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

net/base/mock_file_stream.cc

 // 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.
 
 #include "net/base/mock_file_stream.h"
 
 namespace net {
 
 namespace testing {
 
 int MockFileStream::OpenSync(const FilePath& path, int open_flags) {
   path_ = path;
   return ReturnError(FileStream::OpenSync(path, open_flags));
 }
 
-int64 MockFileStream::Seek(Whence whence, int64 offset) {
-  return ReturnError64(FileStream::Seek(whence, offset));
+int MockFileStream::Seek(Whence whence, int64 offset,
+                         const Int64CompletionCallback& callback) {
+  return ReturnError(FileStream::Seek(whence, offset, callback));
+}
+
+int64 MockFileStream::SeekSync(Whence whence, int64 offset) {
+  return ReturnError64(FileStream::SeekSync(whence, offset));
 }
 
 int64 MockFileStream::Available() {
   return ReturnError64(FileStream::Available());
 }
 
 int MockFileStream::Read(IOBuffer* buf,
                          int buf_len,
                          const CompletionCallback& callback) {
   return ReturnError(FileStream::Read(buf, buf_len, callback));
@@ skipping 21 matching lines @@
   return ReturnError64(FileStream::Truncate(bytes));
 }
 
 int MockFileStream::Flush() {
   return ReturnError(FileStream::Flush());
 }
 
 }  // namespace testing
 
 }  // namespace net