Add ClearHistory() to ContentSuggestionsService and its providers

components/ntp_snippets/offline_pages/offline_page_suggestions_provider.cc

Index: components/ntp_snippets/offline_pages/offline_page_suggestions_provider.cc
diff --git a/components/ntp_snippets/offline_pages/offline_page_suggestions_provider.cc b/components/ntp_snippets/offline_pages/offline_page_suggestions_provider.cc
index 79675d4062de68b7ae7b3e11eb01370ebea09b5c..dd2ed1052b50d5aaea72cb5a11424bda1c85846f 100644
--- a/components/ntp_snippets/offline_pages/offline_page_suggestions_provider.cc
+++ b/components/ntp_snippets/offline_pages/offline_page_suggestions_provider.cc
@@ -150,6 +150,13 @@ void OfflinePageSuggestionsProvider::FetchSuggestionImage(
       FROM_HERE, base::Bind(callback, gfx::Image()));
 }
 
+void OfflinePageSuggestionsProvider::ClearHistory(
+    base::Time begin,
+    base::Time end,
+    const base::Callback<bool(const GURL& url)>& filter) {
+  // TODO(vitaliii): Implement. See crbug.com/641321.
+}
+
 void OfflinePageSuggestionsProvider::ClearCachedSuggestions(Category category) {
   // Ignored.
 }