Add Transient FileSystem which goes away after its snapsot file is gone

webkit/fileapi/transient_file_util.h

Index: webkit/fileapi/transient_file_util.h
diff --git a/webkit/fileapi/transient_file_util.h b/webkit/fileapi/transient_file_util.h
new file mode 100644
index 0000000000000000000000000000000000000000..d4d7ab2deb5976f8c1df1e502e97860968559086
--- /dev/null
+++ b/webkit/fileapi/transient_file_util.h
@@ -0,0 +1,36 @@
+// Copyright (c) 2013 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_TRANSIENT_FILE_UTIL_H_
+#define WEBKIT_FILEAPI_TRANSIENT_FILE_UTIL_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "webkit/fileapi/isolated_file_util.h"
+#include "webkit/storage/webkit_storage_export.h"
+
+namespace fileapi {
+
+class FileSystemOperationContext;
+
+class WEBKIT_STORAGE_EXPORT_PRIVATE TransientFileUtil
+    : public IsolatedFileUtil {
+ public:
+  TransientFileUtil() {}
+  virtual ~TransientFileUtil() {}
+
+  // IsolatedFileUtil overrides.
+  virtual webkit_blob::ScopedFile CreateSnapshotFile(
+      FileSystemOperationContext* context,
+      const FileSystemURL& url,
+      base::PlatformFileError* error,
+      base::PlatformFileInfo* file_info,
+      base::FilePath* platform_path) OVERRIDE;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TransientFileUtil);
+};
+
+}  // namespace fileapi
+
+#endif  // WEBKIT_FILEAPI_TRANSIENT_FILE_UTIL_H_