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diff --git a/chromium/webkit/browser/blob/file_stream_reader.h b/chromium/webkit/browser/blob/file_stream_reader.h
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+++ b/chromium/webkit/browser/blob/file_stream_reader.h
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+// 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_BLOB_FILE_STREAM_READER_H_
+#define WEBKIT_BLOB_FILE_STREAM_READER_H_
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "net/base/completion_callback.h"
+#include "webkit/browser/webkit_storage_browser_export.h"
+
+namespace net {
+class IOBuffer;
+}
+
+namespace webkit_blob {
+
+// A generic interface for reading a file-like object.
+class WEBKIT_STORAGE_BROWSER_EXPORT FileStreamReader {
+ public:
+  // It is valid to delete the reader at any time.  If the stream is deleted
+  // while it has a pending read, its callback will not be called.
+  virtual ~FileStreamReader() {}
+
+  // Reads from the current cursor position asynchronously.
+  //
+  // Up to buf_len bytes will be copied into buf.  (In other words, partial
+  // reads are allowed.)  Returns the number of bytes copied, 0 if at
+  // end-of-file, or an error code if the operation could not be performed.
+  // If the read could not complete synchronously, then ERR_IO_PENDING is
+  // returned, and the callback will be run on the thread where Read()
+  // was called, when the read has completed.
+  //
+  // It is invalid to call Read while there is an in-flight Read operation.
+  //
+  // If the stream is deleted while it has an in-flight Read operation
+  // |callback| will not be called.
+  virtual int Read(net::IOBuffer* buf, int buf_len,
+                   const net::CompletionCallback& callback) = 0;
+
+  // Returns the length of the file if it could successfully retrieve the
+  // file info *and* its last modification time equals to
+  // expected modification time (rv >= 0 cases).
+  // Otherwise, a negative error code is returned (rv < 0 cases).
+  // If the stream is deleted while it has an in-flight GetLength operation
+  // |callback| will not be called.
+  // Note that the return type is int64 to return a larger file's size (a file
+  // larger than 2G) but an error code should fit in the int range (may be
+  // smaller than int64 range).
+  virtual int64 GetLength(const net::Int64CompletionCallback& callback) = 0;
+};
+
+}  // namespace webkit_blob
+
+#endif  // WEBKIT_BLOB_FILE_STREAM_READER_H_