At the moment, everything we're putting in a wasm sandbox is not
performance-critical, so we don't need PGO.  It's also not clear that
PGO would actually work properly with code that's been run through
wasm.  Let's leave figuring that out until, at the very least, the wasm
toolchain is a little more mature.

Differential Revision: https://phabricator.services.mozilla.com/D58513

--HG--
extra : moz-landing-system : lando