Add ClearHistory() to ContentSuggestionsService and its providers

components/ntp_snippets/content_suggestions_service.cc

Index: components/ntp_snippets/content_suggestions_service.cc
diff --git a/components/ntp_snippets/content_suggestions_service.cc b/components/ntp_snippets/content_suggestions_service.cc
index 5a983f423832d440025859ada0dec20eeb99ca3f..7746a03c8b0a79ad6fe3a6a0c401dc9f9e2081a8 100644
--- a/components/ntp_snippets/content_suggestions_service.cc
+++ b/components/ntp_snippets/content_suggestions_service.cc
@@ -81,6 +81,12 @@ void ContentSuggestionsService::FetchSuggestionImage(
                                                          callback);
 }
 
+void ContentSuggestionsService::ClearHistory() {
+  for (const auto& provider : providers_) {
+    provider->ClearHistory();
+  }
+}
+
 void ContentSuggestionsService::ClearAllCachedSuggestions() {
   suggestions_by_category_.clear();
   id_category_map_.clear();