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

net/base/upload_data.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/upload_data.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/file_util.h"
@@ skipping 108 matching lines @@
   int64 rv = file->OpenSync(
       file_path_,
       base::PLATFORM_FILE_OPEN | base::PLATFORM_FILE_READ);
   if (rv != OK) {
     // If the file can't be opened, we'll just upload an empty file.
     DLOG(WARNING) << "Failed to open \"" << file_path_.value()
                   << "\" for reading: " << rv;
     return NULL;
   }
   if (file_range_offset_) {
-    rv = file->Seek(FROM_BEGIN, file_range_offset_);
+    rv = file->SeekSync(FROM_BEGIN, file_range_offset_);
     if (rv < 0) {
       DLOG(WARNING) << "Failed to seek \"" << file_path_.value()
                     << "\" to offset: " << file_range_offset_ << " (" << rv
                     << ")";
       return NULL;
     }
   }
 
   return file.release();
 }
@@ skipping 145 matching lines @@
     return;
 
   for (size_t i = 0; i < elements_.size(); ++i)
     *content_length += elements_[i].GetContentLength();
 }
 
 UploadData::~UploadData() {
 }
 
 }  // namespace net