There's no smoking gun checkin in https://treeherder.mozilla.org/#/jobs?repo=mozilla-central&fromchange=a4f512250d7d&tochange=e44ee5f26791&filter-searchStr=linux%20debug%20jetpack but instead a gradual slide over a threshold, to the point where the last time there was a green run of either Linux or Linux64 debug JP was Monday morning. That's not acceptable for a visible-by-default test suite, so I'm hiding it on all trunk trees, and then when this slow hits mozilla-aurora on Monday, there as well. The dependencies of this bug won't be all of them, I'm bound to have missed some of the less frequent ones, because there are so many, making it smell more like some systemic problem than anything in particular.
I don't know of anyone actively working on the SDK code, maybe Andy's team will do so? Otherwise I'd recommend disabling the tests that are timing out rather than hoping for someone to have the time to figure out what is going on.
Dave, if you could point me at someone who could help, that would be great.