Replace deprecated base::NonThreadSafe in content/browser/appcache in favor of SequenceChecker.

content/browser/appcache/appcache_request.cc

 // Copyright (c) 2017 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 "content/browser/appcache/appcache_request.h"
 #include "content/common/appcache_interfaces.h"
 #include "net/url_request/url_request.h"
 
 namespace content {
 
+AppCacheRequest::~AppCacheRequest() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+}
+
 // static
 bool AppCacheRequest::IsSchemeAndMethodSupportedForAppCache(
     const AppCacheRequest* request) {
   return IsSchemeSupportedForAppCache(request->GetURL()) &&
          IsMethodSupportedForAppCache(request->GetMethod());
 }
 
 net::URLRequest* AppCacheRequest::GetURLRequest() {
   return nullptr;
 }
 
 ResourceRequest* AppCacheRequest::GetResourceRequest() {
   return nullptr;
 }
 
 }  // namespace content