external URLs should be represented in upload window
when uploading from external URL, until the file is downloaded to my computer, other uploads are stuck.
only the Add files... progress bar stays open, but nothing happens.
for example:
1) add a url for a small movie, (>50MB)
2) add a small file (100k)
in normal situations, they will both appear in the upload window, and priority will be given to the small file.
In the described case, they won't appear, and small uploads have to wait, leaving their progress windows open.