Make FileStream::Seek async and add FileStream::SeekSync for sync operation

net/base/mock_file_stream.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.
 
 // This file defines MockFileStream, a test class for FileStream.
 
 #ifndef NET_BASE_MOCK_FILE_STREAM_H_
 #define NET_BASE_MOCK_FILE_STREAM_H_
 #pragma once
 
@@ skipping 12 matching lines @@
 class MockFileStream : public net::FileStream {
  public:
   MockFileStream(net::NetLog* net_log)
       : net::FileStream(net_log), forced_error_(net::OK) {}
 
   MockFileStream(base::PlatformFile file, int flags, net::NetLog* net_log)
       : net::FileStream(file, flags, net_log), forced_error_(net::OK) {}
 
   // FileStream methods.
   virtual int OpenSync(const FilePath& path, int open_flags) OVERRIDE;
-  virtual int64 Seek(net::Whence whence, int64 offset) OVERRIDE;
+  virtual int Seek(net::Whence whence, int64 offset,
+                   const Int64CompletionCallback& callback) OVERRIDE;
+  virtual int64 SeekSync(net::Whence whence, int64 offset) OVERRIDE;
   virtual int64 Available() OVERRIDE;
   virtual int Read(IOBuffer* buf,
                    int buf_len,
                    const CompletionCallback& callback) OVERRIDE;
   virtual int ReadSync(char* buf, int buf_len) OVERRIDE;
   virtual int ReadUntilComplete(char *buf, int buf_len) OVERRIDE;
   virtual int Write(IOBuffer* buf,
                     int buf_len,
                     const CompletionCallback& callback) OVERRIDE;
   virtual int WriteSync(const char* buf, int buf_len) OVERRIDE;
@@ skipping 28 matching lines @@
 
   int forced_error_;
   FilePath path_;
 };
 
 }  // namespace testing
 
 }  // namespace net
 
 #endif  // NET_BASE_MOCK_FILE_STREAM_H_