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

webkit/fileapi/file_writer_delegate.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 "webkit/fileapi/file_writer_delegate.h"
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/file_util_proxy.h"
 #include "base/message_loop.h"
@@ skipping 162 matching lines @@
 
 void FileWriterDelegate::OnResponseStarted(net::URLRequest* request) {
   DCHECK_EQ(request_, request);
   // file_stream_->Seek() blocks the IO thread.
   // See http://crbug.com/75548.
   base::ThreadRestrictions::ScopedAllowIO allow_io;
   if (!request->status().is_success() || request->GetResponseCode() != 200) {
     OnError(base::PLATFORM_FILE_ERROR_FAILED);
     return;
   }
-  int64 error = file_stream_->Seek(net::FROM_BEGIN, offset_);
+  int64 error = file_stream_->SeekSync(net::FROM_BEGIN, offset_);
   if (error != offset_) {
     OnError(base::PLATFORM_FILE_ERROR_FAILED);
     return;
   }
   Read();
 }
 
 void FileWriterDelegate::OnReadCompleted(net::URLRequest* request,
                                          int bytes_read) {
   DCHECK_EQ(request_, request);
@@ skipping 125 matching lines @@
 
 FileSystemQuotaUtil* FileWriterDelegate::quota_util() const {
   DCHECK(file_system_operation_);
   DCHECK(file_system_operation_->file_system_context());
   DCHECK(file_system_operation_->file_system_operation_context());
   return file_system_operation_->file_system_context()->GetQuotaUtil(
       path_.type());
 }
 
 }  // namespace fileapi