DomStorageArea -> DomStorageDatabase indirection; add *StorageDatabaseAdapter.

webkit/dom_storage/dom_storage_database_adapter.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 WEBKIT_DOM_STORAGE_DOM_STORAGE_DATABASE_ADAPTER_H_
+#define WEBKIT_DOM_STORAGE_DOM_STORAGE_DATABASE_ADAPTER_H_
+#pragma once
+
+// Database interface used by DomStorageArea. Abstracts the differences between
+// the per-origin DomStorageDatabases for localStorage and
+// SessionStorageDatabase which stores multiple origins.
+
+#include "webkit/dom_storage/dom_storage_types.h"
+
+namespace dom_storage {
+
+class DomStorageDatabaseAdapter {
+ public:
+  virtual ~DomStorageDatabaseAdapter() {}
+  virtual void ReadAllValues(ValuesMap* result) = 0;
+  virtual bool CommitChanges(
+      bool clear_all_first, const ValuesMap& changes) = 0;
+  virtual void DeleteFiles() {}
+  virtual void Reset() {}
+};
+
+}  // namespace dom_storage
+
+#endif  // WEBKIT_DOM_STORAGE_DOM_STORAGE_DATABASE_ADAPTER_H_