No close button after exporting

[Andrew Keyes]

After performing an export, if the user has been away from the computer (while rendering) there is nothing to state that the export is complete, and the user may think that it never ran. A simple 'Close' button, should appear in place of the 'Cancel'. A pop-up message would be nice as well.

From the couple times I've stayed at my computer, I have seen the notification, but that goes away after a few seconds, and there is no clear way to close the export window (other than the [x], or the 'Cancel', but hitting that scares me into thinking that it will undo the export I just did).