This method synchronously returns a string. The profile in that string does not contain subprocess profiles and thus isn't very useful. There's one caller at http://searchfox.org/mozilla-central/rev/568e68ade5c6e3d29abba1d1bc25fe87fa1da962/devtools/server/performance/profiler.js#187 but I think options.stringify is never used so it can be removed.