Health report can take 1 second on shutdown and seems to be coming from here: http://mxr.mozilla.org/mozilla-central/source/services/healthreport/healthreporter.jsm#434 Shutdown Profile: http://people.mozilla.com/~bgirard/cleopatra/#report=e063bfd09e518271bad8b1a5688aad048323e516

This is a known issue and can be marked as a dupe of one of about 3 or 4 bugs. The most likely culprit is bug 827157. That landed yesterday and should be in today's Nightly. However, my OS X Nightly didn't pick up the change for some reason. I guess the build was flaky last night. You'll see it eventually. Feel free to test on an m-c build until then.