[NTP Snippets] Cleanups from clang-tidy

components/ntp_snippets/mock_content_suggestions_provider_observer.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/mock_content_suggestions_provider_observer.h"
 
 namespace ntp_snippets {
 
 MockContentSuggestionsProviderObserver::
-    MockContentSuggestionsProviderObserver() {}
+    MockContentSuggestionsProviderObserver() = default;
 
 MockContentSuggestionsProviderObserver::
-    ~MockContentSuggestionsProviderObserver() {}
+    ~MockContentSuggestionsProviderObserver() = default;
 
 void MockContentSuggestionsProviderObserver::OnNewSuggestions(
     ContentSuggestionsProvider* provider,
     Category category,
     std::vector<ContentSuggestion> suggestions) {
   std::list<ContentSuggestion> suggestions_list;
   for (ContentSuggestion& suggestion : suggestions) {
     suggestions_list.push_back(std::move(suggestion));
   }
   OnNewSuggestions(provider, category, suggestions_list);
 }
 
 }  // namespace ntp_snippets