While testing a patch from @Niedzielski I noticed that clicking the download icon doesn't lazy load images before the print action.
= QA steps
* Make sure "expand all sections" is disabled in Special:MobileOptions
* Visit https://en.m.wikipedia.beta.wmflabs.org/wiki/Qatar
* Use mobile site on a **mobile resolution** (desktop mode seems to be working fine) with sections collapsed by default
* Click the print button and print to pdf
Expected: PDF has images
Actual: PDF does not have images
= Developer notes
From the look of it it's throwing an exception as it calls:
lazyImageLoader.loadImages( lazyImageLoader.queryPlaceholders( document.getElementById( 'content' ) ) )
.then( doPrintBeforeTimeout, doPrintBeforeTimeout );
My guess is something went wrong in T214658 but someone will need to investigate and work out what.