Implement async verision of FileSystemFileUtil and in-memory file system for testing purposes.

webkit/chromeos/fileapi/async_file_stream.h

Index: webkit/chromeos/fileapi/async_file_stream.h
diff --git a/webkit/chromeos/fileapi/async_file_stream.h b/webkit/chromeos/fileapi/async_file_stream.h
new file mode 100644
index 0000000000000000000000000000000000000000..141f9ed3c1a7c859f0179c406f83c6874f1174f5
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+++ b/webkit/chromeos/fileapi/async_file_stream.h
@@ -0,0 +1,38 @@
+// 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_CHROMEOS_FILEAPI_ASYNC_FILE_STREAM_H_
+#define WEBKIT_CHROMEOS_FILEAPI_ASYNC_FILE_STREAM_H_
+
+#include "base/platform_file.h"
+#include "base/callback.h"
+
+namespace fileapi {
+
+using base::PlatformFileError;
+
+typedef base::Callback<void(PlatformFileError, int64)> ReadWriteCallback;
+typedef base::Callback<void(PlatformFileError)> StatusCallback;
+
+// Abstract class similar to net::FileStream, but supporting only
+// the asyncronous operations and not necessarily relying on PlatformFile.
+class AsyncFileStream {
+ public:
+  virtual ~AsyncFileStream() {};
+
+  virtual void Read(char* buffer,
+                    int64 length,
+                    const ReadWriteCallback& callback) = 0;
+
+  virtual void Write(const char* buffer,
+                     int64 length,
+                     const ReadWriteCallback& callback) = 0;
+
+  virtual void Seek(int64 offset,
+                    const StatusCallback& callback) = 0;
+};
+
+}  // namespace fileapi
+
+#endif  // WEBKIT_CHROMEOS_FILEAPI_ASYNC_FILE_STREAM_H_