seen in test2wiki/mw.o since 15 May and also beta labs
Pick any page for example http://test2.wikipedia.org/wiki/LowTemplate
Click Download as PDF
Get the Rendering page showing 1% progress.
Rendering page never refreshes.
Note that the Rendering page does say "This page should automatically refresh every few seconds. If this does not work, please press your browser's refresh button." and upon refreshing the page the PDF file is available for download.