Let IndexedDBContextImpl create its own task runner

content/browser/indexed_db/indexed_db_dispatcher_host.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_DISPATCHER_HOST_H_
 #define CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_DISPATCHER_HOST_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 91 matching lines @@
             int64_t version,
             int64_t transaction_id) override;
   void DeleteDatabase(
       ::indexed_db::mojom::CallbacksAssociatedPtrInfo callbacks_info,
       const url::Origin& origin,
       const base::string16& name,
       bool force_close) override;
 
   void InvalidateWeakPtrsAndClearBindings();
 
+  base::SequencedTaskRunner* IDBTaskRunner() const;
+
   scoped_refptr<IndexedDBContextImpl> indexed_db_context_;
   scoped_refptr<ChromeBlobStorageContext> blob_storage_context_;
-  scoped_refptr<base::SequencedTaskRunner> idb_runner_;
 
   // Maps blob uuid to a pair (handle, ref count). Entry is added and/or count
   // is incremented in HoldBlobData(), and count is decremented and/or entry
   // removed in DropBlobData().
   std::map<std::string,
            std::pair<std::unique_ptr<storage::BlobDataHandle>, int>>
       blob_data_handle_map_;
 
   // Used to set file permissions for blob storage.
   const int ipc_process_id_;
 
   mojo::AssociatedBindingSet<::indexed_db::mojom::Factory> bindings_;
 
   mojo::StrongAssociatedBindingSet<::indexed_db::mojom::Database>
       database_bindings_;
 
   mojo::StrongAssociatedBindingSet<::indexed_db::mojom::Cursor>
       cursor_bindings_;
 
   IDBSequenceHelper* idb_helper_;
 
   base::WeakPtrFactory<IndexedDBDispatcherHost> weak_factory_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(IndexedDBDispatcherHost);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_DISPATCHER_HOST_H_