FileDownloader problem

I started migrate from 6 to 7 and strange behavior noticed in FileDownloader class (latest vaadin release).
In order to download file through button click, I have to click button twice first time!
After button clicked twice next clicks react normal. If we try download file “old style”
way(Page.getCurrent().open(resource, “_self”, false)) download start immediatly at first time, but UI
enters a state after which does not respond to user input. Saves only refresh browser.
Has anyone seen or what to do?

Here is example project (29 KB)