Automated performance testing and sheriffing
We have several test harnesses that test Firefox for various performance characteristics (page load time, startup time, etc.). We also generate some metrics as part of the build process (like installer size) that are interesting to track over time. Currently we aggregate this information in the Perfherder web application where performance sheriffs watch for significant regressions, filing bugs as appropriate.
Current list of automated systems we are tracking (at least to some degree):