Prevent cross-thread refcounting for thread-unsafe IndexedDBCallbacks.

content/browser/indexed_db/indexed_db_database_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_DATABASE_CALLBACKS_H_
 #define CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_DATABASE_CALLBACKS_H_
 
 #include <stdint.h>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "base/threading/thread_checker.h"
 #include "content/common/content_export.h"
 #include "content/common/indexed_db/indexed_db.mojom.h"
 #include "content/public/browser/browser_thread.h"
 
 namespace content {
 class IndexedDBDatabaseError;
 class IndexedDBDispatcherHost;
 class IndexedDBObserverChanges;
 
 class CONTENT_EXPORT IndexedDBDatabaseCallbacks
@@ skipping 18 matching lines @@
   virtual ~IndexedDBDatabaseCallbacks();
 
  private:
   friend class base::RefCounted<IndexedDBDatabaseCallbacks>;
 
   class IOThreadHelper;
 
   scoped_refptr<IndexedDBDispatcherHost> dispatcher_host_;
   int32_t ipc_thread_id_;
   std::unique_ptr<IOThreadHelper, BrowserThread::DeleteOnIOThread> io_helper_;
+  base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(IndexedDBDatabaseCallbacks);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_DATABASE_CALLBACKS_H_