Add a parameter to FileStreamWriter::CreateForLocalFile to allow creating new

chrome/browser/chromeos/drive/fileapi/webkit_file_stream_writer_impl.cc

Index: chrome/browser/chromeos/drive/fileapi/webkit_file_stream_writer_impl.cc
diff --git a/chrome/browser/chromeos/drive/fileapi/webkit_file_stream_writer_impl.cc b/chrome/browser/chromeos/drive/fileapi/webkit_file_stream_writer_impl.cc
index 963c42fe80b40070ed4425b949fc8b9779781b58..63df4d1586e1fee8cd67405c1a8603604b82cebf 100644
--- a/chrome/browser/chromeos/drive/fileapi/webkit_file_stream_writer_impl.cc
+++ b/chrome/browser/chromeos/drive/fileapi/webkit_file_stream_writer_impl.cc
@@ -169,7 +169,8 @@ void WebkitFileStreamWriterImpl::WriteAfterCreateWritableSnapshotFile(
   DCHECK(!close_callback_on_ui_thread.is_null());
   close_callback_on_ui_thread_ = close_callback_on_ui_thread;
   local_file_writer_.reset(fileapi::FileStreamWriter::CreateForLocalFile(
-      file_task_runner_.get(), local_path, offset_));
+      file_task_runner_.get(), local_path, offset_,
+      fileapi::FileStreamWriter::OPEN_EXISTING_FILE));
   int result = local_file_writer_->Write(buf, buf_len, callback);
   if (result != net::ERR_IO_PENDING)
     callback.Run(result);