Move Indexed DB from dedicated thread to task scheduler

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/weak_ptr.h"
-#include "base/threading/thread_checker.h"
+#include "base/sequence_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 IndexedDBContextImpl;
 class IndexedDBDatabaseError;
 class IndexedDBTransaction;
 
-// Expected to be constructed on IO thread and called/deleted from IDB thread.
+// Expected to be constructed on IO thread and called/deleted from IDB sequence.
 class CONTENT_EXPORT IndexedDBDatabaseCallbacks
     : public base::RefCounted<IndexedDBDatabaseCallbacks> {
  public:
   IndexedDBDatabaseCallbacks(
       scoped_refptr<IndexedDBContextImpl> context,
       ::indexed_db::mojom::DatabaseCallbacksAssociatedPtrInfo callbacks_info);
 
   virtual void OnForcedClose();
   virtual void OnVersionChange(int64_t old_version, int64_t new_version);
 
   virtual void OnAbort(const IndexedDBTransaction& transaction,
                        const IndexedDBDatabaseError& error);
   virtual void OnComplete(const IndexedDBTransaction& transaction);
   virtual void OnDatabaseChange(
       ::indexed_db::mojom::ObserverChangesPtr changes);
 
  protected:
   virtual ~IndexedDBDatabaseCallbacks();
 
  private:
   friend class base::RefCounted<IndexedDBDatabaseCallbacks>;
 
   class IOThreadHelper;
 
   bool complete_ = false;
   scoped_refptr<IndexedDBContextImpl> indexed_db_context_;
   std::unique_ptr<IOThreadHelper, BrowserThread::DeleteOnIOThread> io_helper_;
-  base::ThreadChecker thread_checker_;
+  SEQUENCE_CHECKER(sequence_checker_);
 
   DISALLOW_COPY_AND_ASSIGN(IndexedDBDatabaseCallbacks);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_DATABASE_CALLBACKS_H_