Stackable file_util for FileAPIs. Sample code for discussion. Incomplete. Cannot be compiled.

webkit/fileapi/quota_file_util.h

+// Copyright (c) 2011 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_FILEAPI_QUOTA_FILE_UTIL_H_
+#define WEBKIT_FILEAPI_QUOTA_FILE_UTIL_H_
+
+namespace fileapi {
+
+class QuotaFileUtil : public FileSystemFileUtilBase {
+ public:
+  static QuotaFileUtil* GetInstance();
+  virtual ~QuotaFileUtil() {}
+
+  base::PlatformFileError Copy(
+      const FileSystemOperationContext& fs_context,
+      const FilePath& src_file_path,
+      const FilePath& dest_file_path);
+
+ protected:
+  QuotaFileUtil() {}
+
+ private:
+  friend struct DefaultSingletonTraits<QuotaFileUtilBase>;
+  DISALLOW_COPY_AND_ASSIGN(QuotaFileUtil);
+
+  FileSystemFileUtilBase* next_file_util_to_quota;
+};
+
+}  // namespace fileapi
+
+#endif  // WEBKIT_FILEAPI_QUOTA_FILE_UTIL_H_