Image Processing Failing periodically on 2nd or later image in Firefox 18.0.1 on Ubuntu

[scyclops]

I kept running into a problem where uploading a 2nd or later image periodically caused the upload to fail. By inserting lots of logging statements I tracked it down to the process method in jquery.fileupload-fp.js

My fix was to insert the below line at the very beginning of the process method.

this._processingQueue = $.Deferred().resolveWith(this).promise();

It seems the Deferred needs to be recreated every time the processing is run because once the Deferred is used it can't be reused (or at least that's my theory). It doesn't seem to fully explain why the failures were periodic (around 30% of the time the 2nd or 3rd image failed to upload). I'm also using the autoUpload: true option.

I only noticed this issue in Firefox on Ubuntu but I haven't rigorously tested to see if it occurs more widely.

[bigdave]

For what it's worth, I'm not reproducing this on OS X with Firefox 19 Beta.

[blueimp]

I could reproduce this issue and it seems that the reason was the preview rendering, which also makes use of the processing queue.
The referenced commit should fix this issue.