[NTP Snippets] Cleanups from clang-tidy

components/ntp_snippets/content_suggestions_provider.cc

 // 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.
 
 #include "components/ntp_snippets/content_suggestions_provider.h"
 
 #include "components/ntp_snippets/category_factory.h"
 
 namespace ntp_snippets {
 
 ContentSuggestionsProvider::ContentSuggestionsProvider(
     Observer* observer,
     CategoryFactory* category_factory)
     : observer_(observer), category_factory_(category_factory) {}
 
-ContentSuggestionsProvider::~ContentSuggestionsProvider() {}
+ContentSuggestionsProvider::~ContentSuggestionsProvider() = default;
 
 std::string ContentSuggestionsProvider::MakeUniqueID(
     Category category,
     const std::string& within_category_id) const {
   return category_factory()->MakeUniqueID(category, within_category_id);
 }
 
 Category ContentSuggestionsProvider::GetCategoryFromUniqueID(
     const std::string& unique_id) const {
   return category_factory()->GetCategoryFromUniqueID(unique_id);
 }
 
 std::string ContentSuggestionsProvider::GetWithinCategoryIDFromUniqueID(
     const std::string& unique_id) const {
   return category_factory()->GetWithinCategoryIDFromUniqueID(unique_id);
 }
 
 }  // namespace ntp_snippets