Add ClearHistory() to ContentSuggestionsService and its providers

components/ntp_snippets/bookmarks/bookmark_suggestions_provider.cc

Index: components/ntp_snippets/bookmarks/bookmark_suggestions_provider.cc
diff --git a/components/ntp_snippets/bookmarks/bookmark_suggestions_provider.cc b/components/ntp_snippets/bookmarks/bookmark_suggestions_provider.cc
index 8919f16619aa1c61d297cb9eefb087c4b045122b..6a6f5b6787976694833b01c06067dfb1ad2626e3 100644
--- a/components/ntp_snippets/bookmarks/bookmark_suggestions_provider.cc
+++ b/components/ntp_snippets/bookmarks/bookmark_suggestions_provider.cc
@@ -184,6 +184,11 @@ void BookmarkSuggestionsProvider::FetchSuggestionImage(
       FROM_HERE, base::Bind(callback, suggestion_id, gfx::Image()));
 }
 
+void BookmarkSuggestionsProvider::ClearHistory(base::Time begin,
+                                               base::Time end) {
+  // TODO(vitaliii): Implement. See crbug.com/640972.
+}
+
 void BookmarkSuggestionsProvider::ClearCachedSuggestions(Category category) {
   DCHECK_EQ(category, provided_category_);
   // Ignored.