See the URL http://webcam.sewanee.edu/view/view.shtml for a mpjeg webcam that is fed as a multipart resource.
The progress bar gets stuck around 90% and the spinning progress indicator on the tab never completes.
This broke between 17233 and 17241
Seems *very* likely this was http://trac.webkit.org/projects/webkit/changeset/17238
http://trac.webkit.org/projects/webkit/changeset/17236 is the only other remotely possible candidate in that range, but 17238 seems most likely by far.
CC'ing Darin, as it's likely he originally caused the regression
This was fixed (probably) in http://trac.webkit.org/projects/webkit/changeset/21782