinePageModel* model) override;
   void OfflinePageDeleted(int64_t offline_id,
@@ skipping 56 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_;
 
   DISALLOW_COPY_AND_ASSIGN(OfflinePageSuggestionsProvider);
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_OFFLINE_PAGES_OFFLINE_PAGE_SUGGESTIONS_PROVIDER_H_