[NTP Snippets] Cleanups from clang-tidy

components/ntp_snippets/ntp_snippets_database.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/ntp_snippets_database.h"
 
 #include <utility>
 
 #include "base/files/file_path.h"
 #include "components/leveldb_proto/proto_database_impl.h"
@@ skipping 29 matching lines @@
   database_->Init(kDatabaseUMAClientName, snippet_dir,
                   base::Bind(&NTPSnippetsDatabase::OnDatabaseInited,
                              weak_ptr_factory_.GetWeakPtr()));
 
   base::FilePath image_dir = database_dir.AppendASCII(kImageDatabaseFolder);
   image_database_->Init(kImageDatabaseUMAClientName, image_dir,
                         base::Bind(&NTPSnippetsDatabase::OnImageDatabaseInited,
                                    weak_ptr_factory_.GetWeakPtr()));
 }
 
-NTPSnippetsDatabase::~NTPSnippetsDatabase() {}
+NTPSnippetsDatabase::~NTPSnippetsDatabase() = default;
 
 bool NTPSnippetsDatabase::IsInitialized() const {
   return !IsErrorState() && database_initialized_ &&
       image_database_initialized_;
 }
 
 bool NTPSnippetsDatabase::IsErrorState() const {
   return !database_ || !image_database_;
 }
 
@@ skipping 223 matching lines @@
     std::unique_ptr<std::vector<std::string>> keys_to_remove) {
   DCHECK(IsInitialized());
 
   image_database_->UpdateEntries(
       base::MakeUnique<ImageKeyEntryVector>(), std::move(keys_to_remove),
       base::Bind(&NTPSnippetsDatabase::OnImageDatabaseSaved,
                  weak_ptr_factory_.GetWeakPtr()));
 }
 
 }  // namespace ntp_snippets