The Mozilla Toolkit is a set of APIs, built on top of Gecko, which provide advanced services to XUL applications. These services include Profile Management, Chrome Registration, Browsing History, Extension and Theme Management, Application Update Service, and Safe Mode. (More info)
meta-bug for tracking bugs that are integral to measuring responsiveness on e10s vs non-e10s, and whatever else needs to be done in order to give a go/no-go on e10s from a responsiveness standpoint.
Started as a strict subset of bug 1222849