Try drag-and-drop any numbers of files/folders into the drop area
below, and you will see a neat file tree with a preview pain to refine your selection.
Don't worry, dropping a folder which contains millions of files
won't make your browser get stuck! (You can click 'stop scanning' to stop
scanning)
(NOTE: this page is just for demo and selected files/folders are not uploaded to anywhere)
More info: http://wiki.whatwg.org/wiki/DragAndDropEntries
This page requires Chrome 21 or later.