Because of the changes that have been introduced in ResourceLoader in 1.19 (see https://bugzilla.wikimedia.org/33711 and https://bugzilla.wikimedia.org/33746 for example), on-wiki gadget users will begin to see lots of JavaScript errors if we don't act now.
On enwiki.beta (http://en.wikipedia.beta.wmflabs.org/), I enabled all the gadgets and then went through the JS errors that popped up to see what modifications needed to be made to [[MediaWiki:Gadgets-definition]]. I let [[Wikipedia talk:Gadget]] know about the needed changes (https://en.wikipedia.org/w/index.php?diff=471706835).
We need a lot more of this sort of testing on all the wikis, but I'm only one person and there are hundreds of wikis. Please have a look at http://labs.wikimedia.beta.wmflabs.org/wiki/Special:SiteMatrix and find other wikis to test.
On some wikis (yiwiki.beta, for example), we're going to need to import the MediaWiki namespace, so if you come across a wiki that is different than production, let me know or pop into #wikimedia-labs and ping one of the beta team members there.
Mark.