Prevent cross-thread refcounting for thread-unsafe IndexedDBCallbacks.

content/browser/indexed_db/indexed_db_callbacks.h

 // Copyright (c) 2012 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.
 
 #ifndef CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_CALLBACKS_H_
 #define CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_CALLBACKS_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/strings/string16.h"
+#include "base/threading/thread_checker.h"
 #include "content/browser/indexed_db/indexed_db_database_error.h"
 #include "content/browser/indexed_db/indexed_db_dispatcher_host.h"
 #include "content/common/indexed_db/indexed_db.mojom.h"
 #include "content/common/indexed_db/indexed_db_key.h"
 #include "content/common/indexed_db/indexed_db_key_path.h"
 #include "url/origin.h"
 
 namespace content {
 class IndexedDBBlobInfo;
 class IndexedDBConnection;
@@ skipping 113 matching lines @@
   int32_t ipc_database_id_;
 
   // Used to assert that OnSuccess is only called if there was no data loss.
   blink::WebIDBDataLoss data_loss_;
 
   // The "blocked" event should be sent at most once per request.
   bool sent_blocked_;
   base::TimeTicks connection_open_start_time_;
 
   std::unique_ptr<IOThreadHelper, BrowserThread::DeleteOnIOThread> io_helper_;
+  base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(IndexedDBCallbacks);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_CALLBACKS_H_