I know! It's in:
Keyup:
https://github.com/mozilla-b2g/gaia/pull/16572/files#diff-74841e428dea67f7357f1893a4d26155R493
Keydown:
https://github.com/mozilla-b2g/gaia/pull/16572/files#diff-74841e428dea67f7357f1893a4d26155R521

;)